JPH06106035B2 - Torque limiting method for voltage type variable voltage variable frequency inverter device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque limiting method for a voltage type variable voltage variable frequency inverter device that performs vector control of an electric motor but does not have a power regeneration function.

[Prior art and its problems]

In this type of torque limiting method, when the electric motor is started, it is promptly determined whether the operation is in the power running mode or the regenerative mode, and when it is in the power running mode, the motor is always operated at the maximum allowable torque of the inverter device. Be able to start.

Generally, in a voltage type variable voltage variable frequency inverter device that does not have a power regeneration function, when the operation of the AC motor driven by the inverter device is in a regeneration mode, a value that can be consumed inside the inverter device When the power exceeding the above value is regenerated, the voltage of the DC intermediate circuit section is pushed up, resulting in overvoltage, and in the worst case, the operation of the inverter device must be stopped. It is important to suppress the regenerative power of the electric motor to a safe level for the inverter device via the.

Conventionally known as this type of torque limiting method is to determine whether the operation of the electric motor is in the power running mode or the regenerative mode, and to perform the torque limitation when it is determined to be in the regenerative mode. Is. However, in this type of torque limiting method, when the electric motor is started, at the time when the electric motor has not started to rotate yet, the speed feedback cannot be obtained from the speed signal output means such as the pulse transmitter, so that the rotation direction cannot be obtained. However, even if the electric motor is started, the torque limiting means works as if the judgment based on the torque polarity is erroneous and the operation is in the regenerative mode, and the torque of the inverter device is reduced. As a result, there is a disadvantage that the starting torque is insufficient and the electric motor cannot be started.

In this case, in the torque limiting method, there is one in which the torque limiting value in the regenerative mode is increased as much as possible in order to facilitate starting of the electric motor to some extent. Since the starting torque cannot be increased at will because there is a limit to the power that can be consumed, it is still impossible to start when the starting torque required for the electric motor is large, and the output of the inverter device The drawback is that the torque available is insufficient for starting the motor.

[Object of the Invention]

In view of the above-mentioned drawbacks of the torque limiting method of the variable voltage variable frequency inverter device that performs conventional vector control but does not have the power regeneration function, is the operation in the power running mode in a short time when starting the electric motor? Provided is a torque limiting method for the inverter device having a simple circuit configuration in which it is determined whether the regenerative mode is set, and when the power running mode is set, the electric motor is always started with the maximum torque that can be output by the inverter device. The purpose is to do.

[Main points of the invention]

In order to achieve the above-mentioned object, in the present invention, in the torque limiting method described above, a power running regenerative mode judging means for judging whether it is a power running mode or a regenerative mode from the rotation direction and torque polarity of the electric motor, and the electric motor. A motor zero speed detecting means for detecting the presence / absence of speed is provided, and at the time of starting the electric motor, the power running regeneration mode judging means judges that the mode is a regeneration mode and the zero motor speed detecting means detects that there is a motor speed. In this case, the torque limit value in the regenerative mode is selected as the absolute torque command value of the inverter device so that the power running regenerative mode determination is performed when the electric motor zero speed detecting means detects zero speed. The torque limit value in the powering mode is always selected as the absolute torque command value of the inverter regardless of the determination of the means. Motivated is intended to be as to start by the maximum starting torque.

Example of Invention

Next, the details of the present invention will be explained based on the embodiments shown in the drawings.

In the circuit shown in FIG. 1, the rotation direction signal 6 of the electric motor and the torque polarity signal 7 of the electric motor obtained from the speed regulator are input to the power running regeneration mode discrimination means 8 of the electric motor, and the output signal 9 thereof has an AND circuit. In addition to being input to the logic 12, the speed detection signal 11 obtained from the motor zero speed detecting means 10 including the speed generator of the motor and the comparator is also input to the logic 12. The torque limit value switching switch 5 is operated by the output signal 13 of the logic 12 to select either the power running mode torque limit value or the regenerative mode torque limit value, and the selected torque limit value signal 14 is sent to the torque limiting means 2. The absolute value 1 of the torque command given to the inverter device is limited to the selected torque limit value.

