JP5628233B2 - Motor drive device, fluid compression system, and air conditioner - Google Patents

Description

  The present invention relates to a motor drive device, a fluid compression system, and an air conditioner.

  The air conditioner rotates an indoor fan installed in the indoor unit to send indoor air to the heat exchanger, heat exchanges with the refrigerant flowing through the heat exchanger, and heats or cools the air. Air conditioning is performed by blowing air into the room. In addition, a compressor constituting a part of the heat pump cycle is installed in the outdoor unit of the air conditioner, and the refrigerant is compressed by the compressor and discharged at a high temperature and a high pressure.

Moreover, as a permanent magnet with which the motor of a compressor is provided, a ferrite magnet is used when importance is attached to a price, and rare earth magnets, such as a neodymium magnet, are used when importance is attached to a performance. Incidentally, ferrite magnets tend to demagnetize in low temperature environments, and rare earth magnets tend to demagnetize at high temperatures. Here, “demagnetization” means that the magnetic moment of the entire magnet decreases due to a temperature rise due to eddy current loss of the magnet, a reverse magnetic field due to a current flowing into the coil, or the like.
By the way, in an environment where an air conditioner is used, the temperature around the motor inside the compressor is very low at the start of the heating operation in winter and is almost the same as the outside air temperature, and is operated in high temperature outside air during the cooling operation in summer. It becomes very hot.

Therefore, the compressor installed in the outdoor unit is inevitably driven in a low temperature environment or a high temperature environment, and a high driving capability is required. If a high driving capability is to be exhibited in accordance with an operation request based on the room temperature or the outdoor temperature, the current flowing through the motor increases. As a result, the permanent magnet (ferrite magnet or rare earth magnet) included in the motor may be demagnetized.
In addition to demagnetization, in order to prevent destruction of the switching element installed in the inverter circuit, it is necessary to suppress the current flowing through the switching element to a predetermined allowable current value or less.

The following techniques are known as conventional techniques for partially addressing these problems.
For example, in Patent Document 1, a motor phase current is calculated by a phase current calculation unit (current reproduction unit) based on an output of a DC current detection circuit (current detector), and the motor phase current becomes a predetermined threshold value or more. A brushless motor driving device for a compressor having a current limiting function for lowering the frequency of a brushless motor (motor) in this case is described.
In the technique described in Patent Literature 1, the demagnetization of the permanent magnet is prevented by changing the overcurrent protection stop threshold determined by the voltage comparison circuit to a predetermined value that is less than the demagnetization current.

  In Patent Document 2, the control circuit controls the IGBT (Insulated Gate Bipolar Transistor) on / off to drive the motor, and when the current limit command signal is input from the current limit circuit, the IGBT is turned off. A technique for cutting off the motor current is described. The current limiting circuit described above outputs a current limiting command signal to the control circuit when the load current exceeds a predetermined overcurrent upper limit value. This prevents demagnetization of the permanent magnet provided in the motor.

JP 2009-198139 A Japanese Patent Application Laid-Open No. 07-337072

When a short-circuit current flows through the inverter circuit due to malfunction or the like, it is necessary to stop the inverter circuit instantaneously (generally within several μsec) in order to prevent the switching element from being destroyed.
However, in the techniques described in Patent Documents 1 and 2, since the stop instruction to the inverter circuit is performed via the microcomputer, a delay of the microcomputer cycle time (approximately 10 to several hundred μsec) occurs. Therefore, it is necessary to set the operation threshold value of the overcurrent protection means to be lower than the original threshold value in anticipation of the cycle time. Note that this problem can be avoided if a microcomputer with a short cycle time is used, but a microcomputer with a cycle time of several μsec is more expensive than that used for a normal home appliance. Therefore, if such a microcomputer is mounted on an air conditioner, the price competitiveness of the product is reduced.

  Then, the subject of this invention is providing a highly reliable motor drive device, a fluid compression system, and an air conditioner.

In order to solve the above problems, the present invention provides an element short circuit protection that stops driving of a switching element when a current value input from a current detection unit exceeds a short circuit protection threshold for preventing a short circuit in an inverter circuit. And a control unit estimates a motor current flowing into the motor from a current value input from the current detection unit, and the motor current relates to temperature protection of the switching element and / or demagnetization protection of the motor. A process of stopping the driving of the switching element when another current threshold is exceeded, and the current value detected by the current detection means is input to the element short-circuit protection means, and an arithmetic process related to the control means is input to the microcomputer for processing of the serial element short-circuit protection means is performed without involvement of the microcomputer, the control Processing stage is characterized in that it is performed by interposing the microcomputer.

  According to the present invention, a highly reliable motor drive device, fluid compression system, and air conditioner can be provided.

1 is a system configuration diagram including a motor drive device according to a first embodiment of the present invention. (A) is a flowchart which shows the flow of a process of an overcurrent determination part, (b) is a flowchart which shows the flow of a process of an element short circuit protection means. It is explanatory drawing which shows typically the time change of the motor current when the short circuit current flows into the inverter circuit. It is a system block diagram containing the motor drive device which concerns on 2nd Embodiment of this invention. 5 is a graph showing changes in element absolute rating, motor demagnetization current, motor demagnetization protection threshold, and element short circuit protection threshold with respect to motor winding temperature in a motor using a permanent magnet having low temperature demagnetization characteristics. 5 is a graph showing changes in element absolute rating, motor demagnetization current, motor demagnetization protection threshold, and element short circuit protection threshold with respect to motor winding temperature in a motor using a permanent magnet having high temperature demagnetization characteristics. It is a system block diagram containing the motor drive device which concerns on 3rd Embodiment of this invention. It is a graph which shows the change of the element absolute rating with respect to the element temperature of the switching element which an inverter circuit has, element short circuit protection threshold value, temperature breakdown current value, element temperature protection threshold value, and current limitation threshold value. It is a flowchart which shows the flow of a process of the element temperature protection overcurrent determination part with which the motor drive device which concerns on 3rd Embodiment of this invention is provided. It is a system block diagram containing the motor drive device which concerns on 4th Embodiment of this invention.

  Embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

<< First Embodiment >>
<System configuration>
FIG. 1 is a system configuration diagram including a motor drive device according to a first embodiment of the present invention.
The AC power source 200 indicates a power source of AC power transmitted / distributed from a power plant (not shown) or the like.
Converter circuit 300 is a circuit that converts an AC voltage input from AC power supply 200 into a DC voltage, and includes an diode bridge in which diodes D1 and D3 are connected in series in the forward direction and the interconnection point is the converter input terminal. ing. The same applies to the diodes D2 and D4. Further, a smoothing capacitor C for smoothing the pulsating component included in the DC voltage is connected in parallel with the diode bridge.
The AC power supply 200 and the converter circuit 300 connected to the AC power supply 200 constitute a “DC power supply”.

The motor driving device 100 converts the DC voltage input from the converter circuit 300 into a predetermined AC voltage by inverter control, and outputs it to the motor M. Details of processing performed by the motor drive device 100 will be described later.
The motor M is a permanent magnet type synchronous motor, for example, and is connected to the inverter circuit 11 via a three-phase winding. That is, the motor M rotates by attracting a permanent magnet (not shown) as a rotor by a rotating magnetic field generated by an alternating current flowing into the three-phase winding. In addition, the motor M is used for the compressor (not shown) which comprises the heat pump cycle of an air conditioner (not shown), for example.

