JP2980025B2 - Motor overcurrent protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a motor, and more particularly to a measure for controlling a supply voltage of the motor.

[0002]

2. Description of the Related Art Conventionally, a compressor of an air conditioner has
Refrigeration and air conditioning handbook (4th edition, published by Japan Refrigeration Association)
As disclosed in pages 375 and 376 of the basic edition, there is a case in which a crankcase heater is attached. That is, although the crankcase of the compressor is filled with the refrigerating machine oil, the refrigerant may enter the refrigerating machine oil when the outside air temperature is low, such as during a stoppage in winter.

If the refrigerant is started with the refrigerant mixed in the refrigerating machine oil, the refrigerant in the refrigerating machine oil boils, so-called oil forming may occur, and the compressor may stop without increasing the oil pressure. Therefore, while the compressor is stopped, the crankcase heater is energized to heat the refrigerating machine oil so that the refrigerant is not mixed.

[0004]

However, in the above-described compressor, since the crankcase heater is used, there is a problem that the number of parts is increased and the structure is complicated. Therefore, it has been considered to energize the electric motor of the compressor to generate heat without rotating the electric motor so as to also serve as a heater.

On the other hand, in a power system for supplying power to a motor of a compressor, as disclosed in Japanese Patent Application Laid-Open No. 5-26172, a current supplied to the motor is detected, and stop control is performed when an overcurrent flows. In some cases, equal protection control is performed. In this protection control, since the overcurrent may be transient, when the overcurrent is detected, the driving operation is retried. Further, if this retry is performed a predetermined number of times, it is considered that an abnormality such as an original short circuit has occurred. Therefore, the retry is terminated, the operation is stopped, and an abnormality display or the like is performed.

However, since the above-mentioned protection control is set to be executed only during the normal air-conditioning operation, there is a problem that the retry limit control does not function when the electric motor is supplied instead of the crankcase heater as described above. there were.

That is, since the preheating operation of the electric motor is performed in a state where the normal air-conditioning operation is stopped at night or the like, it is not natural to display an abnormality. Therefore, when an overcurrent flows, a retry is performed. Will repeat. As a result, there is a problem in that a device of the power conversion circuit is stressed and may be broken.

[0008] The present invention has been made in view of the above point, and when an overcurrent flows during preheating of a motor, stress is not applied to a device of a power conversion circuit to prevent the device from being destroyed. The purpose is to prevent the problem.

[0009]

[Means for Solving the Problems]

-Summary of the Invention- The present invention converts the power supplied from a power supply (PS) into a predetermined controlled three-phase AC power, outputs the converted power to a motor (CM), and pulses the supply voltage of the motor (CM). Power conversion circuit (20) to control the motor (CM) at variable speed by width modulation
On the other hand, if a preheating signal is received while the motor (CM) is stopped, the motor (CM) is energized to generate heat. Further, when the overcurrent detection means (CT) detects an overcurrent during preheating of the motor (CM), the preheating operation is temporarily interrupted, and then the preheating operation is retried. Then, the preheating control ends.

-Specific Items of the Invention- Specifically, as shown in FIG. 1, the means of the invention according to claim 1 first includes a power supply (PS) and a motor (CM). Then, the electric power supplied from the power supply (PS) is converted into a predetermined controlled three-phase AC electric power, and the electric motor (CM)
Power conversion circuit (20) for outputting to the power conversion circuit (2)
0) is provided with a drive circuit (31) for outputting a drive signal. Further, a control signal for controlling a supply frequency of the motor (CM), which is a pulse width modulation of a supply voltage of the motor (CM) to perform variable speed control of the motor (CM), is transmitted to the drive circuit (31). An output speed control means (41) is provided. In addition, an overcurrent detecting means (CT) for detecting an overcurrent flowing through the motor (CM), and when a preheating signal is received while the motor (CM) is stopped, the motor (CM) is energized to supply electric power to the motor (CM). Heat generation control means (43) for outputting a preheat control signal to the drive circuit (31) so as to generate heat when the CM) is stopped is provided. In addition, when the overcurrent detection means (CT) detects an overcurrent during preheating of the motor (CM) by the heat generation control means (43), the preheating operation by the heat generation control means (43) is temporarily stopped, and then the preheating operation is stopped. When the number of retries of the retry means (44) reaches a predetermined number during reheating of the electric motor (CM) by the retry means (44) for retrying the operation and the heat generation control means (43), the preheat control means (43) performs preheating control. And a retry limiter (45) for outputting an end signal for terminating the process.

