JP3024553B2 - Abnormality detection device for power conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detection apparatus for a power conversion circuit, and more particularly to a power conversion circuit which stops supplying power when an inverter output current value reaches a predetermined overcurrent value. In addition, the present invention relates to a measure for shortening an overcurrent conduction time when stopping the power supply.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Publication No.
There is known an air conditioner provided with a compressor whose operating frequency is made variable by a power conversion circuit provided with an inverter circuit, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-15095. Then, this type of power conversion circuit performs full-wave rectification of the three-phase alternating current from the power supply, temporarily converts it to direct current, smoothes it, converts this direct current to alternating current of a desired frequency, Is applied to the compressor motor.

In this type of circuit, when the inverter output current value rises abnormally and exceeds a preset overcurrent value for a predetermined time, power supply to the compressor motor is temporarily stopped. The compressor is stopped to protect the compressor motor.

More specifically, the stopping operation is performed when the supply frequency of the compressor motor is in a low frequency range (for example, a frequency of 20 Hz or less) at the time of starting the compressor or the like. Action)
There is a stop operation (hereinafter, this operation is referred to as an electronic thermal operation) performed when the supply frequency of the compressor motor is higher than the low frequency range (frequency 20 Hz or higher).

[0005] Each operation will be described in detail. First, in the stall operation, the supply frequency of the compressor motor is set to two.
At 0 Hz or less, when a state in which the inverter output current value exceeds a predetermined stall determination current value (for example, 33 A) is integrated and a predetermined stall determination time (for example, an integration time of 5 sec) elapses, the power to the compressor motor is reduced. Stop supply. On the other hand, in the electronic thermal operation, when the supply frequency of the compressor motor is 20 Hz or more and the inverter output current value is a predetermined electronic thermal determination current value (for example, 33 A as described above).
When the state exceeding the predetermined time exceeds a predetermined electronic thermal determination time (for example, 30 seconds), the power supply to the compressor motor is stopped. That is, in a situation where an overcurrent is flowing when the compressor is started (low frequency range), the compressor may be locked for some reason. In this case, the power supply is performed in a short time. The judgment time is set short so that it can be stopped. On the other hand, during steady-state operation with a relatively high frequency, a large current may temporarily flow due to load fluctuations, etc., so the determination time should be set relatively long so as not to stop the compressor each time. I have.

[0006]

However, in the conventional motor protection operation, since the stall operation and the electronic thermal operation are switched according to the supply frequency, the following problems occur. Become.

That is, when the inverter output current value exceeds the stall judgment current value (33 A) when the supply frequency of the compressor motor is in the low frequency range (20 Hz or less), the state is the stall judgment time (5 sec). If the supply frequency of the compressor motor shifts to a high frequency range (20 Hz or more) before the stall operation is reached, the stall operation is canceled and the operation shifts to the electronic thermal operation instead. That is, for example, immediately after the state where the supply frequency is 20 Hz or less and the inverter output current value is 33 A or more is integrated for 4 seconds, if the supply frequency rises to 20 Hz or more, the operation shifts from the stall operation to the electronic thermal operation. Even if the state where the output current value is 33 A or more continues, the power supply is not stopped by the stall operation. In this electronic thermal operation, the power supply to the compressor motor is stopped only when the state in which the inverter output current value is 33 A or more continues for 30 seconds after the supply frequency becomes 20 Hz or more. In other words, if the operation does not shift from the stall operation to the electronic thermal operation, the power supply can be stopped after 5 seconds (integrated time) from the time when the inverter output current value becomes 33 A or more,
Since the operation has shifted from the stall operation to the electronic thermal operation, power supply cannot be stopped until 34 seconds have elapsed since the inverter output current value became 33 A or more. For this reason, there is a possibility that the time for supplying the overcurrent to the compressor motor becomes longer and the protection thereof cannot be sufficiently achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and it has been found that the overcurrent supply time to the compressor motor is long while maintaining the stall operation and the electronic thermal operation in good condition. An object of the present invention is to sufficiently protect a compressor motor by avoiding excessive bending.