<Configuration of motor drive device>
As shown in FIG. 1, the motor drive device 100 includes a power module 10, a current detector 20, an amplifier 30, and inverter control means 40.
The power module 10 includes an inverter circuit 11 including a plurality of switching elements (not shown) for outputting a predetermined AC voltage to the motor M, element short-circuit protection means 12 for protecting the switching elements, and a switching element. The inverter drive circuit 13 for driving is integrated and integrated.
The current detector (current detection means) 20 is connected in series to the bus line between the converter circuit 300 and the inverter circuit 11, detects a DC current supplied to the inverter circuit 11, and the amplifier 30 and the element short-circuit protection means 12. Output every moment.

The amplifier 30 includes, for example, a transistor, amplifies the detection signal input from the current detector 20, and outputs the amplified detection signal to the motor current reproduction unit 41 of the inverter control unit 40.
The inverter control means (control means) 40 calculates an AC voltage to be applied to the motor M based on the detection signal input from the amplifier 30 and the rotational speed command value ω of the motor M, and converts it into a drive signal. Output.
The rotational speed command value ω is determined based on set temperature information input from a remote controller (not shown), an indoor temperature detected by a thermistor (not shown) of an indoor unit (not shown), and the like. The rotational speed command value of the motor M.

(1. Power module)
The power module 10 includes an inverter circuit 11, an element short circuit protection means 12, and an inverter drive circuit 13.
The inverter circuit 11 has a plurality of switching elements (not shown), and switches each of the switching elements on and off in accordance with the PWM signal input from the inverter drive circuit 13 so that a predetermined three-phase AC voltage is supplied to the motor M. Output to. And the three-phase alternating current according to the said three-phase alternating voltage flows into the motor M, and generates the above-mentioned rotating magnetic field.
As the switching element included in the inverter circuit 11, for example, an IGBT can be used.

The element short-circuit protection means 12 compares the current detection value input from the current detector 20 with a preset element short-circuit protection threshold, and when the current detection value exceeds the element short-circuit protection threshold, a stop command signal Is output to the inverter drive circuit 13.
Note that the processing of the element short-circuit protection means 12 is executed without a microcomputer.
The inverter drive circuit 13 outputs a PWM signal (Pulse Width Modulation) to each switching element (not shown) of the inverter circuit 11 in accordance with the drive signal input from the drive signal generator 44. . Further, when a stop command signal is input from the element short circuit protection means 12, the inverter drive circuit 13 stops outputting the PWM signal.

(2. Inverter control means)
The inverter control means (control means) 40 includes a motor current reproduction unit 41, a speed command unit 42, an overcurrent determination unit 43, and a drive signal generation unit 44. Note that the processing of the inverter control means 40 is executed by a microcomputer (or via a microcomputer). The microcomputer includes an electronic circuit (not shown) such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various interfaces, and reads a program stored in the ROM. The data is expanded in the RAM, and the CPU executes various processes.

The motor current reproduction unit 41 reproduces the current flowing through the motor M (hereinafter referred to as motor current) based on the detection signal detected by the current detector 20 and amplified by the amplifier 30, and the overcurrent determination unit 43. Output to.
The speed command unit 42 includes a three-phase AC command voltage to be applied to the motor M and a PWM frequency based on the motor current input from the motor current reproduction unit 41 and the rotational speed command value ω input from the outside. The command value is calculated and output to the drive signal generator 44.

The overcurrent determination unit 43 compares the motor current input from the motor current reproduction unit 41 with the overcurrent threshold (other threshold) stored in the microcomputer, and the motor current exceeds the overcurrent threshold. In this case, a stop command signal is output to the drive signal generator 44. Details of the overcurrent threshold will be described later.
The drive signal generator 44 generates a drive signal based on the command value input from the speed command unit 42 and outputs the drive signal to the inverter drive circuit 13. When the stop command signal is input from the overcurrent determination unit 43, the drive signal generation unit 44 stops the drive signal generation process according to the command.

Hereinafter, the determination process performed by the overcurrent determination unit 43 and the determination process performed by the element short-circuit protection unit 12 will be sequentially described.
Incidentally, the overcurrent determination unit 43 performs a determination process on an actual abnormality (such as a step-out of the motor M) that occurs after a lapse of several msec or more after detecting an abnormality sign. On the other hand, the element short-circuit protection means 12 performs a determination process on an actual abnormality (such as a short circuit of the inverter circuit 11) after several μsec has elapsed.

<Processing of overcurrent determination unit>
As described above, the overcurrent determination unit 43 compares the motor current input from the motor current reproduction unit 41 with the overcurrent threshold stored in the microcomputer, and determines that the motor current is an overcurrent threshold (other thresholds). ), The processing of the drive signal generator 44 is stopped.
The processing of the overcurrent determination unit 43 is executed by a microcomputer (not shown). Therefore, the overcurrent determination unit 43 can perform highly accurate determination using a complicated calculation formula. Note that the computation time of the microcomputer required for the determination processing performed in this embodiment is 10 μsec to several hundred μsec.

Incidentally, from the detection of the overcurrent in the inverter circuit 11 by the current detector 20, time Delta] t _p of the inverter control means 40 to stop the operation of the inverter circuit 11 is as follows.
That is, the time Δt _p is determined as the time Δt _p 1 until the signal from the current detector 20 is input to the inverter control means 40 and the inverter control means 40 is determined to be an overcurrent, and the drive signal generator 44 is turned on. This is the sum of the time Δt _p 2 until stopping and the time Δt _p 3 until the inverter circuit 11 is actually turned off after receiving the drive signal stop of the inverter control means 40, and is shown below (Formula 1) )become that way.

Δt _p = Δt _p 1 + Δt _p 2 + Δt _p 3 (Expression 1)

Here, the current detector 20, the current detector 20 to the inverter control means 40, the inverter control means 40 to the inverter circuit 11, and the inverter circuit 11 are so-called hardware that does not interpose a microcomputer. It consists of a circuit. Therefore, the time Δt _p 1 until the signal from the current detector 20 is transmitted to the inverter control means 40 and the time Δt _p 3 until the inverter circuit 11 is turned off upon receiving the drive signal stop of the inverter control means 40 are: Each is several μsec.

On the other hand, the inverter control means 40 executes a process from when the detection signal from the current detector 20 is input to when the stop command signal is output to the inverter drive circuit 13 by a microcomputer (not shown). It takes 100 μsec. Then, the a time Delta] t _p also 10μsec~ several hundred μsec shown in (Equation 1).
Therefore, the process of the overcurrent determination unit 43 using a microcomputer is suitable for determination of characteristics that take several milliseconds or more from the detection of an abnormality (predictive sign), such as the above-described step-out, until the influence is exerted. Yes.

  For example, as suitable for the determination process by the overcurrent determination unit 43 using a microcomputer, step-out protection of the motor M, winding temperature protection of the motor M, demagnetization protection of the motor M, switching element (not shown) Temperature rise protection, compressor (not shown) overtemperature protection, compressor pressure protection, and the like. These characteristics can sufficiently cope with processing using a microcomputer because it takes several msec or more until an abnormality occurs due to an electrical time constant or heat capacity.

In such determination processing, control information such as the amplitude and phase of the motor current, the amplitude and phase of the motor applied voltage, and the DC voltage value and current value input to the inverter circuit 11 can be used.
Also, a room temperature thermistor (not shown), an outside temperature thermistor (not shown), a frosting thermistor (not shown), a discharge temperature thermistor (not shown), a human detection sensor (not shown), a thermopile (not shown) The sensor information acquired from the above may be used.