Further, the means adopted by the invention according to claim 2 is the same as the invention described in claim 1, except that the motor (CM)
Is configured to be a motor of a compressor provided in the air conditioner.

-Operation- According to the above-mentioned invention specifying matter, in the invention of claim 1,
First, when the power supply (PS) is turned on and an operation command is output, the speed control means (41) outputs a control signal, and the drive circuit (31) outputs a drive signal to the power conversion circuit (20), The power supply circuit (20) applies a predetermined supply voltage pulse-modulated to the electric motor (CM).

On the other hand, when the heat generation control means (43) receives the preheating signal while the electric motor (CM) is stopped, for example, according to the second aspect of the invention, when the outside air temperature is low, the air conditioner may be used. Since there is a possibility that refrigerant may be mixed into the refrigerating machine oil of the compressor, the heat generation control means (43) receives the preheating signal and outputs a preheating control signal to the drive circuit (31).

The drive circuit (31) receives the preheating control signal, drives the power conversion circuit (20) to output a predetermined supply voltage to the electric motor (CM), for example, the power conversion circuit (20) outputs. The V-phase supply voltage is output to the electric motor (CM) as a pulse-width-modulated voltage, while the U-phase supply voltage and the W-phase supply voltage are square-wave alternating currents whose cycles correspond to the supply frequency. Then, it is output to the electric motor (CM) as a continuous voltage of a predetermined voltage that is not pulse width modulated. As a result, the motor (C) does not rotate and the motor (C
M) Heats itself and heats the refrigerator oil.

On the other hand, if an overcurrent occurs during preheating of the electric motor (CM), the preheating operation by the heat generation control means (43) is temporarily stopped. That is, in the case of the first overcurrent detection in response to the current signal from the overcurrent detection means (CT), the preheating operation by the heat generation control means (43) is temporarily interrupted, and then the retry means (44) starts the preheating operation. To retry.

While counting the number of retries,
Then, the heat generation control means (4
3) When the preheating operation resumes and overcurrent occurs again,
While repeating the above retry until the predetermined number of times,
When the retry reaches a predetermined number of times, the retry limiting means (45) determines that an overcurrent abnormality has been determined, not a transient overcurrent, but an inherent abnormality such as a short circuit. To end.

[0017]

Therefore, according to the first aspect of the present invention, if an overcurrent is detected during preheating of the electric motor (CM), the preheating operation is retried up to a predetermined number of times. Since it is possible to prevent stress from being applied to devices such as power transistors in the power conversion circuit (20), it is possible to reliably prevent destruction of these devices.

Further, since the motor (CM) is energized to generate heat, the motor (CM) itself also serves as a heater, so that the conventional crankcase heater can be omitted, and as a result, the number of parts can be reduced. Can be reduced.

According to the second aspect of the invention, in the case of the compressor of the air conditioner, since the refrigerant can be reliably prevented from being mixed into the refrigerating machine oil, the compressor is smoothly started. You can do so.

[0020]

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 supplying control power from a power supply (PS) to the induction motor (CM) via the power conversion circuit (20). doing.

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 a 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) as overcurrent detection means for detecting a motor current, which is a current M), is provided in 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 transistor (Tr, Tr,...) Is connected with a freewheeling diode (d2, d2,...) Between the emitter and the collector, and the power transistor (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 portion 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 the room temperature, and 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. 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) so 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.