[0009]

[Means for Solving the Problems]

-Summary of the invention- The present invention converts a power supplied from a power supply (PS) into a predetermined control power through an inverter circuit (23) and converts the power into a load (C).
M). In addition, load (C
The overcurrent detection operation is performed depending on whether the supply frequency supplied to M) is higher or lower than a predetermined frequency set in advance. And, when the current value of the load (CM) reaches a predetermined overcurrent value when the frequency is in the low frequency range, regardless of the fluctuation of the supply frequency,
When the overcurrent state reaches a predetermined determination time, power supply to the load (CM) is stopped.

-Specific Items of the Invention- Specifically, as shown in FIG. 1, means taken by the invention according to claim 1 is a power supply that is first supplied from a power supply (PS) to a load (CM). And an inverter circuit (23) for controlling the operation. In addition, the inverter circuit (23) keeps the supply frequency (F) supplied from the inverter circuit (23) to the load (CM) in a frequency range higher than a predetermined frequency, and
When the current value (I) of the load (CM) supplied from (23) is
A first detection means (43) for generating an abnormal signal when the overcurrent state reaching the overcurrent value (Ith) continues for the first determination time or longer is provided. Then, the load (C
When the supply frequency (F) supplied to the load (CM) is lower than the predetermined frequency, the current (I) of the load (CM) reaches the predetermined second overcurrent value (Is). When the current state is reached,
Regardless of the variation of the supply frequency (F), a second detection means (44) for generating an abnormal signal when the overcurrent state reaches a predetermined second determination time is provided, and the first detection means (43) or the second detection means is provided. (2) When an abnormal signal is received from the detecting means (44), a stop means (45) for stopping power supply to the load (CM) is provided.

The means adopted by the second aspect of the present invention is the same as the first aspect, wherein the first detecting means (4
3) is that an abnormal signal is issued when the overcurrent state in which the current value (I) of the load (CM) reaches the first overcurrent value (Ith) continuously reaches the first determination time, while the second The detection means (44) is a load (CM)
The overcurrent state in which the current value (I) reaches the second overcurrent value (Is) is integrated, and an abnormal signal is issued when the integrated time reaches the second determination time.

[0012] Further, according to a third aspect of the present invention, in the first aspect, the load (CM) is a motor of a compressor provided in the air conditioner.

According to the present invention, first, in the present invention, the inverter circuit (23) controls the power from the power supply (PS) to control the load (C).
M). In this state, in a state where the supply frequency supplied from the inverter circuit (23) to the load (CM) holds a frequency range higher than a predetermined frequency set in advance, the current value of the load (CM) ( When the overcurrent state in which (I) has reached the predetermined first overcurrent value (Ith) continues for the first determination time or longer, the first detection means (43) issues an abnormal signal. on the other hand,
When the supply frequency (F) supplied to the load (CM) from the inverter circuit (23) is in a frequency range lower than the predetermined frequency, the current value (I) of the load (CM) is changed to a predetermined second overcurrent. Value (I
s), the second detection means (44)
Irrespective of the fluctuation of the supply frequency (F), when this overcurrent state reaches a predetermined second judgment time, an abnormal signal is issued. And
When the stopping means (45) receives an abnormal signal from any of the detecting means (43, 44), the power supply to the load (CM) is stopped.

Therefore, when the supply frequency (F) is in a frequency range lower than the predetermined frequency, the current value (I) of the load (CM)
When the current reaches the second overcurrent value (Is), the current value (I) reaches the second overcurrent value (Is) even if the supply frequency (F) subsequently increases. The power supply stop operation for the load (CM) is performed under the determination condition of whether or not the state has reached the second determination time.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 2, (10) is an induction motor (C) of a compressor provided in the outdoor unit of the air conditioner.
M), comprising a power conversion circuit (20) and a power control circuit (30), and an induction motor (C) using a control power as a load from a power supply (PS) via the power conversion circuit (20).
M).