In the present embodiment, as an example of the determination process by the overcurrent determination unit 43, a sign (that is, an increase in current input from the current detector 20) when the motor M steps out is detected and the motor M is stopped. The case will be described.
As described above, the synchronous motor rotates by attracting the rotor (permanent magnet) by the rotating magnetic field generated by the alternating current. However, in the case of an overload or a sudden speed change, the synchronization between the PWM signal input from the inverter drive circuit 13 and the rotation of the motor M may be lost and step out may occur.

  Here, immediately before the step-out occurs in the motor M, the difference between the applied voltage and the motor induced voltage becomes large. For example, when voltage / current phase control is performed by vector control, the motor current increases over a period of several hundred msec immediately before the step-out of the motor M occurs.

Therefore, the overcurrent determination unit 43 compares a predetermined overcurrent determination threshold value (other threshold value) stored in advance with the motor current value, and generates a drive signal when the motor current value exceeds the overcurrent determination threshold value. The processing of the unit 44 is stopped. As a result, the motor driving apparatus 100 can stop the driving of the motor M immediately when the step-out (predictive sign) is detected.
Incidentally, the overcurrent determination threshold value may be a preset constant value, or the overcurrent determination unit 43 may determine an optimum overcurrent determination threshold value based on a phase shift between the applied voltage of the motor M and the induced voltage. May be calculated.

FIG. 2A is a flowchart showing a flow of processing performed by the overcurrent protection determination unit. In the following description, the ON / OFF operation of the switching element of the inverter circuit 11 in response to the PWM signal from the inverter driving circuit 13 may be simply referred to as “switching element driving”. Further, it is assumed that the switching element is driven at the start of the flowchart shown in FIG.
In step S101, the overcurrent determination unit 43 determines whether or not a predetermined time Δt _A has elapsed from the start of processing. The predetermined time Δt _A is a cycle time of the microcomputer that executes the processing of the overcurrent determination unit 43, and is a preset value.
When the predetermined time Δt _A has elapsed from the start of the process (S101 → Yes), the process of the overcurrent determination unit 43 proceeds to step S102. On the other hand, when the predetermined time Δt _A has not elapsed since the start of the process (S101 → No), the overcurrent determination unit 43 repeats the process of step S101.

Overcurrent determination unit 43 in step S102, the motor current value I _M which is inputted from the motor current reproduction unit 41 determines whether or not larger than a predetermined over-current threshold I _{E (other} thresholds).
When the motor current value _IM is larger than the overcurrent threshold _IE (S102 → Yes), the process of the overcurrent determination unit 43 proceeds to step S103. On the other hand, the motor current value _{I M} is less than or equal to the over-current threshold _{I E} (S102 → No), the processing of the overcurrent determination unit 43 returns to START.
In step S103, the overcurrent determination unit 43 stops driving the switching element. As a result, power supply to the motor M is stopped and the motor M is stopped.

<Processing of element short-circuit protection means>
FIG. 2B is a flowchart showing the flow of processing performed by the element short-circuit protection unit. Note that the switching element of the inverter circuit 11 is driven at the start of the flowchart.
In step S201, the element short-circuit protection unit 12 determines whether or not a predetermined time Δt _B has elapsed from the start of processing. The predetermined time Δt _B is the cycle time of the element short-circuit protection means 12 and is a preset value.
When the predetermined time Δt _B has elapsed from the start of the process (S201 → Yes), the process of the element short-circuit protection unit 12 proceeds to step S202. On the other hand, when the predetermined time Δt _B has not elapsed since the start of the process (S201 → No), the element short-circuit protection unit 12 repeats the process of step S201.

Element short-circuit protection means in step S202 12 is the current detection value I _S inputted from the current detector 20 determines whether the larger element short-circuit protection threshold I _D.
When the current detection value _IS is larger than the element short-circuit protection threshold _ID (S202 → Yes), the process of the element short-circuit protection unit 12 proceeds to step S203. On the other hand, if the current detection value _{I S} is less than or equal to element short-circuit protection threshold _{I D} (S202 → No), the processing element short-circuit protection means 12 returns to START.
In step S203, the element short-circuit protection means 12 outputs a stop command signal to the inverter drive circuit 13. When a stop command signal is input from the element short-circuit protection means 12, driving of the switching element of the inverter drive circuit 13 is stopped, and as a result, driving of the motor M is also stopped.

  The switching element drive stop process based on the determination result of the overcurrent determination unit 43 and the switching element drive stop process based on the determination result of the element short-circuit protection means 12 are executed independently of each other. For example, when the stop process by the element short-circuit protection unit 12 is executed before the stop process by the overcurrent determination unit 43, the motor M stops using the stop command signal output from the element short-circuit protection unit 12 as a trigger.

<Effect>
According to the motor drive device 100 according to the present embodiment, a comparison determination process using a microcomputer for characteristics (such as step-out) that take several msec or more from when an abnormal sign is detected until the effect is actually realized. And the driving of the switching element is stopped as necessary. Therefore, since complicated calculation can be executed by the microcomputer using the control information and sensor information about the motor M, highly accurate determination processing can be performed.
That is, since the timing at which the step-out occurs is later than the timing at which the microcomputer processing ends, the driving of the motor M can be stopped before the step-out occurs.

Further, as described above, the time from when the element short-circuit protection means 12 detects an overcurrent until the stop command signal is output to the inverter drive circuit 13 is the time required for a hardware circuit without a microcomputer (for example, 3 μsec). Therefore, it is extremely short. Thereby, when the current detected by the current detector 20 exceeds the element short circuit protection threshold _ID , the stop command by the element short circuit protection means 12 is output earlier than the stop command by the motor demagnetization protection overcurrent determination unit 46. The Therefore, destruction of the switching element due to the short-circuit current can be reliably prevented.

FIG. 3 is an explanatory view schematically showing a temporal change of the motor current when a short-circuit current flows through the switching element. Consider a case in which the motor current suddenly increases from time t ₀ shown in FIG. 3 and a current value I ₁ exceeding the element short-circuit protection threshold _ID is detected by the current detector 20 at time t ₁ .
Note that the element absolute rating I _R shown in FIG. 3, a preset value as a current value by the motor current must not exceed even for an instant.

In this case, the driving of the switching element is stopped by the element short-circuit protection means 12 at time t ₂ after the time Δt _q (= several μsec) from time t ₁ . As a result, the time t ₂ later (see the solid line arrows in FIG. 3) the motor current decreases rapidly, it can be avoided that the motor current reaches the element absolute rating I _R. Note that the time period Δt _q is shorter than the time period (short circuit resistance) that a switching element such as an IGBT can withstand a short circuit current.
In contrast, if in the case of performing the determination processing of the element short-circuit protection threshold microcomputer time _{t 1} from the time Δt _p (= 10μsec~ several hundred .mu.sec) at time _{t 3} when is later drive stop of the switching element to be, it flows through the motor current I ₃ that exceeds the element absolute rating I _R (see dashed arrows in FIG. 3), thus leading to breakdown of the switching element.

  According to the motor drive device 100 according to the present embodiment, the element short-circuit protection unit 12 is provided outside the inverter control unit 40, which is a microcomputer, and the determination process is executed without the microcomputer. As a result, it is possible to quickly catch the rise of current when the inverter circuit 11 is short-circuited, stop driving the switching element in the middle of the rise, and reliably prevent the switching element from being destroyed.