The CPU (40) is provided with heat generation control means (43), retry means (44), and retry restriction means (45) as features of the present invention. When the preheating signal is received while the induction motor (CM) is stopped, the heat generation control means (43) energizes the induction motor (CM) to turn on the induction motor (C).
M) generates heat, and the power conversion circuit (20) outputs a supply voltage of one phase of the supply voltage of the induction motor (CM) as a pulse width modulated modulation voltage signal, and at the same time, supplies the other two phases of supply voltage. A preheating control signal is output to the drive circuit (31) so that the power conversion circuit (20) outputs a continuous voltage signal that is maintained at a predetermined voltage value without pulse width modulation, and heat is generated without rotating the induction motor (CM). Let it.

Specifically, as shown in FIG. 3, the V-phase supply voltage Sv is output from the power conversion circuit (20) to the induction motor (CM) as a pulse-width-modulated modulation voltage,
The supply voltage Su of the phase and the supply voltage Sw of the W phase are square-wave alternating current corresponding to the supply frequency, and are a continuous voltage of a predetermined voltage not subjected to pulse width modulation. (CM).

Further, the U-phase supply voltage Su and the W-phase supply voltage Sw are formed in the same-phase square-wave AC, and an electric current is prevented from flowing between the U-phase and the W-phase. (CM) is prevented from rotating.

Although not shown, the preheating signal is output or stopped under the following conditions upon receiving a discharge pipe temperature signal from a temperature sensor for detecting a discharge pipe temperature T2 of the compressor. I have.

The preheating signal is generated either between the time when the power supply (PS) is turned on and when the first air conditioning operation is started, or after the compressor has been stopped and 15 minutes or more have elapsed. In this state, when the discharge pipe temperature T2 of the compressor becomes 7 ° C. or less, the output is performed.

In addition, the preheating signal is such that either a temperature control operation start command (thermo-on command) is output or the discharge pipe temperature T2 of the compressor becomes higher than 9.5 ° C. Then, the output is stopped.

On the other hand, when the current transformer (CT) detects an overcurrent during preheating of the induction motor (CM) by the heat generation control means (43), the retry means (44) performs a preheating operation by the heat generation control means (43). Is temporarily stopped, and then the preheating operation is retried. That is, when a transient overcurrent flows, it is preferable to continue the preheating operation, so that the preheating operation is restarted.

If the number of retries of the retry means (44) reaches a predetermined number during the preheating of the induction motor (CM) by the heat generation control means (43), for example, if the retry is repeated four times, the retry limiting means (45) Since there is a high possibility that an abnormality such as an abnormal condition has occurred, an end signal for ending the preheating control is output to the heat generation control means (43).
That is, in the case where the overcurrent is detected a plurality of times, the preheating operation is terminated because it is considered that an original abnormality such as a short circuit has occurred instead of a transient overcurrent.

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

First, in the state where the power supply (PS) is turned on and the switching circuit (11) is turned on, when an operation command such as a cooling operation is output from a remote controller (not shown), the CPU (40) receives the operation command. Then, the speed control means (41) outputs a control signal. The control signal is received by the drive circuit (31), and the drive signal is output to the inverter circuit (23), and 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 a rectifier circuit (21), is converted to DC, is smoothed by a smoothing circuit (22), and is then smoothed by an inverter circuit (22). Output to 23). And six power transistors (Tr, Tr,...) Of the inverter circuit (23).
Converts a direct current into an alternating current and supplies a predetermined supply voltage to an induction motor (CM) by pulse width modulation.

The CPU (40) receives an air-conditioning load signal such as an indoor temperature, and the speed control means (41)
The supply frequency of the induction motor (CM), which is the operating frequency of the compressor, is derived in response to the air conditioning load signal, and a control signal is output to the drive circuit (31) so as to reach the 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)
Will rotate in response to the air conditioning load.

During the rotation of the induction motor (CM), the optimal control means (42) makes the supply voltage of the induction motor (CM) minutely fluctuate by a predetermined fluctuation amount to minimize the motor current. 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.

