JP4906836B2 - Electric motor drive device, refrigeration air conditioner, and electric motor drive method - Google Patents

Description

  The present invention relates to an electric motor driving device used for driving an electric motor such as a compressor of a refrigeration air conditioner, and the electric motor driving for driving an electric motor having an electric motor winding (stator winding) as an independent winding. It relates to devices and the like.

  As low-cost and high-performance variable voltage / variable frequency inverters are put into practical use, various application fields for variable speed motor driving have been developed. Among them, in a field where the static friction force of the driven machine is relatively large and a large starting torque (load) is required, an inverter circuit corresponding to a large capacity output is required. However, since it is disadvantageous in cost to use such an inverter circuit only to obtain torque at the time of starting, various methods for switching the motor winding specifications of the motor without increasing the output of the inverter circuit Has been proposed.

For example, in a device having a voltage source inverter circuit, there are two sets of three-phase bridge circuits (inverter circuits) composed of power semiconductor switching elements such as thyristors, transistors, etc. The terminals are directly connected to the positive terminal and the negative terminal of the DC voltage source, respectively. The other three-phase bridge circuit is connected to the positive terminal and the negative terminal of the DC voltage source via a switch such as a power semiconductor element or an electromagnetic contactor. And an ON / OFF signal for connecting each phase winding of the induction motor between corresponding phases of each three-phase bridge circuit and performing delta connection operation or equivalent star connection operation for the switching element of each three-phase bridge circuit And a device provided with means for giving a PWM control signal is disclosed (for example, see Patent Document 1).
Japanese Patent Publication No. 7-99959 (FIG. 1)

The conventional apparatus as described above can cope with induction motors because of the large number of switches required for switching, but it is difficult to control synchronous motors that require quick switching to maintain synchronization. It was difficult to realize. In addition, since the number of switches is large, it is difficult to cope with variations between elements at ON / OFF. In addition, the number of elements through which current flows during star connection operation is large, and depending on the operating conditions (motor power factor, modulation factor), the total switching element ON loss as a system increases, resulting in a problem that the inverter efficiency decreases. .
Furthermore, when one switching element in the three-phase bridge circuit connected to the positive electrode terminal and the negative electrode terminal of the DC voltage source through a switch such as a power semiconductor element or an electromagnetic contactor breaks down, or the motor and the three-phase bridge circuit If a disconnection occurs between the two, the operation cannot be performed only on the remaining three-phase bridge circuit side, so the operation guarantee restrictions as a system were large.

  Therefore, in the motor drive device for switching the motor winding specifications (connection state of the motor), the winding connection switching can be performed quickly and reliably so as to be compatible with the synchronous motor, the drive system can be highly efficient, and An object is to obtain an electric motor drive device or the like that has a relatively small influence even if there is a failure or the like.

The electric motor drive device according to the present invention is connected to the electric lead wire of the electric motor drawn out by cutting off the neutral point of the electric motor winding, and the operation for driving the electric motor by voltage application by PWM based on the first PWM signal The master-side inverter circuit that performs the operation and the slave-side inverter circuit that is connected to a separate lead line from the master-side inverter circuit and performs the operation for driving the motor based on the second PWM signal, and neutral point short-circuit switching One short-circuit switch used for the motor, and based on the switching signal, the star connection specification for driving the motor by the operation of only the master-side inverter circuit, or the motor by the cooperative operation of the master-side inverter circuit and the slave-side inverter circuit Switch the motor winding specification of the motor to one of the open winding specifications for driving operation Therefore, a short circuit that is connected to the lead line in parallel with the slave side inverter circuit, and a control means that transmits the first PWM signal and the second PWM signal to the master side inverter circuit and the slave side inverter circuit, and transmits the switching signal to the short circuit. Are provided.

  According to the electric motor drive device according to the present invention, it has a master side inverter circuit and a slave side inverter circuit, is connected to the lead wire of the electric motor, and can be driven by the star connection specification and the open winding specification, Furthermore, it has a short circuit, and in the star connection specification, all the switching elements of the slave side inverter circuit are turned off and opened, and each phase is electrically connected by the short circuit to turn on all the slave side inverter circuits. There is no need to short circuit. Therefore, it is possible to quickly switch the motor winding specifications, and it can be used not only for induction motors but also for synchronous motors. Further, since the number of switches is small, it is easy to deal with variations between elements at ON / OFF (relative management is easy), and the reliability of the system can be increased. In addition, since the number of switch elements in the short circuit can be reduced, the ON loss of the switching element can be made smaller than before depending on the operating conditions (motor power factor and modulation factor). Moreover, even if a switching element open failure of the slave side inverter circuit or a disconnection with the motor occurs, the operation of the master side inverter circuit can be continued, so that the reliability as a system can be increased. .

  Hereinafter, an electric motor drive device according to an embodiment of the present invention and a refrigeration air conditioner having the electric motor drive device will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an example of a system configuration centering on an electric motor drive apparatus according to Embodiment 1 of the present invention. The system shown in FIG. 1 is, for example, a CPU (Central Processing Unit) for controlling the connection state of the DC voltage source 1, the master-side inverter circuit 2 and the slave-side inverter circuit 3, the inverter circuits and the motor windings of the motor 6. The control means 41 comprised by the motor, the electric motor 6 which made the motor winding an independent winding, the current detection means 51-53 for detecting the electric current which flows into the electric motor 6, DC bus voltage (henceforth bus voltage) is detected The voltage detection means 54 and the motor winding specifications of the motor 6 are star connection specifications (when the motor 6 is driven by only one operation by the master-side inverter circuit 2; hereinafter referred to as single operation) or open winding Specifications (when the motor 6 is driven and operated by the cooperative operation of two inverters, the master side inverter circuit 2 and the slave side inverter circuit 3). Under constitute a shorted circuit 23 for switching on) of coordinated operation. Among these, the master side inverter circuit 2, the slave side inverter circuit 3, the current detection means 51 to 53, the voltage detection means 54, the control means 41, and the short circuit 23 constitute an electric motor drive device. In this embodiment, it is assumed that the electric motor driving device is mounted on one electronic substrate 31. Here, the electric motor drive device does not necessarily have to be mounted on one electronic substrate 31, and may be configured to be divided into blocks including one or a plurality of circuits, for example, and mounted on a plurality of substrates for each block.