  In addition, since electronic circuits handle weak currents, they are easily affected by noise. In the motor drive device 100 according to the present embodiment, the driving of the switching element can be quickly stopped in a time of several μsec. Therefore, the element short-circuit protection threshold value can be set to a value that can determine that a short circuit has occurred reliably in the inverter circuit 11. That is, since the element short-circuit protection threshold can be raised to near the element absolute rating, malfunction due to noise (stop of the motor M) can be eliminated.

<< Second Embodiment >>
The motor drive device 100A according to the second embodiment includes a motor demagnetization protection overcurrent determination unit 46 instead of the overcurrent determination unit 43 described in the first embodiment, and further includes a motor winding temperature detector 50, Although the motor demagnetization protection threshold setting unit 45 is different, the other points are the same as in the first embodiment. Therefore, the different part will be described, and the description of the overlapping part will be omitted.

<Configuration of motor drive device>
FIG. 4 is a system configuration diagram including a motor driving device.
The motor winding temperature detector (winding temperature detection means) 50 detects the motor winding temperature of the motor M and outputs it to the motor demagnetization protection threshold setting unit 45 every moment.
The motor demagnetization protection threshold setting unit 45 sets a demagnetization protection threshold (other threshold) for preventing demagnetization of the permanent magnet according to the motor winding temperature input from the motor winding temperature detector 50. To do. The processing performed by the motor demagnetization protection threshold setting unit 45 will be described later.

  The motor demagnetization protection overcurrent determination unit 46 demagnetizes the motor M based on the motor current input from the motor current reproduction unit 41 and the demagnetization protection threshold input from the motor demagnetization protection threshold setting unit 45. It is determined whether an overcurrent exceeding the protection threshold is flowing. When it is determined that an overcurrent exceeding the demagnetization protection threshold flows through the motor M, the motor demagnetization protection overcurrent determination unit 46 stops the process of the drive signal generation unit 44.

<Low temperature demagnetization characteristics>
(1. Setting of motor demagnetization protection threshold)
In the following description, the motor current value when demagnetization occurs in the permanent magnet of the motor M is referred to as “motor demagnetization current”.
When the permanent magnet is exposed to an excessive reverse magnetic field, the permanent magnet is demagnetized to weaken its magnetism and the properties of the magnet deteriorate. That is, when an excessive current flows through the permanent magnet used in the motor M, demagnetization occurs due to a reverse magnetic field generated by the current. Therefore, it is necessary to prevent an overcurrent greater than the motor demagnetization current from flowing into the motor M.

The motor demagnetization protection threshold value setting unit 45 sets a demagnetization protection threshold value (another threshold value) that serves as a threshold value when driving of the switching element is stopped based on the detected temperature input from the motor winding temperature detector 50. To the motor demagnetization protection overcurrent determination unit 46.
Incidentally, the processing of the motor demagnetization protection threshold setting unit 45 is executed by a microcomputer.

FIG. 5 is a graph showing changes in element absolute rating, motor demagnetization current, motor demagnetization protection threshold, and element short circuit protection threshold with respect to motor winding temperature in a motor using a permanent magnet having low temperature demagnetization characteristics. .
As shown in FIG. 5, a permanent magnet (for example, a ferrite magnet) having a low-temperature demagnetization characteristic has a motor demagnetization current value that decreases as the temperature decreases (that is, it becomes easier to demagnetize).

Therefore, the motor demagnetization protection threshold setting unit 45 sets the motor demagnetization protection threshold to be smaller as the motor winding temperature becomes lower.
The motor demagnetization protection threshold is set to be smaller than the value of the motor demagnetization current at an arbitrary motor winding temperature. Incidentally, in the example shown in FIG. 5, in order to simplify the processing of the microcomputer software, the temperature characteristic of the motor demagnetization protection threshold is represented by a plurality of line segments.

(2. Setting of element short-circuit protection threshold)
Element short-circuit protection means 12, the element short-circuit protection threshold I _D for preventing a short circuit of the switching elements of the inverter circuit 11 is set to a predetermined value lower than the element absolute rating I _R (see FIG. 5). The element short circuit protection threshold _ID is set as a constant value regardless of the temperature of the motor winding.
Also in the present embodiment, as in the first embodiment, the element short-circuit protection unit 12 executes the process without using a microcomputer, and stops driving the switching element when the motor current exceeds the element short-circuit protection threshold _ID . .

In the example shown in FIG. 5, in a region where the motor winding temperature T ₀ or higher, the motor demagnetization protection threshold I _M is a constant value that is smaller than the element short-circuit protection threshold I _D by a predetermined value ΔI 1 (= I _D −I ₀ ). Is set as This is because, when the motor current exceeds the element short-circuit protection threshold _ID , the element short-circuit protection means 12 stops driving the inverter circuit 11 before the motor demagnetization protection overcurrent determination unit 46.
By the way, the motor demagnetization protection threshold has a temperature region (for example, a high temperature region) that exceeds the element short circuit protection threshold, and in other temperature regions (for example, the low temperature region), the motor demagnetization protection threshold is equal to or less than the element short circuit protection threshold. You may set so that.

<High temperature demagnetization characteristics>
FIG. 6 is a graph showing changes in element absolute rating, motor demagnetization current, motor demagnetization protection threshold, and element short circuit protection threshold with respect to motor winding temperature in a motor using a permanent magnet having high temperature demagnetization characteristics. .
As shown in FIG. 6, a permanent magnet (for example, a neodymium magnet) having a high temperature demagnetization characteristic has a motor demagnetization current value that decreases as the temperature increases (that is, it becomes easier to demagnetize).

Accordingly, the motor demagnetization protection threshold value setting unit 45 sets the demagnetization protection threshold value to be small because the motor winding temperature becomes high.
Incidentally, in the example shown in FIG. 6, showing the temperature characteristics of the motor demagnetization protection threshold as a plurality of line segments, the motor winding temperature T ₂ less area than the element temperature protection threshold I _D the motor demagnetization protection threshold It is set as the ΔI2 ₍₌ I 2 -I _D) by predetermined high value. The motor winding temperature is higher region than the temperature T ₃ is set to the element short-circuit protection threshold is greater than the motor demagnetization protection threshold.
The permanent magnet having high temperature demagnetization characteristics is not limited to a neodymium magnet but may be other rare earth magnets.

<Operation of motor drive device>
The motor demagnetization protection threshold setting unit 45 sets the characteristic motor demagnetization protection threshold shown in FIG. 5 in accordance with the motor winding temperature input from the motor winding temperature detector 50, and determines the motor demagnetization protection overcurrent. The threshold information is output to the unit 46 momentarily.
Then, the motor demagnetization protection overcurrent determination unit 46 compares the motor current input from the motor current reproduction unit 41 with the motor demagnetization protection threshold input from the motor demagnetization protection threshold setting unit 45.

When the motor current exceeds the motor demagnetization protection threshold, the motor demagnetization protection overcurrent determination unit 46 stops the processing of the drive signal generation unit 44. As a result, the driving of the switching element is stopped, the supply of electric power to the motor M is stopped, and the motor M is stopped.
On the other hand, when the motor current is less than or equal to the motor demagnetization protection threshold, the motor demagnetization protection overcurrent determination unit 46 repeats the comparison process every predetermined time.