At that time, since there is a relationship between the rotation direction of the electric motor and the torque polarity as shown in FIG.
Based on the rotation direction signal 6 and the torque polarity signal 7 inputted to the above, the signal 9 discriminated and outputted by the mode discriminating means 8 is a logic 0 signal when the powering mode is present and a logic 1 signal when the mode 9 is in the regeneration mode. And meanwhile, motor zero speed detection means
Logic 12 is a logic 0 signal when the detection signal 11 of 10 is zero motor speed, and logic 1 signal when there is a motor speed.
When the operation of the electric motor is in the powering mode (logic 0 signal), whether the detection signal 11 of the speed zero detection means 10 is the motor speed zero (logic 0 signal) or the motor speed exists (logic 1 signal). In either case, the output signal 13 of the logic 12 becomes a logic 0 signal so that the torque limit value switching switch 5 always selects the power running torque limit value 3.

Next, when the operation of the electric motor is in the regeneration mode (logic 1 signal), when the detection signal 11 of the speed zero detection means 10 is the electric motor speed zero (logic 0 signal), the output signal 13 of the logic 12 is output.
Becomes a logic 0 signal and the torque limit value switching switch 5 selects the torque limit value 3 during power running as in the above. However, only when the detection signal 11 of the speed zero detecting means 10 has a speed (logic 1 signal), Since the output signal 13 of 12 becomes the logic 1 signal, the torque limit value switching switch 5 selects the regeneration torque limit value 4.

When the electric motor is started in the torque limiting circuit of the variable voltage variable frequency inverter device according to the present invention, the electric motor speed zero detecting means 10 detects whether the electric power running regeneration mode judging means 8 is in the power running mode or the regeneration mode. When the detected signal is the electric motor speed zero, the torque limit value switching switch 5 always selects the power running torque limit value 3, so that the electric motor can be started with the maximum torque that the inverter device can output. However, after the electric motor is once started, its speed reaches the detectable range of the electric motor speed zero detecting means 10, the zero speed detecting means 10 detects the existence of the electric motor speed, and the judgment of the mode judging means 8 is in the regenerative mode. Only in a certain case, the torque limit value switching switch 5 is switched to select the regenerative torque limit value 4. Therefore, the torque limiting means 2 adjusts the torque of the electric motor so that the regenerative electric power can be accepted by the inverter device. Will be suppressed.

〔The invention's effect〕

As described above, the present invention, in the torque limiting method of the voltage source variable voltage variable frequency inverter device that performs vector control of the electric motor but does not have the power regeneration function, in the power running mode from the rotation direction and the torque polarity of the electric motor. There is provided a circuit composed of a power running regeneration mode determining means for determining whether there is a certain speed or a regeneration mode and a motor speed zero detecting means for detecting the presence or absence of the speed of the electric motor, and when the electric motor is started, the power running regeneration mode determining means determines Is in the regenerative mode and the motor speed zero detection means detects that the motor speed is present, by selecting the torque limit value in the regenerative mode as the torque command absolute value of the inverter device, Since the torque limit value during power running is always selected near zero speed, whether the motor is in power running mode when starting. Even if there is an error in determining whether the mode is the raw mode, the electric motor is started with the maximum torque that can be output by the inverter device regardless of the error. Therefore, there is no fear of the electric motor starting failure due to insufficient starting torque. effective.

[Brief description of drawings]

FIG. 1 shows an embodiment of a circuit of a torque limiting system of a voltage type variable voltage variable frequency inverter device according to the present invention, and FIG. 2 shows a diagram showing a relationship between a rotating direction of an AC motor and a torque polarity. . 1 ... Absolute torque command value, 2 ... Torque limiter, 3 ... Power running mode torque limit value, 4 ... Regenerative mode torque limit value, 5
... torque limit value switching switch, 8 ... power running regeneration mode discrimination means, 10 ... electric motor speed zero detection means, 12 ... logic.

Claims (1)

[Claims] 1. A torque limiting method for a voltage-type variable voltage variable frequency inverter device that performs vector control of an electric motor but does not have a power regeneration function, in a power running mode or a regenerative mode depending on the rotation direction and torque polarity of the electric motor. A circuit comprising a power running regeneration mode determining means for determining whether or not and a motor speed zero detecting means for detecting the presence / absence of speed of the electric motor is provided, and when the electric motor is started, the determination of the power running regeneration mode determining means is in the regenerative mode. Yes, and only when the zero motor speed detecting means detects that there is a motor speed,
A torque limiting method for a voltage-type variable voltage variable frequency inverter device, wherein a torque limiting value in a regenerative mode is selected as a torque command absolute value of the inverter device.