  In this embodiment, the short circuit 23 includes a three-phase rectifier circuit 21, a short circuit switch 22, and a short circuit switch state switching circuit 24. The master-side inverter circuit 2 is a circuit having switching elements 7a to 7f and diodes 9a to 9f. An arm is formed by combining a switching element and a diode. Then, current detection elements 11a to 11c are inserted (connected) for overcurrent protection and motor control between the lower arm and the DC bus of each master-side inverter circuit 2 of the present embodiment. The slave-side inverter circuit 3 is also a circuit composed of switching elements 8a to 8f and diodes 10a to 10f. In the slave-side inverter circuit 3, a current detection element 12 is inserted (connected) for overcurrent protection between the DC bus path.

  The current detection means 51 to 53 are configured by an A / D converter, an amplifier, and the like. Here, in the current detection of the present embodiment, the both-end voltage obtained from the current detection elements 11 a to 11 c is converted into numerical data representing the voltage value, and a signal including the data is transmitted to the control means 41. Then, the control means 41 performs the conversion by converting the data (information) of the motor current based on the data included in the signal (however, it is not limited to this method). Further, the voltage detection means 54 of the present embodiment is constituted by a voltage dividing circuit composed of a resistor / capacitor, an A / D converter, an amplifier, and the like. The bus voltage is converted into numerical data, and a signal including the data is transmitted to the control means 41. The control means 41 performs processing based on data included in the signal.

  First, an electric motor drive operation method using PWM (Pulse Width Modulation) will be described. In the present embodiment, a case will be described in which the magnetic pole position sensor is not added and the control means 41 performs control for driving the electric motor 6 based on data (information) of the current flowing through the winding.

  In the motor drive device of FIG. 1, the control means 41 is controlled by the current detection elements 11a to 11c via the current detection means 51 to 53 regardless of whether the motor winding specification is in the star connection specification or the open winding specification. Thus, motor current data can be obtained. Also, bus voltage data can be obtained via the voltage detection means 54. An operation is performed based on these data to generate a PWM duty signal (hereinafter referred to as a PWM signal), and the master-side inverter circuit 2 and the slave-side inverter circuit 3 are operated to apply a voltage to the electric motor 6. Perform drive operation control.

  FIG. 2 is a diagram illustrating a flowchart for generating a PWM signal. Here, a process in which the control means 41 creates a PWM signal to be output to the master-side inverter circuit 2 and / or the slave-side inverter circuit 3 based on the motor currents Iu to Iw will be described.

  The control means 41 calculates the excitation current Iγ and the torque current Iδ from the data of the motor currents Iu to Iw (hereinafter referred to as the motor currents Iu to Iw) obtained based on the detection of the current detection means 51 to 53. From the torque current Iδ calculation process S1, the excitation current Iγ, the torque current Iδ and the frequency command f *, the next voltage command vectors Vγ1 * and Vδ1 * of the master side inverter circuit 2 and the next voltage command of the slave side inverter circuit 3 From the γ-axis voltage / δ-axis voltage command calculation processing S2 for calculating the vectors Vγ2 * and Vδ2 *, Vγ1 *, Vδ1 *, Vγ2 *, Vδ2 * and the bus voltage Vdc, each phase voltage command Vu1 of the master side inverter circuit 2 * ˜Vw1, each phase voltage command calculation processing S3 for calculating each phase voltage command Vu2 * ˜Vw2 * of the slave side inverter circuit 3, and Vu1 * ˜ In order to drive the electric motor 6 based on the voltage based on the voltage command, the first PWM signals Tup1 to Twn1 to be transmitted to the master side inverter circuit 2 and the slave side inverter circuit 3 are transmitted from w1 * and Vu2 * to Vw2 *. A PWM signal generation process S4 for generating the second PWM signals Tup2 to Twn2 and a PWM signal generation process S5 for transmitting the PWM signals Tup1 to Twn1 (Up1 to Wn1) and Tup2 to Twn2 (Up2 to Wn2) to each inverter circuit are performed. . Here, the control means 41 performs all processing, but each processing device divided in hardware may perform each processing.

  Here, the current detection of the current detection means 51-53 is demonstrated first. Regardless of the connection state of the motor winding specifications, the master-side inverter circuit 2 drives the motor 6 by PWM. During driving operation, there is a time zone in which the lower arm of the master-side inverter circuit 2 is simultaneously turned on in one carrier, except during high-speed / high-load driving (voltage saturation region). For example, when the switching element ON state is 1 and the OFF state is 0, the switching state of each phase is expressed as (W-phase lower arm state, V-phase lower arm state, U-phase lower arm state) = (1, 1, 1). be able to. In this time zone, current flows in all the current detection elements 11a to 11c. Therefore, at this timing, the control means 41 can acquire the motor currents Iu to Iw for three phases by signal transmission from the current detection means 51 to 53 (amplifier, AD converter, etc.).

  In addition, in the time zone in the voltage saturation region described above, it is not possible to obtain motor currents for three phases at the same time, but when the other motors 6 are in driving operation, current data for two phases can be obtained in each carrier cycle. it can. The switching states at this time are (W-phase upper arm state, V-phase upper arm state, U-phase upper arm state) = (1, 1, 0), (1, 0, 1), (0, 1, 1) Become. At this time, the remaining one-phase motor current can be calculated using the principle of three-phase equilibrium of the motor (Iu + Iv + Iw = 0). In this way, motor currents for three phases can be obtained.

  Here, in this Embodiment, the example which detects the electric current which flows into the electric current detection elements 11a-11c inserted between the lower arm of the master side inverter circuit 2 and DC bus was shown. However, the present invention is not limited to this, and the current flowing through the resistor inserted in the DC bus of the master side inverter circuit 2 or the current of the motor 6 is detected by inserting a current transformer between the master side inverter and the motor winding. Thus, a three-phase motor current may be obtained.

  After obtaining the three-phase current data Iu to Iw from the current detection means 51 to 53 as described above, the excitation current Iγ and the torque current Iδ are calculated in the excitation current Iγ / torque current Iδ calculation process S1.