On the other hand, while the induction motor (CM) is stopped, the CPU (40) may receive a preheating signal.
Specifically, between the time when the power supply (PS) is turned on and the time when the first air conditioning operation is started, or when the compressor is stopped,
In any state after 15 minutes or more and when the discharge pipe temperature T2 of the compressor becomes 7 ° C. or less, a preheating signal is output. That is, for example, when the outside air temperature is low,
Since there is a possibility that refrigerant may be mixed into the refrigerating machine oil of the compressor, the heat generation control means (43) receives the preheating signal and outputs a preheating control signal to the drive circuit (31). The drive circuit (31) receives this discharge control signal and controls ON / OFF of the six power transistors (Tr, Tr,...) Of the inverter circuit (23).

As shown in FIG. 3, of the supply voltage output from the inverter circuit (23) to the induction motor (CM), the V-phase supply voltage Sv is converted into a pulse-width modulated voltage by the induction motor (CM). CM), the U-phase supply voltage Su and the W-phase supply voltage Sw are square-wave AC corresponding to the supply frequency of the cycle, and are continuous voltages of a predetermined voltage that is not pulse width modulated. Output to induction motor (CM).

As a result, the induction motor (CM) itself generates heat and heats the refrigeration oil without the rotation of the induction motor (CM). The output of the preheating signal is stopped when either a temperature control operation start command (thermo-on command) is output or the discharge pipe temperature T2 of the compressor is higher than 9.5 ° C., or any of the conditions is satisfied. Therefore, the preheating control signal of the heat generation control means (43) is stopped and the induction motor (C
M) will stop the heat generation operation.

-Retry Control Operation- Next, a retry control operation when an overcurrent flows, which is a feature of the present invention, will be described with reference to a PAD flowchart shown in FIG.

First, when the control operation is started, step ST
In step 1, it is determined whether the state is "remote control stopped" and "motor is not being preheated". In other words, when the air conditioning operation is stopped, but the preheating by the heat generation control means (43) is not being performed, it is not necessary to execute the overcurrent retry control by the present control. (OC flag) is cleared, and the process proceeds to step ST3.
The retry timer is cleared, the process proceeds to step ST4, the retry counter is cleared, and the process proceeds to step ST5.

On the other hand, if the air-conditioning operation is stopped and preheating is being performed by the heat generation control means (43), the process proceeds from step ST1 to step ST5 to determine whether or not the retry timer has counted up. If the retry timer has counted up, the process proceeds to step ST6, where the retry counter is cleared.

If the retry counter in step ST6 has been cleared, and if the retry timer in step ST5 has not counted up, the process proceeds to step ST7.
It is determined whether an overcurrent has occurred. If no overcurrent has occurred, this routine is terminated and the operation from step ST1 is performed again.

On the other hand, if an overcurrent has occurred in step ST7, the determination is YES and the process moves to step ST8, where it is determined whether or not the retry timer is stopped. Then, the process proceeds to step ST9, the retry timer is started, this routine is terminated, and the operation from step ST1 is performed again. That is, during the preheating of the induction motor (CM) by the heat generation control means (43), if the current signal from the current transformer (CT) is received and the first overcurrent detection is performed, the retry timer is started, After temporarily interrupting the preheating operation by the heat generation control means (43), the retry means (44) causes the preheating operation to be retried.

Thereafter, the heat generation control means (43) resumes the preheating operation by the retry means (44),
In ST7 and ST8, if an overcurrent occurs within the predetermined time counted by the retry timer, the process proceeds from step ST7 and step ST8 to step ST10, increments the retry counter by 1, and proceeds to step ST11. It is determined whether or not has counted up to the specified number of times. Until the specified number of times is reached, this routine is terminated and the operation from step ST1 is performed again.