The power conversion circuit (20) converts three-phase AC power supplied from a power supply (PS) into controlled three-phase AC power, and includes a rectifier circuit (21) and a smoothing circuit (2).
2) and an inverter circuit (23). And
The rectifier circuit (21) includes six diodes (d1, d1,
…) And a power supply (P
A diode module connected to S) that performs full-wave rectification on AC from the power supply (PS).

The smoothing circuit (22) is for smoothing the direct current that has been full-wave rectified by the rectifier circuit (21), and is provided with a reactor (2L) and a capacitor circuit (2C) having a smoothing capacitor (2C). 2a) and a resistor circuit (2b) having a discharge resistor (2R) are connected to a power supply line (2P, 2P).
N). The smoothing circuit (22) has a DC section current, that is, an induction motor (C
A current transformer (CT), which is a current detector for detecting a motor current that is a current M), is provided on the power supply line (2N).

The inverter circuit (23) includes a transistor having six power transistors (Tr, Tr,...).
A smoothing circuit (22) is a transistor module that converts a smoothed direct current into an alternating current, and is connected to an induction motor (CM) to supply three-phase AC control power to the induction motor (CM). I have. The power transistors (Tr, Tr,...) Are connected with a free-wheeling diode (d2, d2,...) Between the emitter and the collector, and the power transistors (Tr, Tr,. ) Is turned ON / OFF by the drive signal.

The power control circuit (30) is provided with a drive circuit (31) and a CPU (40) while receiving a current signal from a current transformer (CT). The drive circuit (31) controls the power transistors (Tr, Tr,...) So that the power transistors (Tr, Tr,...) Perform PWM modulation (pulse width modulation) on the DC section voltage smoothed by the smoothing circuit (22).
To output a drive signal. An air conditioning load signal such as an indoor temperature is input to the CPU (40).
Speed control means (41) and optimum control means (42) are provided.

The speed control means (41) receives an air conditioning load signal such as an indoor temperature and derives a supply frequency of an induction motor (CM) which is an operating frequency of the compressor in accordance with the air conditioning load signal. Then, a control signal is output to the drive circuit (31) so as to have the supply frequency.

That is, the speed control means (41) drives and controls the inverter circuit (23) such that the supply frequency and the supply voltage of the induction motor (CM) change based on a preset reference voltage frequency characteristic. A control signal for controlling the supply frequency of the induction motor (CM) to control the induction motor (CM) at a variable speed is output to the drive circuit (31). Then, the drive circuit (31) outputs the drive signal to the inverter circuit (23) of the power conversion circuit (20) based on the control signal.

The optimum control means (42) drives an adjustment signal for adjusting the supply voltage of the induction motor (CM) so as to make the supply voltage small so as to minimize the motor current by slightly changing the supply voltage by a predetermined amount of change. Output to the circuit (31). Then, the drive circuit (31) outputs the drive signal to the inverter circuit (23) of the power conversion circuit (20) based on the adjustment signal.

Further, the CPU (40) is provided with a first detecting means (43), a second detecting means (44) and a stopping means (45) as features of the present invention. Hereinafter, each means will be described.

The first detecting means (43) includes an inverter circuit (23)
The supply frequency (F) supplied from the inverter motor (CM) to the induction motor (CM) maintains a frequency range higher than a predetermined frequency (for example, 20 Hz), and the induction motor (CM) supplied from the inverter circuit (23). The overcurrent state in which the current value (hereinafter simply referred to as the motor current value) (I) of the CM) reaches the electronic thermal determination current value (Ith) as the predetermined first overcurrent value continues for the first determination time. When an electronic thermal determination time (e.g., 30 seconds) continues for more than one time, an abnormal signal is issued. That is, the first detection means (43)
When the motor current value (I) reaches the electronic thermal judgment current value (Ith) when (F) is 20 Hz or more, counting starts, and this motor current value (I) becomes the electronic thermal judgment current value (Ith).
th) The timer is provided with a first timer (T1) that continues counting when it is equal to or more than 30 seconds and that times up when the count reaches 30 seconds continuously. Emits a signal.