  In the excitation current Iγ / torque current Iδ calculation process S1, the motor currents Iu to Iw are converted into an excitation current (γ-axis current Iγ) and a torque current component (δ-axis current Iδ). Specifically, the excitation current Iγ and the torque current Iδ are calculated by substituting and converting the motor currents Iu to Iw into the conversion matrix [C1] as shown in the following formula (1). However, (theta) in (1) shows an inverter rotation angle, and the case where a rotation direction is clockwise.

  When a sensor for detecting the rotor position such as a pulse encoder is used, the electrical angular frequency of the rotor and the rotational frequency of the inverter circuit substantially coincide with each other. Therefore, the inverter circuit has the same frequency as the electrical angular frequency of the rotor. A rotating coordinate system is generally referred to as a dq coordinate system. On the other hand, when a sensor for detecting the rotor position, such as a pulse encoder, is not used, the dq axis coordinates cannot be accurately captured by the control means 41, and in actuality, the inverter circuit is shifted by a phase difference Δθ from the dq coordinate system. Is rotating. Assuming such a case, a coordinate system that rotates at the same frequency as the output voltage of the inverter circuit is generally referred to as a γδ coordinate system, and is handled separately from the rotating coordinate system. Since this embodiment shows an example in the case of not using a sensor, γ and δ are subscripted following this convention.

  Next, various vector control including speed control is performed from the excitation current Iγ, torque current Iδ, and frequency command f * by the γ-axis voltage / δ-axis voltage command calculation means S2, and the next γ-axis voltage command Vγ * and δ-axis are performed. A voltage command Vδ * is obtained.

Here, when the motor winding has a star connection specification (in the case of single operation), the γ-axis voltage command Vγ1 * and the δ-axis voltage command Vδ1 * for the master-side inverter circuit 2 are expressed by the following equation (2). Further, the γ-axis voltage command Vγ2 * and δ-axis voltage command Vδ2 * for the slave-side inverter circuit 3 are set to 0 as shown in the equation (2) or either hardware or software is set by the control means 41. Through this process, the operation of the slave-side inverter circuit 3 is stopped or prohibited.
Vγ1 * = Vγ *
Vδ1 * = Vδ *
Vγ2 * = 0
Vδ2 * = 0 (2)

When the motor winding is an open winding specification (in the case of cooperative operation), it is necessary to allocate the output Vγ * and Vδ * to the two inverter circuits. Although voltage allocation to each inverter circuit can be realized by various methods, here, as an example, a method for outputting each phase output voltage at an arbitrary ratio in the opposite direction will be described. In order to output each phase output voltage in the opposite direction at an arbitrary ratio, Vγ * and Vδ * may be assigned to each inverter circuit at an arbitrary ratio. At this time, the γ-axis voltage command Vγ1 * and δ-axis voltage command Vδ1 * of the master side inverter circuit 2 and the γ-axis voltage command Vγ2 * and δ-axis voltage command Vδ2 * of the slave side inverter circuit 3 are expressed by the following equation (3). It is. However, k shows the arbitrary values of 0-1.
Vγ1 * = k · Vγ *
Vδ1 * = k · Vδ *
Vγ2 * = (1-k) · Vγ *
Vδ2 * = (1-k) · Vδ * (3)

  Next, each phase voltage command calculation means S3 obtains each phase voltage command Vu1 * to Vv1 * of the master side inverter circuit 2 using the following equation (4) which is an inverse matrix [C1] -1 of the equation (1). . Further, in order to output each phase output voltage in the opposite direction, the slave is obtained by using the following equation (5) in which the inverter rotation angle has a phase difference of 180 degrees with respect to the inverse matrix [C1] -1 of the equation (1). Each phase voltage command Vu2 * to Vv2 * of the side inverter circuit 3 is obtained. As described above, since the allocation of voltage vectors (magnitude and phase) to each inverter circuit has a high degree of freedom, the synthesis of the voltage vectors of the master-side inverter circuit 2 and the slave-side inverter circuit 3 is γ as required. Calculation and setting are made so as to match the combined voltage vector of the shaft voltage command Vγ * and the δ-axis voltage command Vδ *.

  Next, the PWM signal duty generation processing S4 is obtained from the phase voltage commands Vu1 * to Vv1 * of the master side inverter circuit 2, the phase voltage commands Vu2 * to Vv2 * of the slave side inverter circuit 3, and the voltage detection means 54. Based on the ratio to the bus voltage Vdc (the ratio of each phase voltage command to Vdc), the ON time or OFF time of each arm is calculated.

  The PWM signal obtained by converting the switching time in one carrier cycle calculated in this way is transmitted to the master-side inverter circuit 2 as the first PWM signals Tup1 to Twn1 by the PWM signal generation process S5. The slave side inverter circuit 3 outputs the second PWM signals Tup2 to Twn2. In the master side inverter circuit 2, the switching elements 7a to 7f are operated based on the PWM signals Tup1 to Twn1, and in the slave side inverter circuit 3, the switching elements 8a to 8f are operated based on the PWM signals Tup2 to Twn2. A corresponding pulse voltage is applied to drive the motor 6.

  Here, especially when the motor winding specification is a star connection specification, the switching elements 8a to 8f of the slave-side inverter circuit 3 are always OFF (for example, the second PWM signal from the control means 41). Is a HI active (positive logic) signal, the second PWM signals Tup2 to Twn2 are all stuck to the output LO).

  FIG. 3 is a diagram showing a waveform example of a voltage (output voltage) applied to the electric motor 6 from each inverter circuit. Here, it is assumed that the U-phase output voltage waveform is represented. Further, in FIG. 3, in order to visualize the PWM waveform, a waveform (a waveform after passing through the low-pass filter) in which the frequency band near the carrier frequency is attenuated is shown. FIG. 3A shows an example when the motor winding specification is a star connection specification (during independent operation). FIG. 3B shows an example when the motor winding specification is an open winding specification (in the case of cooperative operation).

  FIG. 4 is a diagram illustrating the switching signal E transmitted to the short circuit 23. Next, a method for switching the connection (connection) state of the motor windings will be described. The connection (connection) state is data related to the drive frequency such as the frequency command f *, the actual frequency fm, the estimated frequency fe (effective when performing position sensorless control as in the present embodiment) (hereinafter simply referred to as the drive frequency). ), Based on load torque data representing the load of the electric motor 6 (hereinafter referred to as load torque), the control means 41 makes a determination and transmits a switching signal E. The short circuit 23 performs a switching operation based on the received switching signal E.

