JPH0258871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a motor control device, and particularly to a motor control device that reduces a current limit value during regenerative operation.

[Technical background of the invention and its problems]

FIG. 1 is a block diagram of a general electric motor control device.

Speed reference signal 1 and speed feedback signal 2
is input to the speed control circuit 3, voltage control calculation is performed, and a current reference signal 4 is output. An alternator 5 detects the current flowing through the AC main circuit in accordance with the current flowing through the DC motor 13, and inputs the detected current to a current detection circuit 6 to detect a current feedback signal 7. the current reference signal 4 and the current feedback signal 7
is input to the minor current control circuit 8, current control calculation is performed, and the phase control signal 9 is output to the phase control circuit 10. The phase control circuit 10 performs phase control calculation and applies a gate pulse 1 to the thyristor 12A or 12B selected by the switching logic circuit 22.
Outputs 1A or 11B. As a result, a DC voltage is applied to the armature of the DC motor 13. Furthermore, apart from this, the field 14 of the DC motor 13 is excited by a DC power supply 15, and the DC motor 1
3 rotates. The rotation of the DC motor 13 produces a speed feedback signal 2 via a rotation detector 16 and a speed detection circuit 17.

In the above configuration, the current flowing through the DC motor 13 has a value proportional to the current reference signal 4. On the other hand, the DC motor 13 has an overcurrent rating, and a current limiting circuit is provided in the speed control circuit to prevent a current exceeding this rating from flowing, and the current is limited to the current reference signal 4 to prevent a current exceeding a predetermined value from flowing. has been established.

FIG. 2 shows an example of a conventional speed control circuit 3. As shown in FIG.
A speed reference signal 1 and a speed feedback signal 2 are input to a speed control circuit 3. The signal is connected to resistor 1
The current reference signal 4 is input to the operational amplifier 19 via 8A and 18B, and the difference between the two is outputted as a current reference signal 4 by a proportional-integral circuit comprising a resistor 18C and a capacitor 20. On the other hand, Zener diodes 21A and 21B are added to limit the current reference signal 4, and the positive voltage of the current reference signal 4, which corresponds to a negative current, is limited by the Zener diode 21B. The negative voltage of the corresponding current reference signal 4 is limited by the Zener diode 21A.

In this way, in the conventional motor control device,
It had a current limit depending on the overcurrent rating of the motor. Furthermore, when the capacity of the control rectifier is different for positive current and negative current, the current limit value is set to a different value for positive current and negative current to limit the current flowing through the control rectifier.

However, in a converter using a thyristor, there is a commutation overlap angle determined by the main circuit constant and the magnitude of the current, and when a large regenerative current is passed, the commutation overlap angle becomes large and there is a problem that commutation fails.

[Purpose of the invention]

The present invention has been made in view of the above problems, and
A regenerative current limiting circuit that is different from the normal current limiting value is provided, and this circuit is activated by a signal during regenerative operation to limit the magnitude of the current and prevent the overlap angle from becoming excessive during regenerative operation. It is an object of the present invention to provide a motor control device that prevents commutation failure.

[Summary of the invention]

In order to achieve the above object, the present invention includes a control circuit that controls either the speed or the voltage of the electric motor;
In a motor control device including a current control circuit that controls the current of the motor according to an output signal of the control circuit, a regeneration system that detects regenerative operation from a detection signal of either speed or voltage of the motor and a current detection signal. A regenerative operation detection circuit and a regenerative current limiting circuit that limits the output signal of the control circuit based on the detection signal of the regenerative operation detection circuit are provided to limit the current during regenerative operation to prevent an increase in commutation overlap angle and prevent commutation failure. This is a motor control device designed to prevent this from happening.

[Embodiments of the invention]

FIG. 3 shows the configuration of a regenerative operation detection circuit 29 used in the motor control device of the present invention and a speed control circuit 3 to which a regeneration current limiting circuit is added. The rest of the configuration is the same as in FIG. 1.

The output signal 23 of the forward/reverse switching logic circuit 22 is a logic signal that becomes "1" when the current is positive and becomes "0" when the current is negative, and is input to the regeneration detection circuit 29. Further, a speed feedback signal 2 which becomes a positive voltage when the DC motor 13 is rotating in the forward direction and a negative voltage when the DC motor 13 is rotating in the reverse direction is inputted to the regeneration detection circuit 29.

Next, the configuration of the regeneration detection circuit 29 will be explained. The speed feedback signal 2 is input to a comparator 24, which outputs a logic signal 23A which becomes "1" during reverse rotation and "0" during forward rotation. The logic signal 23 and the logic signal 23A are input to the AND circuit 25A, and are set to "1" during reverse regenerative operation, and "0" at other times.
A logic signal 23B is output. In addition, the logic signals 23 and 23A are connected to the knot circuit 26A,
The AND circuit 25B outputs a logic signal 23C which is input to the AND circuit 25B through the AND circuit 26B and becomes "1" during normal rotation regenerative operation and "0" otherwise.

The speed control circuit 3 and Zener diodes 21A and 21B in FIG. 3 are the same as those described in the conventional embodiment.