The second detecting means (44) includes an inverter circuit (23)
When the supply frequency (F) supplied from the motor to the induction motor (CM) is in a frequency range lower than the above-mentioned predetermined frequency, the motor current value (I) becomes the stall determination current value (Is ), An abnormal signal is generated when the overcurrent state is integrated and the stall determination time as the second determination time is reached, regardless of the fluctuation of the supply frequency (F). ing. That is, the second detection means (4
4) is “1” when the motor current value (I) reaches the stall judgment current value (Is) when the supply frequency (F) is 20 Hz or less.
If the motor current value (I) is equal to or greater than the stall detection current value (Is), the count starts with the setting of the stall detection flag (Fs) and the stall detection flag (Fs). And a second timer (T2) which counts up when the count reaches 5 sec., And issues an abnormal signal with the time up of the second timer (T2).

When the stop means (45) receives an abnormal signal from the first detection means (43) or the second detection means (44), the stop means (45) stops power supply to the induction motor (CM).
The operation of the power conversion circuit (20) is stopped.

-Control operation of induction motor (CM)-Next, the control operation of the above-described induction motor (CM) will be described.

First, when an operation command such as a cooling operation is output from a remote controller (not shown) in a state where the power supply (PS) is turned on and the switching circuit (11) is turned on, the microcomputer (40) receives the operation command. Speed control means (41)
Outputs a control signal. This control signal is sent to the drive circuit (31)
Outputs the drive signal to the inverter circuit (23),
The power transistors (Tr, Tr, ...) are turned ON / OFF.

On the other hand, the three-phase AC power from the power supply (PS) is full-wave rectified by the rectifier circuit (21), converted to DC, and then smoothed by the smoothing circuit (22).
Output to the inverter circuit (23). Then, the six power transistors (Tr, Tr, Tr) of the inverter circuit (23).
..) Converts DC to AC and PWM modulates to apply a predetermined supply voltage to the induction motor (CM).

The microcomputer (40) receives an air-conditioning load signal such as room temperature and the like, and controls the speed control means (41).
Derives the supply frequency of the induction motor (CM), which is the operating frequency of the compressor, in response to the air conditioning load signal,
A control signal is output to the drive circuit (31) so as to have this supply frequency. That is, the speed control means (41) controls the inverter circuit (23) so that the supply frequency and the supply voltage of the induction motor (CM) change based on the preset reference voltage frequency characteristic. And the drive circuit (31) outputs a drive signal to the inverter circuit (23) based on the control signal. As a result, the induction motor (CM) rotates corresponding to the air-conditioning load.

During the rotation of the induction motor (CM), the optimal control means (42) slightly changes the supply voltage of the induction motor (CM) by a predetermined amount of fluctuation so that the motor current is minimized. And outputs an adjustment signal to the drive circuit (31). Then, the drive circuit (31) outputs a drive signal to the inverter circuit (23) based on the adjustment signal so that the induction motor (CM) rotates at the most efficient minimum current value.

-Current Abnormality Processing Operation- Next, as an operation characteristic of the present embodiment, a current abnormality processing operation when the inverter output current value reaches a predetermined overcurrent value will be described with reference to the flowchart of FIG. .

First, in step ST1, the induction motor (C
It is determined whether the supply frequency (F) of M) is equal to or lower than 20 Hz or the stall detection flag (fs) is set to “1”. If at least one of these two conditions is satisfied, the process proceeds to step ST2 (when the operation of the compressor is started, the stall detection flag (Fs) is “0” and the supply frequency of the induction motor (CM) is Since (F) is equal to or lower than 20 Hz, the process moves to step ST2 when this frequency condition is satisfied.)

Then, in this step ST2, it is determined whether or not the motor current value (I) exceeds the stall determination current value (Is). If this motor current value (I) exceeds the stall determination current value (Is), the process proceeds to step ST
At 3, it is determined whether or not the operation of the second timer (T2) has been started (the second timer (T2) is in the non-operating state when the operation of the compressor is started), and the second timer (T2) is determined. If NO has not started yet, the second timer (T2) is operated to start counting in step ST4, and the stall detection flag (fs) is set to "1" in step ST5.