  In the example of FIG. 4, the logic of the short circuit 23 is set to HI active. When the drive frequency is low compared to a predetermined value (the position of point A in FIG. 4) and the load torque is small, the switching signal E is set to HI and the short circuit 23 (short circuit switch 22) is turned on. Put it in a state. At this time, the motor winding specification is star connection (single operation). When the drive frequency is higher than the predetermined value and the load torque is large, the switching signal E is set to LO, and the short circuit 23 (short circuit switch 22) is turned OFF. At this time, the motor winding specification is an open winding specification (cooperative operation). Here, the logic circuit setting of the short circuit 23 is HI active (positive logic) setting, but the circuit logic setting can be arbitrarily set according to the circumstances of the hardware side and the software side.

  In the conventional apparatus configuration, it is necessary to provide a large number of switches for switching, but in the present embodiment, it is only necessary to provide the short circuit 23, and the number of switches can be reduced. Therefore, switching management of the connection state becomes easy. Also, the switching state transition time can be shortened. Therefore, it can be applied not only to the induction motor but also to the synchronous motor. However, in a synchronous motor, if sudden switching is performed, depending on the state of the load, there is a possibility that an unstable driving operation may occur such as a current jumping rapidly or a voltage fluctuation. However, it may be difficult to switch the connection state. In order to cope with such a case, a method for controlling the operation of each inverter circuit that enables smooth switching of the motor winding specifications will be described.

  FIG. 5 is a diagram showing a procedure of operation control related to transition of connection specifications. Based on FIG. 5, the concept of the voltage vector applied to each phase is shown and the transition of a connection state is demonstrated. First, the case of shifting from the star connection specification to the open winding specification will be described. Here, before and after the point A in FIG. 4, a region for transition is provided in order to smoothly switch the connection state while maintaining the synchronous operation (the driving operation of the electric motor 6 in this region is referred to as boundary mode operation).

  As shown in FIG. 5, in the star connection specification, k = 1 as shown in the above-described equation (3). That is, the voltage generation ratio by the operation of the master side inverter circuit 2 is 100%. The slave-side inverter circuit 3 is in an output-prohibited or stopped state. In this state, the short circuit 23 is in an ON state.

  When the control means 41 determines that the drive frequency and the drive torque have increased and have exceeded the first predetermined value A1 before point A, the control means 41 shifts the electric motor 6 to the boundary mode operation. The control means 41 uses the second PWM signal transmitted to the slave-side inverter circuit 3 to reduce the unstable phenomenon with respect to the voltage fluctuation at the time of switching the connection specifications, in order to reduce the neutral point potential of each phase (half the bus voltage, intermediate voltage) ) Is output (applied). Specifically, from the slave-side inverter circuit 3 side, the electric motor 6 is driven and operated with the duty ratio of the voltage applied to each phase within the carrier cycle set to 50 [%].

  When it is determined that the driving frequency and driving torque have reached point A, the control means 41 changes the switching signal E from HI to LO, switches the switching operation by the short circuit 23 from ON to OFF, and starts the motor winding specifications. Switch from connection specification to open winding specification.

  In this manner, by outputting the neutral point potential for each phase from the slave-side inverter circuit 3 in advance, the motor winding specifications in the short circuit 23 can be smoothly switched. Thereafter, the control means 41 sets k to an arbitrary ratio based on the equation (3), and the inverter circuit applies a voltage at a predetermined ratio to perform a cooperative operation, while operating the motor 6 in a cooperative manner.

  Next, the case of shifting from the open winding specification to the star connection specification will be described. In the open winding specification, k is an arbitrary value (0 ≦ k ≦ 1) as shown in the above-described equation (3). For this reason, the master-side inverter circuit 2 and the slave-side inverter circuit 3 are cooperatively operated at a ratio based on k. In this state, the short circuit 23 is in an OFF state.

  When the control means 41 determines that the drive frequency and the drive torque have decreased and exceeded a second predetermined value A2 before point A in FIG. 4, the control means 41 shifts to boundary mode operation. First, the transition is made so that k becomes 1 over a predetermined time, and the line voltage is generated only by the master-side inverter circuit 2. Thereafter, the control means 41 uses the second PWM signal transmitted to the slave-side inverter circuit 3 to reduce the unstable phenomenon with respect to the voltage fluctuation at the time of switching the connection state. ) Is output. Specifically, from the slave-side inverter circuit 3 side, the electric motor 6 is driven and operated with the duty ratio of the signal of each phase set to 50 [%] within the carrier cycle.

  If it is determined that the drive frequency and drive torque have reached point A, the control means 41 changes the switching signal E from LO to HI, and switches the operation of the short circuit 23 from OFF to ON to change the motor winding specification to the open winding specification. Switch to the star connection specification. By outputting the neutral point potential for each phase in advance by the slave inverter circuit 3, the short circuit can be switched smoothly. Thereafter, by stopping the output of the slave side inverter circuit 3, the transition to the operation of only the master side inverter circuit 2 is completed.

  FIG. 6 is a diagram illustrating an example of a command voltage and a switching signal E in an arbitrary phase when the operating state is switched. FIG. 6A shows that a predetermined pause period (time, for example, a dead time period of the switching element or more) has elapsed since all the switching elements 8a to 8f of the slave-side inverter circuit 3 are turned OFF during the boundary mode operation. This represents a method for switching the short circuit 23 to the ON state later. FIG. 6B shows a method of switching the short circuit 23 to the ON state at the moment when all the switching elements 8a to 8f of the slave side inverter circuit 3 are turned OFF during the boundary mode operation.

  For example, when there is a concern about noise at the time of switching, the motor winding specifications are switched using the method shown in FIG. On the other hand, when quick switching is required, the motor winding specifications are switched using FIG.

  As described above, the method of outputting (applying) each phase neutral point potential (half the bus voltage, intermediate voltage) at the time of switching the connection specifications by the second PWM signal transmitted to the slave-side inverter circuit 3 has been shown. If it is desired to switch the connection specifications in a shorter time, the following method may be used.