When the second overcurrent is detected, the preheating operation by the heat generation control means (43) is temporarily interrupted, and then the retry means (44) retry the preheating operation, and the above operation is repeated. Will repeat. afterwards,
When the number of retries performed by the retry means (44) reaches the specified number of times, the determination in step ST becomes YES and the process proceeds to step ST12, where the retry limit means (45) determines an overcurrent abnormality and sets the overcurrent flag. Then, this routine ends. That is, for example, if an overcurrent is detected even after performing four retries, it is considered that an original abnormality such as a short circuit has occurred instead of a transient overcurrent.
End the preheating operation.

-Effects of this embodiment- As described above, according to this embodiment, the induction motor (CM)
When an overcurrent is detected during the preheating of the power conversion circuit (20), the preheating operation is retried up to a predetermined number of times, and when the predetermined number of times is reached, the preheating control is terminated. ) Can be reliably prevented from stressing devices,
Destruction of these devices can be reliably prevented.

Further, since the induction motor (CM) is energized to generate heat, the induction motor (CM) itself also serves as a heater, so that the conventional crankcase heater can be omitted. The score can be reduced.

Further, in the case of the compressor of the air conditioner, since the refrigerant can be reliably prevented from being mixed into the refrigerating machine oil, the compressor can be smoothly started.

[0055]

In another embodiment of the present invention, the heat generation control means (43) converts a continuous voltage, which is not pulse width modulated, into a pulse width-modulated voltage for one phase and a pulse width modulated voltage for the other two phases. Although the wave AC is used, the present invention is not limited to these supply voltages, but in short, an induction motor (CM)
Any material that generates heat can be used.

In this embodiment, the induction motor (CM) of the compressor of the air conditioner has been described. However, the invention of claim 1 can be applied to various types of induction motors (CM). Further, the present invention is not limited to an induction motor (CM).

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

[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 waveform diagram showing a supply voltage waveform when the induction motor is preheated.

FIG. 4 is a control flowchart showing a retry control operation.

[Explanation of symbols]

 20 Power conversion circuit 21 Rectifier circuit 22 Smoothing circuit 23 Inverter circuit 30 Power control circuit 31 Drive circuit 40 CPU 41 Speed control means 43 Heating control means 44 Retry means 45 Retry control means PS power supply CM induction motor

Continuation of front page (56) References JP-A-62-33242 (JP, A) JP-A-1-57056 (JP, A) JP-A-1-270720 (JP, A) JP-A-3-65017 (JP) JP-A-5-26172 (JP, A) JP-A-7-19613 (JP, A) JP-A-7-167504 (JP, A) JP-A-7-285323 (JP, A) 8-9548 (JP, A) JP-A-9-79669 (JP, A) JP-A-9-149547 (JP, A) JP-A-63-70225 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F25B 1/00 H02H 7/06-7/097

Claims (2)

(57) [Claims] An electric power which includes a power supply (PS) and a motor (CM), and converts power supplied from the power supply (PS) into a predetermined controlled three-phase AC power and outputs the power to the motor (CM). A conversion circuit (20); a drive circuit (31) for outputting a drive signal to the power conversion circuit (20); and a control signal for controlling a supply frequency of the motor (CM). Speed control means (41) for outputting a control signal for variable speed control of the motor (CM) by pulse width modulation of the voltage to the drive circuit (31); and overcurrent detection for detecting an overcurrent flowing in the motor (CM) Means (CT), and a preheating control signal that receives a preheating signal during stoppage of the motor (CM) so as to energize the motor (CM) and generate heat when the motor (CM) is stopped. Heat generation control means (43) for outputting to the heat generation control means (43); If the overcurrent detection means (CT) detects an overcurrent during the preheating of the CM), the reheating means (44) for temporarily interrupting the preheating operation by the heat generation control means (43) and then retrying the preheating operation; When the number of retries of the retry means (44) reaches a predetermined number during the preheating of the electric motor (CM) by the control means (43), the retry limit means (45) which outputs an end signal for ending the preheating control to the heat generation control means (43). And a control device for the electric motor. 2. The motor control device according to claim 1, wherein the motor (CM) is a motor of a compressor provided in the air conditioner.