On the other hand, in step ST2, the motor current value (I)
If NO is equal to or less than the stall determination current value (Is), it is determined in step ST6 whether or not the second timer (T2) is counting.
In ST7, it is determined whether or not the stall detection flag (fs) is set to "1". Here, if the stall detection flag (fs) is set to "1", the process proceeds to step ST8, where the count of the second timer (T2) is stopped, and in step ST9, the stall detection flag is set.
(fs) is reset to “0”.

As described above, in the situation where the count start or count stop operation of the second timer (T2) is being performed, in step ST2, the motor current value (I) exceeds the stall determination current value (Is). In this case, the process proceeds from step ST3 to step ST10, and it is determined whether or not the stall detection flag (fs) is set to “1”. And
Stall detection flag (fs) is set to "1"
If YES, the second timer (T2) in step ST11
It is determined whether the integration time of has reached 5 sec. That is, it is determined whether or not the power supply stop condition due to the stall operation is satisfied.
At 12, the power supply to the induction motor (CM) is stopped to protect the induction motor (CM).

In step ST10, if the stall detection flag (fs) is "0" (NO), that is, after the stall detection flag (fs) is reset to "0" in step ST9, the motor current value (I) is the stall judgment current value
If (Is) or more, the process proceeds to step ST13 where the second timer (T2) starts counting and
In ST14, the stall detection flag (fs) is set to "1".

Such an operation is continuously performed until the determination in step ST1 is NO. That is, once the supply current (F) of the induction motor (CM) is 20 Hz or less and the motor current value (I) exceeds the stall determination current value (Is), thereafter, the induction motor (CM) ) Is not limited to the supply frequency (F) of the induction motor (CM) unless the condition that the inverter output current value (I) is equal to or less than the stall judgment current value (Is) is not less than 20 Hz. If the motor current value (I) exceeds the stall determination current value (Is) (even if the frequency becomes 20 Hz or more), the second timer (T2) is counted, and the count integration time becomes 5 seconds. When it reaches, an operation such as stopping power supply to the compressor motor (CM) is performed. In other words, once the motor current value (I) exceeds the stall determination current value (Is) and the stall detection flag is set to “1”, the induction motor (C
Even if the supply frequency (F) of M) becomes 20 Hz or more, the stall operation is performed according to the stall determination condition without moving to the electronic thermal operation.

When the determination in step ST1 is NO, that is, when the supply frequency (F) of the induction motor (CM) is 2
If the frequency is 0 Hz or more and the stall detection flag (fs) is “0”, the process proceeds to the electronic thermal operation in step ST15 and subsequent steps. That is, in step ST15, the motor current value
It is determined whether or not (I) exceeds the electronic thermal determination current value (Ith). If the motor current value (I) exceeds the electronic thermal determination current value (Ith) in the case of YES,
In step ST16, the operation of the first timer (T1) is started. In step ST17, if this state continues for 30 seconds, in step ST18 the induction motor (CM) is started.
Power supply to is stopped. On the other hand, in step ST15, the motor current value (I) is changed to the electronic thermal determination current value (It
h) If the following occurs, the first timer (T1) is reset.

Because of such an operation, in the present embodiment, the supply frequency increases immediately before the stall determination condition is satisfied, as in the related art, and the operation shifts from the stall operation to the electronic thermal operation. In addition, it is possible to avoid a situation in which the time when the operation shifts to the power supply stop operation is delayed, and the time for applying the overcurrent to the induction motor (CM) is lengthened. For this reason, while maintaining the individual operations of the stall operation and the electronic thermal operation satisfactorily, it is possible to protect the induction motor (CM) by preventing the overcurrent application time to the induction motor (CM) from becoming too long. Reliability can be improved.