<Effect>
According to the motor drive device 100A according to the present embodiment, with respect to the motor M including a permanent magnet having a low-temperature demagnetization characteristic such as a ferrite magnet or a high-temperature demagnetization characteristic such as a neodymium magnet, a current flowing through the motor winding is obtained from the motor. It can be less than the demagnetizing current, and the demagnetization of the permanent magnet can be reliably prevented. That is, for the demagnetization characteristic having a relatively large time constant, the driving of the switching element is stopped after performing highly accurate determination processing under the control of the microcomputer.

Thereby, as shown in FIGS. 5 and 6, the motor demagnetization protection threshold value can be finely determined according to the motor winding temperature. That is, since the maximum current according to the motor winding temperature can be passed through the motor winding while preventing demagnetization of the motor M, the capability of the motor M can be maximized.
On the other hand, when the circuit needs to be shut down in a short time, such as when the switching element is short-circuited, the driving of the switching element is stopped by a circuit (element short-circuit protection means 12) without a microcomputer.
Thus, demagnetization of the permanent magnet included in the motor M can be prevented and the switching element of the inverter circuit 11 can be appropriately protected.

Further, the correlation between the motor winding temperature and the motor demagnetization protection threshold can be determined by a plurality of parameters. That is, only by changing these constants according to the motor M to be driven, it is possible to deal with a plurality of types of permanent magnets using the same microcomputer software, and the development of the microcomputer software can be simplified. 1 or more curves the temperature characteristics of the motor demagnetization protection threshold expressed as (including linear), at the predetermined temperature T ₀ or more regions is set the motor demagnetization protection threshold to a constant value I _M (see FIG. 5) . Therefore, the processing load on the microcomputer can be reduced.

«Third embodiment»
The motor drive device 100B according to the third embodiment includes an element temperature protection overcurrent determination unit 48 instead of the overcurrent determination unit 43 described in the first embodiment, and further includes an element temperature detector 60 and an element temperature protection. Although the point provided with the threshold value setting part 47 differs, others are the same as that of 1st Embodiment. Therefore, the different part will be described, and the description of the overlapping part will be omitted.

<Configuration of motor drive device>
FIG. 7 is a system configuration diagram including a motor driving device.
The element temperature detector (element temperature detection means) 60 detects the temperature of the switching element provided in the inverter circuit 11 and outputs the detected element temperature to the element temperature protection threshold setting unit every moment.
The element temperature protection threshold value setting unit 47 sets an element temperature protection threshold value (another threshold value) according to the element temperature input from the element temperature detector 60. Details of processing performed by the element temperature protection threshold setting unit 47 will be described later.

The element temperature protection overcurrent determination unit 48 protects the motor M from the element temperature protection based on the motor current input from the motor current reproduction unit 41 and the element temperature protection threshold input from the element temperature protection threshold setting unit 47. It is determined whether or not an overcurrent exceeding the threshold value is flowing. When an overcurrent exceeding the element temperature protection threshold flows through the motor M, the element temperature protection overcurrent determination unit 48 stops the process of the drive signal generation unit 44.
Incidentally, the processing of the element temperature protection threshold setting unit 47 is executed by a microcomputer.

  On the other hand, the element short-circuit protection means 12 performs the same processing as in the first embodiment. That is, when the current detected by the current detector 20 exceeds the short-circuit protection threshold, the element short-circuit protection unit 12 stops the driving of the switching element with a circuit that does not include a microcomputer so as to stop the inverter circuit 11 quickly. As a result, when a short circuit occurs in the inverter circuit 11, the driving of the switching element is promptly stopped, and the destruction of the switching element can be reliably prevented.

FIG. 8 is a graph showing changes in element absolute rating, element short circuit protection threshold, temperature breakdown current value, element temperature protection threshold, and current limit threshold with respect to the element temperature of the switching element included in the inverter circuit.
As shown in FIG. 8, the element short circuit protection threshold is set at a current value lower than the element absolute rating. Further, the element temperature breakdown current value is a current value that leads to breakdown of the switching element when a current greater than the current value flows. The element temperature protection threshold is set as a current value smaller than the element temperature breakdown current value by a predetermined value. The current limit threshold is a threshold for decelerating the motor M, and is set as a current value that is smaller than the element temperature protection threshold by a predetermined value.

  As shown in FIG. 8, an area that is equal to or higher than the element temperature protection threshold and less than the element temperature breakdown current value is set as a “stop area”. In addition, an area that is equal to or greater than the current limit threshold and less than the element temperature protection threshold is set as a “deceleration area”. In addition, a region less than the current limit value is set as a “steady region”.

FIG. 9 is a flowchart showing an operation flow of the element temperature protection overcurrent determination unit.
In step S301, the element temperature protection overcurrent determination unit 48 determines whether or not a predetermined time Δt _C has elapsed since the start of processing. The predetermined time Δt _C is a cycle time of the microcomputer that executes the process of the element temperature protection overcurrent determination unit 48, and is a preset value.
When the predetermined time Δt _C has elapsed from the start of the process (S301 → Yes), the process of the element temperature protection overcurrent determination unit 48 proceeds to step S302. On the other hand, if the predetermined time Δt _C has not elapsed since the start of the process (S301 → No), the element temperature protection overcurrent determination unit 48 repeats the process of step S301.

Element temperature protection overcurrent determination unit 48 in step S302, the motor current value I _M which is inputted from the motor current reproduction unit 41 determines whether or not larger than the element temperature protection threshold I _T. If the motor current value _{I M} is larger than the element temperature protection threshold _{I T} (S302 → Yes), the processing of the element temperature protection overcurrent determination unit 48 proceeds to step S303. On the other hand, if the motor current value _{I M} is less than or equal to the element temperature protection threshold _{I T} (S302 → No), the processing of the element temperature protection overcurrent determination unit 48 proceeds to step S304.
In step S303, the element temperature protection overcurrent determination unit 48 stops the process of the drive signal generation unit 44. That is, the element temperature protection overcurrent determination unit 48 stops driving the switching element.
Incidentally, when the motor current is equal to or smaller than the element short circuit protection threshold and larger than the element temperature protection threshold, the element short circuit protection means 12 configured by a hard circuit does not operate.

Step element temperature protection overcurrent determination unit 48 in S304, it is determined whether or not the motor current value I _M is a current greater than the limit threshold I _L. If the motor current value _{I M} is a current greater than the limit threshold _{I L} (S304 → Yes), the processing of the element temperature protection overcurrent determination unit 48 proceeds to step S305. On the other hand, the motor current value _{I M} is processing when it is less than the current limit threshold _{I L} (S304 → No), the element temperature protection overcurrent determination unit 48 returns to STRAT.
In step S305, the element temperature protection overcurrent determination unit 48 outputs a predetermined command signal to the drive signal generation unit 44 in order to decelerate the motor M.

<Effect>
According to the motor drive device 100B according to the present embodiment, a comparison / determination process using a microcomputer is performed for the temperature characteristics of a switching element that takes several msec or more from when an abnormality (predictor) is detected until the abnormality actually occurs. And the driving of the switching element is stopped as necessary. Further, since the element temperature protection threshold used when the comparison process is performed is determined according to the element temperature input from the element temperature detector 60, it is possible to determine the overcurrent with high accuracy.
Since the switching element has a predetermined heat capacity, the driving of the motor M can be stopped before the switching is destroyed due to the temperature rise.