The FET 30A turns on when the logic signal 23B for detecting the reverse regenerative operation is "1" and becomes "0".
Turns off when. Further, the FET 30B is turned on when the logic signal 23C for detecting the normal rotation regenerative operation is "1" and turned off when it is "0". FET30
The circuits of A and 30B include Zener diode 21C,
21D and diodes 31A and 31B are provided.

The input signal 23 of the AND circuit 25A is a logic signal that becomes "1" when the current is positive, and the other input signal 23A becomes "1" when the DC motor 13 reverses.
A logic signal 23B is output which becomes "1" when there is a reverse positive current. This state of reverse positive current indicates reverse regenerative operation.

The input of the AND circuit 25B is a logic signal obtained by inverting the logic signal input to the AND circuit 25A, and outputs a logic signal 23C which becomes "1" when the current is positive or negative. This state of forward rotation negative current indicates forward rotation regenerative operation.

If the zener voltage of the zener diode 21C is set to a predetermined value lower than the zener voltage of the zener diode 21A, when the logic signal 23B becomes "1", the FET 30A is turned on, and the negative voltage limit of the current reference signal 4 is set to zero. determined by the inner diode 21C. For this reason, during reverse regenerative operation, the current reference signal 4
The limit value of can be determined by the Zener diode 21C, and the magnitude of the positive current flowing through the DC motor 13 can be limited.

Similarly, if the zener voltage of the zener diode 21D is set to a predetermined value lower than the zener voltage of the zener diode 21B, when the logic signal 23C becomes "1", the FET 30B turns on, and the positive voltage of the current reference signal 4 The limit is determined by the Zener diode 21D. Therefore, during normal rotation regenerative operation, the limit value of the current reference signal 4 can be determined by the zener diode 21D, and the magnitude of the negative polarity current flowing through the DC motor 13 can be limited.

As mentioned above, since the current limit value during regenerative operation can be set independently, by setting it low, the commutation overlap angle during regenerative operation can be reduced, and the motor can be controlled without commutation failure. A device is obtained.

When using this control device in a rolling mill, etc.,
Even in forward/reverse rolling, the current in the power running state generally requires a large current because it requires rolling torque, but the current in the regenerative state is only the deceleration torque of the inertia of the electric motor. It may be smaller than that in the power running state, and there is no practical problem even if the current limit value is made small during regenerative operation.

[Other embodiments of the invention]

FIG. 4 shows a circuit diagram of another embodiment of the present invention.

Logic signal 23B indicating reverse regenerative operation and logic signal 23C indicating forward regenerative operation are input to OR circuit 25C to obtain logic signal 23D which becomes "1" during regenerative operation, when logic signal 23D is "1" Turn on FET30C to reduce the current limit value during regenerative operation.

Although the embodiments of the present invention have been described with reference to a limiting circuit using a Zener diode, the same effect can be obtained by using a known limiting circuit instead of a Zener diode. Further, although the regenerative operation detection circuit 29 has been described as a circuit that detects based on the motor speed and current, the same effect can be obtained with a circuit that detects based on voltage and current.

Furthermore, although the embodiments of the present invention have been explained using examples constructed using hardware circuits, the same effect can be obtained by constructing similar functions using software in digital control using a microcomputer or the like.

〔Effect of the invention〕

According to the present invention, regeneration is performed by a regeneration detection circuit that detects regeneration operation, and a regeneration current limiting circuit that limits a current reference signal, which is the output of the speed control circuit, to a predetermined value during regeneration operation using the output of the regeneration detection circuit. It is possible to provide a motor control device that suppresses the current limit value to a low value during operation, reduces the commutation overlap angle, and has improved operational reliability without commutation failure.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a general motor control device, Figure 2
The figure is a conventional configuration diagram of the speed control circuit 3 used in FIG. 1, FIG. 3 is a configuration diagram of the regenerative operation detection circuit and speed control circuit used in the motor control device of the present invention, and FIG. FIG. 3 is a configuration diagram of a speed control circuit according to another embodiment of the present invention. 3... Speed control circuit, 5... Current transformer, 6... Current detection circuit, 8... Current control circuit, 10... Phase control circuit, 12A, 12B... Thyristor circuit,
13...DC motor, 16...Rotation detector, 17
...Speed detection circuit, 18A to 18C...Resistor,
19... operational amplifier, 20... capacitor, 21
A~21D... Zener diode, 22... Forward/reverse switching circuit, 24... Comparator, 25A, 25
B...AND circuit, 25C...OR circuit, 26
A, 26B...Knot circuit, 29...Regenerative operation detection circuit, 30A, 30B...FET, 31A, 3
1B...diode.

Claims (1)

[Claims] 1. In a motor control device comprising a control circuit that controls either the speed or voltage of the motor, and a current control circuit that controls the current of the motor according to an output signal of this control circuit, A regenerative operation detection circuit that detects a regenerative operation from one of the detection signals and a current detection signal, and a regeneration current limiting circuit that limits the output signal of the control circuit based on the detection signal of the regenerative operation detection circuit. Electric motor control device.