In this embodiment, the induction motor (CM) of the compressor of the air conditioner has been described.
According to the present invention, various types of induction motors (CM)
Can be applied to

Although the inverter circuit (23) in the present embodiment uses six power transistors (Tr, Tr,...), The present invention uses six IGBTs (Insulated Gate).
Bipolar Transistor) may be used.

[0044]

Therefore, according to the present invention, the following effects are exhibited. According to the first aspect of the present invention, a power conversion circuit having different overcurrent determination conditions according to a supply frequency supplied from an inverter circuit to a load is provided.
When the supply frequency is in a relatively low frequency range and the current value of the load becomes an overcurrent state, power supply to the load is stopped when the overcurrent state reaches a predetermined determination time regardless of the fluctuation of the supply frequency. As a result, as in the conventional case, the supply frequency rises immediately before the determination condition in the low frequency range is satisfied, so that the operation shifts to the determination operation in the high frequency range and the time to shift to the power supply stop operation is delayed. As a result, it is possible to avoid a situation in which the time for supplying the overcurrent to the load becomes longer. For this reason, it is possible to prevent the time for applying the overcurrent to the load from becoming too long, and to improve the reliability of protection of the load.

According to the second aspect of the present invention, the determination condition by the first detection means is that the overcurrent state has continuously reached the determination time, and the determination condition by the second detection means is that the overcurrent state is Since it has been determined that the judgment time has been reached by integrating
The operation of each means can be embodied, and the practicality of the device can be improved.

According to the third aspect of the present invention, since the load is a motor of a compressor provided in the air conditioner,
The reliability of the air-conditioning operation can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a control circuit diagram of the induction motor.

FIG. 3 is a flowchart illustrating a current abnormality processing operation.

[Explanation of symbols]

 20 Power conversion circuit 23 Inverter circuit 43 First detecting means 44 Second detecting means 45 Third detecting means PS power supply CM induction motor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-31194 (JP, A) JP-A-5-300852 (JP, A) JP-A-1-308195 (JP, A) JP-A-59-1984 54789 (JP, A) JP-A-8-9684 (JP, A) Japanese Utility Model Laid-Open No. 61-159841 (JP, U) Japanese Utility Model Application Laid-Open No. 6-9399 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) H02P ^7/ 628-7/632 H02M 7/48 F24F 11/02 102 F25B 1/00 361-371 F04B 49/10 331 H02H 7/122

Claims (3)

(57) [Claims] An inverter circuit (23) for controlling power supplied from a power supply (PS) to a load (CM), and a supply frequency (F) supplied from the inverter circuit (23) to the load (CM). ) Holds a frequency range higher than a predetermined frequency set in advance, and the current value (I) of the load (CM) supplied from the inverter circuit (23) is a predetermined first overcurrent value (It).
h) when the overcurrent state continues for more than the first determination time, the first detection means (43) for generating an abnormal signal, and the supply frequency (F) supplied from the inverter circuit (23) to the load (CM). ) Is in a frequency range lower than the predetermined frequency, the current value (I) of the load (CM) becomes the predetermined second overcurrent value.
When the overcurrent state reaches (Is), regardless of the fluctuation of the supply frequency (F), a second detection means (44) that issues an abnormal signal when the overcurrent state reaches a predetermined second determination time, Power conversion circuit, comprising: a stop means (45) for stopping power supply to a load (CM) when an abnormal signal is received from the first detection means (43) or the second detection means (44). Abnormality detection device. 2. The abnormality detection device for a power conversion circuit according to claim 1, wherein the first detection means (43) has reached a state in which the current value (I) of the load (CM) has reached the first overcurrent value (Ith). An abnormal signal is issued when the overcurrent state continuously reaches the first determination time, while the second detecting means (44) detects that the current value (I) of the load (CM) is equal to the second overcurrent value (Is). An abnormality detection device for a power conversion circuit, characterized in that an overcurrent state that has reached a maximum value is accumulated, and an abnormality signal is issued when the accumulation time reaches a second determination time. 3. The abnormality detection device for a power conversion circuit according to claim 1, wherein the load (CM) is a motor of a compressor provided in the air conditioner.