  FIG. 7 shows the operation related to the transition of the connection specification without passing through the neutral point potential (half potential of the bus voltage, intermediate voltage) at the time of switching the connection specification by the second PWM signal transmitted to the slave side inverter circuit 3. It is a figure which shows the procedure of control. Based on FIG. 7, the concept of the voltage vector applied to each phase is shown and the transition of a connection state is demonstrated. First, the case of shifting from the star connection specification to the open winding specification will be described. Here, before and after the point A in FIG. 4, the connection state is switched immediately without passing through the boundary mode operation while maintaining the synchronous operation.

  As shown in FIG. 7, in the star connection specification, k = 1 as shown in the above-described equation (3). At this time, the voltage generation ratio by the operation of the master side inverter circuit 2 is 100%. The slave-side inverter circuit 3 is in an output-prohibited or stopped state. In this state, the short circuit 23 is in an ON state.

  When the control means 41 determines that the drive frequency and the drive torque have increased and exceeded the first predetermined value A1 before point A, the control means 41 shifts the electric motor 6 to cooperative operation.

  When it is determined that the driving frequency and driving torque have reached point A, the control means 41 changes the switching signal E from HI to LO, switches the switching operation by the short circuit 23 from ON to OFF, and starts the motor winding specifications. Switch from connection specification to open winding specification.

  As described above, the motor winding specifications in the short circuit 23 are immediately switched without outputting the neutral point potential from each phase from the slave inverter circuit 3 in advance. . Thereafter, the control means 41 sets k to an arbitrary ratio based on the equation (3), and the inverter circuit applies a voltage at a predetermined ratio to perform a cooperative operation, while operating the motor 6 in a cooperative manner.

  Next, the case of shifting from the open winding specification to the star connection specification will be described. In the open winding specification, k is an arbitrary value (0 ≦ k ≦ 1) as shown in the above-described equation (3). For this reason, the master-side inverter circuit 2 and the slave-side inverter circuit 3 are cooperatively operated at a ratio based on k. In this state, the short circuit 23 is in an OFF state.

  When the control means 41 determines that the drive frequency and the drive torque have dropped and have exceeded the second predetermined value A2 before point A in FIG. 4, the control means 41 shifts so that k becomes 1 over a predetermined time, The line voltage is generated only by the master side inverter circuit 2.

  If it is determined that the drive frequency and drive torque have reached point A, the control means 41 changes the switching signal E from LO to HI, and switches the operation of the short circuit 23 from OFF to ON to change the motor winding specification to the open winding specification. Switch to the star connection specification. By switching the short circuit without outputting the neutral point potential in advance for each phase in the slave-side inverter circuit 3, the connection can be switched in a short time. Thereafter, by stopping the output of the slave side inverter circuit 3, the transition to the operation of only the master side inverter circuit 2 is completed.

  FIG. 8 is a diagram illustrating an example of a command voltage and a switching signal E in an arbitrary phase when the operating state is switched. FIG. 8A shows that the short-circuit 23 is turned on after a predetermined pause period (for example, the dead time period of the switching element or more) elapses after all the switching elements 8a to 8f of the slave-side inverter circuit 3 are turned off. Represents a method for switching to a state. FIG. 8B shows a method of switching the short circuit 23 to the ON state at the moment when all the switching elements 8a to 8f of the slave side inverter circuit 3 are turned OFF.

  For example, when there is a concern about noise at the time of switching, the motor winding specifications are switched using the method shown in FIG. On the other hand, when quick switching is required, the motor winding specifications are switched using FIG.

  As described above, according to the electric motor drive device of the present embodiment, the master side inverter circuit 2 and the slave side inverter circuit 3 are connected to the lead wire of the electric motor 6 to connect the star connection specification and the open winding specification. Therefore, even if the inverter circuit does not correspond to a large capacity, the motor winding specifications of the motor can be switched. At that time, since the short circuit 23 is used to switch the motor windings related to each phase, the switching elements 8a to 8f of the slave side inverter circuit 3 are all turned on in the star connection specification. There is no need to short circuit and form a closed circuit. For this reason, the number of switches to be managed is small, the motor winding specifications can be switched quickly, and it is easy to cope with variations between elements related to the switches, so that the reliability of the system can be increased.

  Moreover, since the switch of the short circuit 23 is only the short switch 22, the loss due to the switching element can be made smaller than before depending on the operating conditions (motor power factor, modulation factor). Further, even if the switching element open failure of the slave side inverter circuit 3 or the disconnection with the electric motor 6 occurs, the driving operation of the electric motor 6 by the star connection specification can be continued only by the master side inverter circuit 2. Therefore, the reliability of the system can be increased. And since the area | region for performing a boundary mode driving | operation was provided, a connection specification can be switched smoothly and quickly, maintaining a synchronous driving | operation, and it can respond also to a synchronous motor. Further, when switching the connection specifications in a shorter time, the switching operation can be performed quickly without performing the boundary mode operation.

Embodiment 2. FIG.
FIG. 9 is a diagram illustrating a configuration example of the short circuit 23 according to the second embodiment. In the present embodiment, a short circuit 23 that realizes switching of winding specifications will be described. In FIG. 9, the transistor 26 is turned on (conducts) based on the switching signal E from the control means 41. The photocoupler 25 includes a light emitting diode and two transistors that are light receiving elements. When the transistor 26 is turned on, the light emitting diode emits light, and the received transistor is turned on.
In the present embodiment, the short-circuit switch 22 is a semiconductor switch such as a MOS-FET. When the transistor of the photocoupler 25 is turned on, the voltage application of the gate is changed to be turned on. Thereby, the neutral point side of the motor winding of each phase connected to the three-phase rectifier circuit 21 is electrically connected, and the motor winding specification becomes the star connection specification as described above. When the short circuit switch 22 is in the OFF state, the current from the motor 6 stops flowing, and the motor winding specification becomes the open winding specification.

  Next, an operation when the short circuit 23 is turned on will be described. When the switching signal E from the control means 41 is HI, the transistor 26 is turned on. As a result, in the photocoupler 25, the light emitting diode emits light, and the transistor receiving the light conducts. In conjunction with this, the short-circuit switch 22 is turned ON. When the short-circuit switch 22 is turned on, the neutral point side of the motor winding can be electrically connected via the three-phase rectifier circuit 21.