  Further, the element temperature protection threshold value setting unit 47 has a predetermined arithmetic expression for associating the element temperature protection threshold value with the element temperature and the element temperature protection threshold value by one or more curves (including a straight line) as shown in FIG. It is set in advance. Therefore, since the setting can be easily changed by setting the constant of the arithmetic expression to an appropriate value, the microcomputer software can be made the same for different types of inverter circuits 11, and the product development procedure can be simplified. Can do.

  If the motor current is within the circuit deceleration region (see FIG. 8), the element temperature protection overcurrent determination unit 48 outputs a predetermined command signal to the drive signal generation unit 44 to decelerate the motor M. As a result, the current flowing into the switching element can be reduced, and the driving of the motor M can be maintained while the temperature of the switching element is lowered.

<< Fourth Embodiment >>
Compared with the third embodiment, the motor drive device 100C according to the fourth embodiment includes a motor winding temperature detector 50, a motor demagnetization protection threshold setting unit 45, a motor demagnetization protection overcurrent determination unit 46, and However, the other points are the same as in the third embodiment. Therefore, the said different part is demonstrated and description is abbreviate | omitted about the part which overlaps with 3rd Embodiment.

FIG. 10 is a system configuration diagram including a motor driving device.
The motor winding temperature detector (winding temperature detection means) 50 detects the winding temperature of the motor M and outputs it to the motor demagnetization temperature protection threshold setting unit 45 every moment.
The motor demagnetization temperature protection threshold setting unit 45 sets a demagnetization protection threshold according to the motor winding temperature input from the motor winding temperature detector 50, and outputs it to the motor demagnetization protection overcurrent determination unit 46.
The motor demagnetization protection overcurrent determination unit 46 stops the process of the drive signal generation unit 44 when the motor current exceeds the demagnetization protection threshold based on the motor current and the demagnetization protection threshold.
Note that the processes executed by the motor winding temperature detector 50, the motor demagnetization protection threshold setting unit 45, and the motor demagnetization protection overcurrent determination unit 46 are the same as those in the second embodiment, and thus detailed description thereof is omitted. To do.

Further, the processing of the inverter control means 40C is executed through a microcomputer. That is, a fine demagnetization protection threshold is set finely according to the temperature characteristics of the switching element and the temperature characteristics (low temperature demagnetization characteristics or high temperature demagnetization characteristics) of the permanent magnet included in the motor M, and the inverter circuit 11 is driven as necessary. Stop.
On the other hand, the processing of the element short-circuit protection means 12 is executed without a microcomputer. Thereby, the element short-circuit protection means 12 stops the drive of the inverter circuit 11 in several μsec after detecting that the motor current exceeds the element short-circuit protection threshold.

<Effect>
According to the motor drive device 100C according to the present embodiment, the process of the inverter control means 40C is executed using a microcomputer. Therefore, an appropriate element temperature protection threshold is set according to the temperature of the switching element input from the element temperature detector 60, and appropriate according to the temperature of the motor winding input from the motor winding temperature detector 50. A demagnetization protection threshold can be set. That is, the motor M can be driven with the maximum current while preventing the temperature destruction of the switching element and the demagnetization of the permanent magnet provided in the motor M.

Therefore, according to the motor drive device 100C according to the present embodiment, the performance of the switching element and the performance of the motor M can be fully utilized and the reliability can be improved.
Further, by performing the processing by the element short-circuit protection means 12 without using a microcomputer, the drive of the inverter circuit 11 can be stopped within a few μsec after the overcurrent is detected. Thereby, it is possible to reliably prevent the switching element included in the inverter circuit 11 from being destroyed by an overcurrent.

≪Modification≫
As mentioned above, although each embodiment demonstrated the motor drive device which concerns on this invention, the embodiment of this invention is not limited to these description, A various change etc. can be performed.
For example, in the third embodiment and the fourth embodiment described above, the element temperature detector 60 detects the temperature of the switching element, but the present invention is not limited to this. That is, in place of the element temperature detector 60 (see FIG. 7), power module temperature detecting means (not shown) for detecting the surface temperature of the power module 10 (see FIG. 7) is provided, and the temperature of the switching element is indirectly measured. It is good also as detecting to.

In this case, the correlation between the temperature of the switching element and the element temperature protection threshold value is substituted with the correlation between the surface temperature of the power module 10 including the inverter circuit 11 and the element temperature protection threshold value.
That is, the inverter control means 40 sets the element temperature protection threshold corresponding to the temperature input from the power module temperature detection means, and stops driving the switching element when the motor current exceeds the element temperature protection threshold. Let
As a result, even when the power module 10 is used, the temperature of the switching element can be reliably protected, the temperature detector (power module temperature detecting means) mounting structure and the signal line drawing structure are simplified, and the manufacturing cost is reduced. Can be reduced.

Further, in place of the element temperature detecting means (see FIG. 7), substrate temperature detecting means (not shown) for detecting the surface temperature of the substrate (not shown) on which the inverter circuit 11 is mounted is provided, and the switching element It is good also as detecting temperature indirectly.
In this case, the inverter control means 40 sets an element temperature protection threshold corresponding to the temperature input from the substrate temperature detection means, and stops driving the switching element when the motor current exceeds the element temperature protection threshold. Let
Accordingly, the temperature protection of the element can be surely performed even in the form using the substrate temperature detection means, the temperature detector mounting structure and the signal line drawing structure are simplified, and the manufacturing cost can be reduced.

Further, in place of the element temperature detector 60 (see FIG. 7), a radiating fin temperature detecting means (not shown) for detecting the temperature of the radiating fin (not shown) for cooling the inverter circuit 11 is provided. It is good also as detecting temperature indirectly.
In this case, the inverter control means 40 sets an element temperature protection threshold corresponding to the temperature input from the radiating fin temperature detection means, and drives the switching element when the motor current exceeds the element temperature protection threshold. Stop.

Moreover, although each said embodiment demonstrated the case where all the switching elements which the inverter circuit 11 has were IGBT, it is not restricted to this.
That is, at least one of the switching elements included in the inverter circuit 11 may be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and the correlation with the element temperature protection threshold may be set based on the temperature of the MOSFET. .
Incidentally, the MOSFET has a larger loss (that is, the amount of heat generated) than the IGBT when the current increases. In particular, a MOSFET having a super junction structure among the MOSFETs is highly efficient when the current value is small. However, if the current value is large, the loss tends to be large, so that a thermal runaway is likely to occur.

  Accordingly, the element temperature detector 60 detects the temperature of the MOSFET type switching element, and the element temperature protection threshold value setting unit 47 sets the element temperature protection threshold value corresponding to the temperature. As a result, temperature protection of the switching element (including prevention of thermal runaway of the MOSFET) can be surely performed, and efficient operation can be performed in normal times.

  In the second and fourth embodiments described above, the motor winding temperature detector 50 detects the winding temperature of the motor M. However, the present invention is not limited to this. That is, a compressor (not shown) driven by the motor M is provided, and an outer temperature for detecting the temperature of the outer shell (not shown) of the compressor instead of the motor winding temperature detector 50 (see FIG. 4). It is good also as detecting the winding temperature of the motor M indirectly by a detection means (not shown).