  In this way, by performing photo-insulation using the photocoupler 25, the source of the short-circuit switch 22 and the emitter-side potential of the transistor located in the lower stage of the photocoupler 25 are insulated from the potential of the transistor 26. Thereby, the short circuit switch 22 is not inadvertently turned ON or OFF due to noise or the like, and the electric motor 6 can be driven and operated safely and with high reliability.

  Further, since the semiconductor switch is used as the short-circuit switch 22, the width of the region where the boundary mode operation is performed can be narrowed, and the motor winding specifications can be quickly switched. Furthermore, since a low-resistance MOS-FET or the like is used as the short-circuit switch 22, switching is performed in comparison with a case where all of the switching elements of the slave-side inverter circuit 3 are turned on (conducted) to make a star connection specification. The total loss can be reduced as compared with the case of using an element. In particular, when the motor current is small, the effect of reducing loss is great, and further improvement in efficiency can be expected. Further, depending on the operating point, power factor, modulation factor, etc. when driving the motor, it is possible to operate with high efficiency.

Embodiment 3 FIG.
FIG. 10 is a diagram illustrating an example of the relationship between the overall efficiency of driving operation and the driving frequency. The motor drive device described in the above-described embodiment and the like is basically one of the purposes to obtain a large load torque at the start. However, if the motor winding specification of the motor 6 is switched to the star connection specification or the open winding specification under a predetermined condition, it is possible to drive the motor 6 with emphasis on high efficiency. For example, in a system in which high efficiency is prioritized, as shown in FIG. 8, the relationship between the drive frequency, load torque, and overall efficiency is determined in advance by experiments or the like. It is obtained by driving. Then, the short-circuit 23 is switched on or off by a switching signal E at a predetermined value X at which the overall efficiency in the star connection specification and the open winding specification is reversed. Here, both the reference of switching the short circuit 23 from ON to OFF and switching from OFF to ON are both set to the predetermined value X. However, for example, hysteresis may be provided.

  Further, when the switching element of the slave side inverter circuit 3 is broken open, or when a disconnection occurs between the electric motor 6 and the slave side inverter circuit 3, the conventional system cannot be operated regardless of connection. Become. However, in this electric motor drive device, only the master-side inverter circuit 2 can be operated and the electric motor 6 can be driven by the star connection specification.

  For example, before starting the driving operation of the electric motor 6, if a sequence for detecting a failure of the slave side inverter circuit 3 is mounted by superimposing a DC voltage on each winding, the slave side inverter circuit 3 Is determined to be a failure, the motor 6 can be driven at a low speed only by the operation of the master-side inverter circuit 2. Therefore, the reliability as a system can be improved.

Embodiment 4 FIG.
FIG. 11 is a diagram illustrating an example of a system configuration centering on an electric motor drive device when a plurality of short-circuit switches according to Embodiment 4 are used. In the first to third embodiments described above, the case where one short-circuit switch in the short circuit 23 is used has been described. However, as shown in FIG. 11, a plurality of short-circuit switches may be used. By using a plurality of short-circuit switches, system operation can be continued even when one element has an open failure. Further, for example, it is advantageous to reduce the current capacity per element when cost merit is obtained. Further, current concentration on one element can be prevented, which is advantageous in terms of thermal design.

  FIG. 12 is a diagram illustrating a configuration example of the short circuit 23. At this time, as shown in FIG. 12, the switching signal E from the control means 41 is sent to the shorting switches 22a to 22b via the shorting switch state switching circuit 24, so that the state of the shorting switch can be switched. . The short-circuit switch state switching circuit 24 is configured by a circuit as shown in FIG. 7, and the output is branched into a plurality (two paths when there are two short-circuit switches as in FIG. 12) and sent to each short-circuit switch. You may do it. Further, the switching signal E from the control means 41 is branched, and a plurality of short-circuit switch state switching circuits 24 (two when there are two short-circuit switches as shown in FIG. 12) are output to each short-circuit switch. And you may make it send.

Embodiment 5 FIG.
FIG. 13 is a configuration diagram of a refrigeration air conditioning apparatus according to Embodiment 4 of the present invention. In the present embodiment, an air conditioner will be described as an example of a refrigerated air conditioner. The air conditioning apparatus of FIG. 13 includes a heat source side unit (outdoor unit) 100 and a load side unit (indoor unit) 200, which are connected by a refrigerant pipe, and are a main refrigerant circuit (hereinafter referred to as a main refrigerant circuit). And the refrigerant is circulated. Among the refrigerant pipes, a pipe through which a gaseous refrigerant (gas refrigerant) flows is referred to as a gas pipe 300, and a pipe through which a liquid refrigerant (liquid refrigerant, which may be a gas-liquid two-phase refrigerant) flows is referred to as a liquid pipe 400.

  In the present embodiment, the heat source side unit 100 includes a compressor 101, an oil separator 102, a four-way valve 103, a heat source side heat exchanger 104, a heat source side fan 105, an accumulator (gas-liquid separator) 106, and a heat source side expansion device. (Expansion valve) 107, an inter-refrigerant heat exchanger 108, a bypass expansion device 109 and a heat source side control device 111.

  The compressor 101 has the electric motor 6 described in the above-described embodiment, sucks the refrigerant, compresses the refrigerant, and converts it into a high-temperature / high-pressure gas state to flow through the refrigerant pipe. Regarding the operation control of the compressor 101, for example, the compressor 101 is provided with the master-side inverter circuit 2, the slave-side inverter circuit 3 and the like described in the above-described embodiment, and the operation frequency is arbitrarily changed. It is assumed that the capacity (the amount of refrigerant sent out per unit time) can be finely changed.

  The oil separator 102 separates the lubricating oil 16 discharged from the compressor 101 mixed with the refrigerant. The separated lubricating oil 16 is returned to the compressor 101. The four-way valve 103 switches the refrigerant flow between the cooling operation and the heating operation based on an instruction from the heat source side control device 111. The heat source side heat exchanger 104 performs heat exchange between the refrigerant and air (outdoor air). For example, during the heating operation, it functions as an evaporator, performs heat exchange between the low-pressure refrigerant that has flowed in through the heat source side expansion device 107 and air, and evaporates and vaporizes the refrigerant. Further, during the cooling operation, it functions as a condenser and performs heat exchange between the refrigerant compressed in the compressor 101 flowing in from the four-way valve 103 side and air, thereby condensing and liquefying the refrigerant. The heat source side heat exchanger 104 is provided with a heat source side fan 105 in order to efficiently exchange heat between the refrigerant and the air. The heat source side fan 105 may also have an inverter circuit (not shown), and the fan motor operating frequency may be arbitrarily changed to finely change the rotation speed of the fan.

  The inter-refrigerant heat exchanger 108 exchanges heat between the refrigerant flowing in the main flow path of the refrigerant circuit and the refrigerant branched from the flow path and adjusted in flow rate by the bypass expansion device 109 (expansion valve). . In particular, when it is necessary to supercool the refrigerant during the cooling operation, the refrigerant is supercooled and supplied to the load side unit 200. The liquid flowing through the bypass throttle device 109 is returned to the accumulator 106 via the bypass pipe 107. The accumulator 106 is means for storing, for example, liquid excess refrigerant. The heat source side control device 111 is composed of, for example, a microcomputer. It can be wired or wirelessly communicated with the load-side control device 204, for example, based on data relating to detection of various detection means (sensors) in the air conditioner, operation frequency control of the compressor 101 by inverter circuit control, etc. The respective units related to the air conditioner are controlled to control the operation of the entire air conditioner. Here, in the present embodiment, for example, the heat source side control device 111 performs the processing of the control means 41 in the first embodiment described above.

On the other hand, the load side unit 200 includes a load side heat exchanger 201, a load side expansion device (expansion valve) 202, a load side fan 203, and a load side control device 204. The load side heat exchanger 201 performs heat exchange between the refrigerant and air. For example, during heating operation, it functions as a condenser, performs heat exchange between the refrigerant flowing in from the gas pipe 300 and air, condenses and liquefies the refrigerant (or gas-liquid two-phase), and moves to the liquid pipe 400 side. Spill. On the other hand, during the cooling operation, it functions as an evaporator, performs heat exchange between the refrigerant and the air whose pressure is reduced by the load-side throttle device 202, causes the refrigerant to take heat of the air, evaporates it, and vaporizes it. It flows out to the piping 300 side.
In addition, the load side unit 200 is provided with a load side fan 203 for adjusting the flow of air for heat exchange. The operating speed of the load-side fan 203 is determined by, for example, user settings. The load side expansion device 202 is provided to adjust the pressure of the refrigerant in the load side heat exchanger 201 by changing the opening degree.

  The load-side control device 204 is also composed of a microcomputer or the like, and can communicate with the heat source-side control device 111 by wire or wireless, for example. Based on an instruction from the heat source side control device 111 and an instruction from a resident or the like, for example, each device (means) of the load side unit 200 is controlled so that the room has a predetermined temperature. Further, a signal including data related to detection by the detection means provided in the load side unit 200 is transmitted.

  Next, the operation of the air conditioner will be described. First, basic refrigerant circulation in the main refrigerant circuit during cooling operation will be described. Due to the driving operation of the compressor 101, the high-temperature, high-pressure gas (gas) refrigerant discharged from the compressor 101 is condensed by passing through the heat source side heat exchanger 104 from the four-way valve 103 and becomes a liquid refrigerant. The side unit 100 flows out. The refrigerant flowing into the load side unit 200 through the liquid pipe 400 evaporates as the low temperature and low pressure liquid refrigerant whose pressure is adjusted by adjusting the opening degree of the load side expansion device 202 passes through the load side heat exchanger 201. leak. Then, it flows into the heat source side unit 100 through the gas pipe 300, is sucked into the compressor 101 through the four-way valve 103 and the accumulator 106, and is circulated by being pressurized and discharged again.

  Further, basic refrigerant circulation in the main refrigerant circuit during heating operation will be described. Due to the driving operation of the compressor 101, the high-temperature, high-pressure gas (gas) refrigerant discharged from the compressor 101 flows into the load side unit 200 from the four-way valve 103 through the gas pipe 300. In the load-side unit 200, the pressure is adjusted by adjusting the opening degree of the load-side expansion device 202, and condensed by passing through the load-side heat exchanger 201 to become an intermediate-pressure liquid or a gas-liquid two-phase refrigerant. And flows out of the load side unit 200. The refrigerant flowing into the heat source side unit 100 through the liquid pipe 400 is pressure-adjusted by adjusting the opening degree of the heat source side expansion device 107, evaporates by passing through the heat source side heat exchanger 104, and becomes a gas refrigerant. Then, the refrigerant is sucked into the compressor 101 through the four-way valve 103 and the accumulator 106, and circulated by being pressurized and discharged as described above.

  As described above, according to the refrigeration air conditioner of the fifth embodiment, the air conditioner that is a refrigeration cycle apparatus is configured using the compressor 101 that is operated by inverter control by the electric motor drive device according to the above-described embodiment. Since it did in this way, it can respond also when the load at the time of starting is large, and in the compressor 101 especially important in an air conditioning apparatus, reliability is high and it can aim at reduction of processing cost. Therefore, the air conditioning apparatus as a whole is highly reliable and can reduce costs.

Embodiment 6 FIG.
In the above-described fourth embodiment, the air conditioner has been described as the refrigeration cycle apparatus, but is not limited thereto. For example, the present invention can also be used for a cooling device, a heat pump device, and the like used for freezing and refrigerated warehouses.

It is a figure showing an example of the system configuration centering on an electric motor drive device. It is a figure showing the flowchart which creates a PWM signal. It is a figure which shows the waveform example of the voltage (output voltage) from each inverter circuit. It is a figure showing the setting of the switching signal E transmitted to the short circuit 23. It is a figure which shows the procedure of a transfer of a connection state. It is a figure showing the example of the command voltage which concerns on the switching of an operating state, and the switching signal E. FIG. It is a figure which shows the procedure which makes a connection state transfer, without passing through each phase neutral point electric potential. It is a figure showing the example of the command voltage and switching signal E when not passing through each phase neutral point potential. 5 is a diagram illustrating a configuration example of a short circuit 23 according to Embodiment 2. FIG. It is a figure showing the example of a relationship between the total efficiency of drive operation, a drive frequency, etc. It is a figure showing the example of a system configuration at the time of using two or more short-circuit switches. It is a figure showing the example of a structure of the short circuit 23 which uses multiple short circuit switches. 6 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 5. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 DC voltage source, 2 Master side inverter main circuit, 3 Slave side inverter circuit (three-phase bridge circuit), 6 Electric motor, 7a-7f, 8a-8f Switching element, 9a-9f, 10a-10f Diode, 11a-11c, DESCRIPTION OF SYMBOLS 12 Current detection element, 21 3 phase rectifier circuit, 22, 22a-22b Short circuit switch, 23 Short circuit, 24 Short circuit switch state switching circuit, 25 Photocoupler, 26 Transistor, 31 Electronic board, 41 Control means, 51-53 Current detection Means, 54 voltage detection means, 100 heat source side unit, 101 compressor, 102 oil separator, 103 four-way valve, 104 heat source side heat exchanger, 105 heat source side fan, 106 accumulator, 107 heat source side throttle device, 108 heat exchange between refrigerants , 109 Bypass throttle device, 110 Heat source side Control device, 200 a load-side unit, 201 load side heat exchanger, 202 load-side throttle device, 203 a load-side fan, 204 load controller, 300 a gas pipe, 400 liquid pipe.