That is, the correlation between the winding temperature of the motor M and the demagnetization protection threshold is substituted with the correlation between the outer temperature of the compressor and the demagnetization protection threshold.
In this case, the inverter control unit 40 sets a demagnetization protection threshold corresponding to the temperature input from the outer temperature detection unit, and stops driving the switching element when the motor current exceeds the demagnetization protection threshold. Let

Thereby, since the motor demagnetization protection is performed based on the correlation between the outer temperature of the compressor and the motor demagnetization protection threshold, the demagnetization protection of the motor M can be appropriately performed. In addition, the temperature detector (outer temperature detection means) mounting structure and signal line lead-out structure can be simplified and the manufacturing cost can be reduced as compared with the case where the temperature detector is installed inside the high pressure compressor.
Therefore, it is possible to provide a fluid compression system that can appropriately prevent the demagnetization of the permanent magnet included in the motor M.

Further, instead of the above-described motor winding temperature detector 50 (see FIG. 4), discharge pipe temperature detecting means for detecting the temperature of the discharge pipe (not shown) of the compressor (not shown) driven by the motor M. It is good also as detecting indirectly the winding temperature of the motor M by (not shown).
In this case, the inverter control means 40 sets a demagnetization protection threshold corresponding to the temperature input from the discharge pipe temperature detection means, and drives the switching element when the motor current exceeds the demagnetization protection threshold. Stop.
As a result, the demagnetization protection of the motor M can be reliably performed, and the mounting structure of the temperature detector (discharge pipe temperature detecting means) and the signal line drawing structure are simplified, and the manufacturing cost can be reduced.

Further, the winding of the motor M is based on the outer temperature of the compressor input from the outer temperature detecting means (not shown) for detecting the outer temperature of the compressor and the current detection value input from the current detector 20. The line temperature may be estimated.
The winding temperature of the motor M is in a state higher than the outer temperature of the compressor due to heat generation (motor loss) accompanying the inflow of current. Therefore, how much the winding temperature of the motor M is higher than the outer shell temperature of the compressor is corrected using the detected current value input from the current detector 20 as a parameter.

In this case, the inverter control means 40 calculates the motor loss, which is the amount of heat generated in the motor M, based on the outer temperature input from the outer temperature detection means and the current value input from the current detector 20. The winding temperature of the motor M is estimated corresponding to the calculated motor loss. That is, the winding temperature of the motor M is corrected using the detected current value input from the current detector 20 as a parameter.
Further, the inverter control means 40 sets a demagnetization protection threshold corresponding to the estimated motor winding temperature, and stops driving of the switching element when the motor current exceeds the demagnetization protection threshold.
As a result, the winding temperature of the motor M can be accurately reproduced, the operable range of the motor M can be expanded, and the demagnetization protection of the motor M can be more reliably performed.

Further, based on the discharge pipe temperature of the compressor input from the discharge pipe temperature detection means (not shown) for detecting the discharge pipe temperature of the compressor and the current detection value input from the current detector 20, the motor The winding temperature of M may be estimated. In this case as well, the winding temperature of the motor M is corrected using the detected current value input from the current detector 20 as a parameter, as in the case described above.
In addition, since the process of the inverter control means 40 is the same as that of the above case, description is abbreviate | omitted.

Further, in each of the above-described embodiments and modifications, the motor M may be a DC brushless motor using a permanent magnet. The compressor (not shown) can be a high-pressure chamber compressor driven by the DC brushless motor.
Thus, by using a DC brushless motor as the motor M for the compressor, high energy efficiency can be realized. In addition, it is possible to provide a fluid compression system that can appropriately protect the switching element of the inverter circuit 11 and reliably prevent demagnetization of the motor M.

Further, as the compressor (not shown), a low-pressure chamber compressor driven by a DC brushless motor is used, and an outdoor unit (not shown) is used instead of the motor winding temperature detector 50 (see FIG. 4). It is good also as using the frost formation detection means (not shown) installed in the indoor temperature detection means (not shown) installed in an indoor unit (not shown).
In this case, during the heating operation, the winding temperature of the motor M is indirectly detected by the frosting detection means installed in the outdoor unit. Then, the inverter control means 40 sets a demagnetization protection threshold corresponding to the temperature input from the frost formation detection means, and stops driving the switching element when the motor current exceeds the demagnetization protection threshold.

  On the other hand, during the cooling operation, the winding temperature of the motor M is indirectly detected by the indoor temperature detection means installed in the indoor unit. Then, the inverter control unit 40 sets a demagnetization protection threshold corresponding to the temperature input from the room temperature detection unit, and stops driving of the switching element when the motor current exceeds the demagnetization protection threshold.

That is, the inverter control means 40 uses the thermal correlation between the winding temperature of the motor M and the frosting temperature of the heat exchanger, or the thermal correlation between the winding temperature of the motor M and the room temperature. Then, the winding temperature is estimated.
As a result, demagnetization of the motor M can be reliably prevented, and the temperature detector (frosting detection means and indoor temperature detection means) mounting structure and signal line drawing structure are simplified, and the manufacturing cost can be reduced.

An air conditioner (not shown) may include the fluid compression system described above. In this case, the compressor provided with the motor M described above is installed in the outdoor unit.
Thereby, the protection of the switching element and the demagnetization protection of the motor M can be reliably performed, and a highly reliable air conditioner can be provided. Moreover, even when the air conditioner is required to have a large capacity in a low-temperature or high-temperature environment with a large air-conditioning load, the air-conditioning apparatus can maximize its air-conditioning capacity.

  Further, in each of the embodiments described above, the case where a permanent magnet type synchronous motor is used as the motor M has been described, but the present invention is not limited to this. That is, the above embodiments can be similarly applied to other synchronous motors such as a winding synchronous motor and a reluctance motor.

In each of the above-described embodiments, the AC voltage input from the AC power supply 200 is converted into a DC voltage by the converter circuit 300, and further converted into a predetermined AC voltage by driving the switching element of the inverter circuit 11. However, the present invention is not limited to this. For example, a DC voltage may be input to the inverter circuit 11 from a storage battery (DC power supply: not shown).
Further, the DC voltage may be actively controlled using an active circuit (not shown).

100, 100A, 100B, 100C Motor drive device 10 Power module 11 Inverter circuit 12 Element short circuit protection means 13 Inverter drive circuit 20 Current detector (current detection means)
30 Amplifier 40, 40A, 40B, 40C Inverter control means (control means)
41 Motor current reproduction unit 42 Speed command unit 43 Overcurrent determination unit (control means)
44 Drive signal generator (control means)
45 Motor demagnetization protection threshold setting unit (control means)
46 Motor demagnetization protection overcurrent judgment part (control means)
47 element temperature protection threshold setting unit (control means)
48 element temperature protection overcurrent judgment part (control means)
50 Motor winding temperature detector (winding temperature detection means)
60 element temperature detector (element temperature detection means)
200 AC power supply 300 Converter circuit M Motor

Claims (19)

An inverter circuit that has a switching element and converts a DC voltage input from a DC power source into an AC voltage; and a current detection unit that detects a DC current supplied to the inverter circuit, and according to the conversion, A motor driving device that drives a motor with AC power output from an inverter circuit,
Control means for controlling on / off of the switching element;
When the current value input from the current detection means exceeds a short-circuit protection threshold for preventing a short circuit in the inverter circuit, comprising an element short-circuit protection means for stopping the driving of the switching element,
The control means estimates a motor current flowing into the motor from a current value input from the current detection means, and the motor current is other related to temperature protection of the switching element and / or demagnetization protection of the motor. Executing a process of stopping the driving of the switching element when the current threshold is exceeded,
The current value detected by the current detection means is input to the element short-circuit protection means, and is also input to a microcomputer that performs arithmetic processing related to the control means,
Processing of the element short-circuit protection means is performed without involvement of the microcomputer,
Motor driving apparatus characterized by processing of the control unit is performed by interposing the microcomputer. A winding temperature detecting means for directly or indirectly detecting the winding temperature of the motor;
The other current threshold value includes a demagnetization protection threshold value set based on a demagnetization characteristic of a magnet included in the motor,
The temperature characteristic of the demagnetization protection threshold has a temperature region in which the short circuit protection threshold is larger than the demagnetization protection threshold,
The control means sets the demagnetization protection threshold corresponding to the winding temperature input from the winding temperature detection means, and drives the switching element when the motor current exceeds the demagnetization protection threshold. The motor driving device according to claim 1, wherein the motor driving device is stopped. Comprising element temperature detecting means for directly or indirectly detecting the temperature of the switching element;
The other current threshold includes an element temperature protection threshold set based on an element characteristic of the switching element,
The temperature characteristic of the element temperature protection threshold has a temperature region in which the short circuit protection threshold is larger than the element temperature protection threshold,
The control means sets the element temperature protection threshold corresponding to the temperature of the switching element input from the element temperature detection means, and when the motor current exceeds the element temperature protection threshold, The motor drive device according to claim 1, wherein the drive is stopped. Winding temperature detection means for directly or indirectly detecting the winding temperature of the motor, and element temperature detection means for directly or indirectly detecting the temperature of the switching element,
The other current threshold includes a demagnetization protection threshold set based on a demagnetization characteristic of a magnet included in the motor, and an element temperature protection threshold set based on an element characteristic of the switching element,
The temperature characteristic of the demagnetization protection threshold has a temperature region in which the short circuit protection threshold is larger than the demagnetization protection threshold,
The temperature characteristic of the element temperature protection threshold has a temperature region in which the short circuit protection threshold is larger than the element temperature protection threshold,
The control means sets the demagnetization protection threshold corresponding to the winding temperature input from the winding temperature detection means, and corresponds to the temperature of the switching element input from the element temperature detection means. The device temperature protection threshold is set, and the driving of the switching device is stopped when the motor current exceeds at least one of the demagnetization protection threshold and the device temperature protection threshold. The motor drive device described in 1. The magnet of the motor has a demagnetization characteristic in which the demagnetization current value decreases as the temperature of the magnet decreases.
The control means sets the demagnetization protection threshold to be smaller as the winding temperature input from the winding temperature detection means becomes lower based on the demagnetization characteristics of the magnet. The motor drive device according to claim 2 or 4. The motor driving apparatus according to claim 5, wherein the magnet included in the motor is a ferrite magnet. The magnet of the motor has a demagnetization characteristic in which the demagnetization current value decreases as the temperature of the magnet increases.
The control means sets the demagnetization protection threshold to be smaller as the winding temperature input from the winding temperature detection means becomes higher, based on the demagnetization characteristics of the magnet. The motor drive device according to claim 2 or 4. The motor driving apparatus according to claim 7, wherein the magnet included in the motor is a rare earth magnet. The element temperature detecting means for indirectly detecting the temperature of the switching element is a power module temperature detecting means for detecting a surface temperature of a power module including the inverter circuit,
The control means sets the element temperature protection threshold value corresponding to the temperature input from the power module temperature detection means, and stops driving the switching element when the motor current exceeds the element temperature protection threshold value. The motor driving apparatus according to claim 3 or 4, wherein: The element temperature detecting means for indirectly detecting the temperature of the switching element is a substrate temperature detecting means for detecting a surface temperature of a substrate on which the inverter circuit is mounted,
The control means sets the element temperature protection threshold corresponding to the temperature input from the substrate temperature detection means, and stops driving the switching element when the motor current exceeds the element temperature protection threshold. The motor driving device according to claim 3 or 4, wherein The element temperature detection means for indirectly detecting the temperature of the switching element is a radiation fin temperature detection means for detecting the temperature of the radiation fin for cooling the inverter circuit,
The control means sets the element temperature protection threshold corresponding to the temperature input from the radiating fin temperature detection means, and stops driving the switching element when the motor current exceeds the element temperature protection threshold. The motor driving apparatus according to claim 3 or 4, wherein: At least one of the switching elements of the inverter circuit is a MOSFET,
The element temperature detection means detects the temperature of the MOSFET and outputs it to the control means,
5. The motor driving apparatus according to claim 3, wherein the control unit sets the element temperature protection threshold value corresponding to the temperature of the MOSFET input from the element temperature detection unit. The motor drive device according to claim 2 or claim 4,
A compressor driven by the motor,
The winding temperature detection means for indirectly detecting the winding temperature of the motor is an outer temperature detection means for detecting the outer temperature of the compressor,
The control unit sets the demagnetization protection threshold corresponding to the temperature input from the outer temperature detection unit, and stops driving the switching element when the motor current exceeds the demagnetization protection threshold. A fluid compression system characterized by the above. The motor drive device according to claim 2 or claim 4,
A compressor driven by the motor,
The winding temperature detecting means for indirectly detecting the winding temperature of the motor is a discharge pipe temperature detecting means for detecting a discharge pipe temperature of the compressor,
The control means sets the demagnetization protection threshold corresponding to the temperature input from the discharge pipe temperature detection means, and stops driving the switching element when the motor current exceeds the demagnetization protection threshold. A fluid compression system. The motor drive device according to claim 2 or claim 4,
A compressor driven by the motor,
The winding temperature detecting means for indirectly detecting the winding temperature of the motor includes outer temperature detecting means for detecting an outer temperature of the compressor, and the current for detecting a direct current supplied to the inverter circuit. Detection means,
The control means includes
Based on the temperature input from the outer temperature detection means and the current value input from the current detection means, a motor loss that is the amount of heat generated in the motor is calculated.
Estimating the winding temperature of the motor corresponding to the calculated motor loss,
Set the demagnetization protection threshold corresponding to the estimated winding temperature,
When the motor current exceeds the demagnetization protection threshold, driving of the switching element is stopped. The motor drive device according to claim 2 or claim 4,
A compressor driven by the motor,
The winding temperature detecting means for indirectly detecting the winding temperature of the motor detects a discharge pipe temperature detecting means for detecting a discharge pipe temperature of the compressor, and a direct current supplied to the inverter circuit. The current detection means;
The control means includes
Based on the temperature input from the discharge pipe temperature detection means and the current value input from the current detection means, a motor loss that is the amount of heat generated in the motor is calculated,
Estimating the winding temperature of the motor corresponding to the calculated motor loss,
Set the demagnetization protection threshold corresponding to the estimated winding temperature,
When the motor current exceeds the demagnetization protection threshold, driving of the switching element is stopped. The motor is a DC brushless motor using a permanent magnet,
The fluid compression system according to any one of claims 13 to 16, wherein the compressor is a high-pressure chamber compressor driven by the DC brushless motor. The motor drive device according to claim 2 or claim 4,
A low-pressure chamber compressor driven by the motor,
The motor is a DC brushless motor using a permanent magnet,
During heating operation, indirectly detect the winding temperature of the motor by frost detection means installed in the outdoor unit,
During cooling operation, the winding temperature of the motor is indirectly detected by the indoor temperature detection means installed in the indoor unit,
The control means includes
The demagnetization protection threshold is set corresponding to the temperature input from the frost detection means or the room temperature detection means, and when the motor current exceeds the demagnetization protection threshold, driving of the switching element is stopped. A fluid compression system. An air conditioner comprising the fluid compression system according to any one of claims 13 to 18.

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