Claims (15)

A master-side inverter circuit that performs an operation for driving the motor by applying a voltage by PWM based on a first PWM signal, connected to a lead wire of the motor drawn by separating a neutral point of the motor winding,
A slave-side inverter circuit that is connected to a separate lead line from the master-side inverter circuit and performs an operation for driving the motor based on a second PWM signal;
One short-circuit switch used for short-circuit switching of the neutral point, and based on a switching signal, the star connection specification for driving the electric motor by the operation of only the master-side inverter circuit, or the master-side inverter circuit and the A short circuit that connects the lead wire in parallel with the slave side inverter circuit to switch the motor winding specification of the motor to one of the open winding specifications that drive the motor by a cooperative operation with the slave side inverter circuit. When,
An electric motor drive device comprising: control means for transmitting the first PWM signal and the second PWM signal to the master side inverter circuit and the slave side inverter circuit, and transmitting the switching signal to the short circuit. The short circuit, motor drive system of claim 1, wherein further comprising a three-phase rectifier circuit. The short-circuit switch is motor drive system of claim 1, wherein it is a semiconductor switch. The short circuit, by turning ON the short-circuit switch on the basis of a switching signal transmitted from the control unit, according to claim 1, characterized in that the motor windings specification a star connection specification of the electric motor The electric motor drive device in any one. The control means transmits a switching signal for turning on the short circuit switch to the short circuit, and transmits a second PWM signal for turning off all the arms of the slave side inverter circuit to the slave side inverter circuit. The electric motor drive device according to any one of claims 1 to 4 . The control means transmits a switching signal for turning off the short-circuit switch to the short-circuit, and the first PWM signal and the second PWM signal that cause the master-side inverter circuit and the slave-side inverter circuit to operate in cooperation with each other. The motor drive device according to any one of claims 1 to 4 , wherein the motor drive device is transmitted to the slave-side inverter circuit. The reference potential for switching ON or OFF of the short-circuit switch and the reference potential in a circuit relating to driving operation of the electric motor 6 are distinguished by electrically insulating the circuits . The electric motor drive device according to any one of 6 . The control means is either the star connection specification or the open winding specification based on the actual frequency, the frequency command, the estimated frequency, or the load of the motor related to the operation of the master side inverter circuit and the slave side inverter circuit. The electric motor drive device according to any one of claims 1 to 7 , wherein the electric motor drive device according to any one of claims 1 to 7 , further comprising: determining whether to perform the operation and transmitting the switching signal based on the determination to the short circuit. The control means is for switching a motor winding specification of the motor to the short circuit while transmitting a second PWM signal for applying an intermediate voltage to each phase of the motor to the slave-side inverter circuit. The electric motor drive apparatus according to claim 1 , wherein the switching signal is transmitted. 10. The motor driving device according to claim 9, wherein the intermediate voltage is applied with a duty ratio of a pulse width of a voltage applied to each phase being set to 50%. The control means causes the slave-side inverter circuit to apply an intermediate voltage to each phase of the electric motor, and further turns off all the switching elements constituting the slave-side inverter circuit and after a predetermined pause time has elapsed. 11. The electric motor drive device according to claim 9, wherein the switching signal for turning on the short-circuit switch is transmitted. The control means causes the slave-side inverter circuit to apply an intermediate voltage to each phase of the motor, and further turns off the short-circuit switch when all the switching elements constituting the slave-side inverter circuit are turned off. The motor drive device according to claim 9 or 10, wherein the switching signal is transmitted. The control means turns off the short-circuit switch when starting application of a line voltage to each phase of the motor by a second PWM signal, and prohibits or stops output of the second PWM signal to each phase of the motor. motor driving device according to any one of claims 1 to 8, characterized in that turning oN the short-circuit switch when the normally turned off. A compressor that has an electric motor driven by the electric motor driving device according to any one of claims 1 to 13 and compresses a refrigerant;
A condenser that condenses the refrigerant by heat exchange;
A throttle device for reducing the pressure of the condensed refrigerant;
A refrigerating air conditioner comprising: a refrigerant circuit configured by pipe-connecting an evaporator configured to exchange heat between the decompressed refrigerant and air to evaporate the refrigerant. A master-side inverter circuit that performs an operation for driving the motor by applying a voltage by PWM based on a first PWM signal, connected to a lead wire of the motor drawn by separating a neutral point of the motor winding, A slave side inverter circuit that is connected to a separate lead line from the master side inverter circuit and performs an operation for driving the electric motor based on the second PWM signal, and only the master side inverter circuit based on a switching signal The motor winding of the motor is either a star connection specification for driving the motor by the operation of the above, or an open winding specification for driving the motor by a cooperative operation of the master side inverter circuit and the slave side inverter circuit. In order to switch the specifications, the reference is parallel to the slave inverter circuit. Connected to the out line, in the driving method of the motor driving device and a short circuit having one short-circuiting switch for use in short-circuit switching of the neutral point,
Determining whether to switch the motor winding specifications;
If it is determined to switch, the second PWM signal for applying an intermediate voltage to each phase of the electric motor is transmitted to the slave-side inverter circuit, and the electric motor is switched by switching the one short circuit switch of the short circuit. And a step of transmitting the switching signal for switching the motor winding specifications of the motor to the one short-circuit switch .

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