JPS63144778A - Motor controller - Google Patents

Abstract

PURPOSE:To prevent rush current from flowing when the input of control signal is provided, by providing the passage of the speed command signal of input to a speed error amplifying section, with a switch to be switched with the control signal for controlling a power converting section. CONSTITUTION:When the non-input of control signal input (a) is provided, then an analog switch is put in a fallen state on the circuit ground side of a speed error amplifying section 1. Then, the speed command signal (j) of input of the speed error amplifying section 1 is set to be signal without offset. A motor 4 is in a stopping state, and so speed feedback signal (c) is zero, and speed error amplifying section output (d) is almost in a zero state. After that, when the input of the control signal input (a) is provided, then the analog switch 6 is put in a fallen state on the side of speed command signal input (b), and the input of the command signal (j) to the speed error amplifying section 1 is provided. In this case, the output (d) of the speed error amplifying section 1 is increased from the first state of zero on, and so rush current is prevented from flowing to the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor control device to which an analog speed command signal is applied.

BACKGROUND OF THE INVENTION In recent years, with the diversification of motor control, a method of configuring a speed feedback loop to improve speed controllability has become common. To control the speed, a speed command voltage is input from the outside, but depending on how this speed command is given, there are problems such as excessive current flowing to the motor at the moment the control signal that controls the power converter is input. .

The conventional motor control device as described above will be described below with reference to the drawings.

FIG. 4 is a block diagram of a conventional motor control device. In FIG. 4, 1 is a speed error amplification unit that amplifies the difference between an external speed command signal input (b) and a speed feedback signal (C) obtained by detecting the rotation speed of the motor 4 with a speed detector 5. ,
2 is a current command converter that converts the output of the speed error amplifier 1 into a current command signal that drives the motor 4; 3 is a switch for a power element that controls energization of the motor 4 using the output of the current command converter 2; This is a power converter that performs In addition,
(a) is a control signal input that controls the operation and non-operation of the power converter 3.

The operation of the motor control device configured as above will be described below.

The speed error amplifier 1 compares the speed command signal input (b) given from the outside with the speed feedback signal (e) obtained by detecting the rotation speed of the motor 4 with the speed detector 5, and amplifies the difference. and output it. The current command conversion section 2 receives the output (d) of the speed error amplification section 1 and converts this signal (d) into a command signal (e) for driving the motor 4. The power converter 3 switches the power element based on the output signal (e) of the current command converter 2, and supplies a current (f) for driving the motor 4. The control signal input (a) is given from the outside, and at the time of input, the output of the current command converter 2 is transmitted to the power converter 3,
The power element becomes operable and the motor 4 becomes controllable.

When the control signal input (a) is not input, the output (e) of the current command converter 2 is not transmitted to the power converter 3, the power element is in a non-operating state, and the motor 4 is in an uncontrolled state.

Problems to be Solved by the Invention In the above configuration, the control signal input (a) and the speed command signal input (b) must be input at the same time or the control signal input (a) must be input first. This is because the speed command signal input (b) is given as an analog quantity, so it is difficult to make the speed command value completely zero due to the impedance of the signal path, external noise, etc. As shown in Figure 5, An offset voltage (h) is usually present. However, since the amplification factor of the speed error amplification section 1 is usually quite large, even if there is a slight offset voltage input, the output of the speed error amplification section 1 (
d) reaches a considerable level as shown in Figure 5, and sometimes reaches a saturated state. Therefore, the output (e) of the current command converter 2 is also a command value that allows a considerable amount of current to flow. When the control signal (a) is input in such a state, an inrush current shown as motor current (f) flows through the motor 4, and depending on this current value, the motor 4 may be demagnetized or the overcurrent protection circuit may be activated. It had problems such as malfunction.

The present invention has been made in view of the above problems, and provides a motor control device that can prevent demagnetization of the motor and operation of an overcurrent protection circuit when a control signal is input.

Means for Solving the Problems To achieve this objective, the motor control device of the present invention comprises:
A switch that is opened and closed by a control signal that controls the power converter is provided in the path of the analog speed command signal that is input to the speed error amplifier.

Operation In the motor control device of the present invention, the speed command signal is not input until the control signal is input, so even if an offset voltage exists in the speed command, it does not affect the output of the speed error amplification section. First, no inrush current flows when a control signal is input (this prevents motor demagnetization and malfunction of the overcurrent protection circuit).

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a motor control device that is an embodiment of the present invention. In FIG. 1, 1 is a speed error amplification section, 2
is a current command converter, 3 is a power converter, 4 is a motor, 5
1 is a speed detector, (a) is a control signal input, (b) is a speed command signal input, and (C) is a speed feedback signal, which is the same as the configuration shown in FIG. 4. The difference is switch 6, which is a means for opening and closing the path for speed command signal input (b) in response to control signal input (a).

The operation of the motor control circuit configured as described above will be explained below using a specific example of this embodiment.

FIG. 2 shows a specific example of the switch 6 of this embodiment (
A) is a control command signal input, and (b) is a speed command signal input, which are the same as in FIG. 1. 6a is an analog switch, and U) is a speed command output signal.

First, when the control signal input (a) is not input, the analog switch 6a is tilted toward the circuit ground side of the speed error amplifying section 1, and as shown in the timing chart of FIG. b) with offset voltage (h
) exists, the sudden speed command signal U) input to the speed error amplification section 1 becomes a signal without offset. Since the motor 4 is in a stopped state, the speed feedback signal (C) is also zero, and the speed error amplifier power (d) is almost zero.

-6= Next, control signal input (a) at timing (i) in Figure 3
is input, the analog switch 6a falls to the speed command signal input (b) side, and the command signal (D) is input to the speed error amplification section 1. At the same time, the power conversion section 3 becomes operational and the speed error amplification section output (d ) flows through the motor 4, but since the output (d) of the speed error amplifier 1 increases from the initial zero state, the motor current (f) becomes as shown in FIG. Inrush current as shown in Figure 5 does not flow.

As described above, according to this embodiment, the speed command signal input (b
By providing a switch 6 that is opened and closed by the control signal (a) in the path of ), it is possible to prevent the output (d) of the speed error amplifier 1 from being saturated or close to it when the control signal (a) is not input. prevent motor current (f) from increasing when control signal (a) is input.
) can be prevented from becoming an inrush current.

Effects of the Invention As described above, the present invention provides a switch in the path of the speed command signal given as an analog quantity, and performs opening/closing control using a control signal that controls the power converter. It is possible to eliminate inrush current caused by signal offset voltage and prevent motor demagnetization and malfunction of the overcurrent protection circuit. Furthermore, the allowable value for the offset voltage of the speed command signal input is widened (possible).In this way, it is possible to increase the reliability of motor control more easily.
The effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of a switch according to an embodiment of the present invention, and FIG. 3 is an operation of an embodiment of the present invention. FIG. 4 is a block diagram of a conventional motor control device, and FIG. 5 is a timing chart showing the operation of the conventional motor control device. 1... Speed error amplification section, 2... Current command conversion section, 3... Power conversion section, 4...
・Motor, 5...Speed detector, 6...
Switch, 6a...Analog switch. Fig. 2 νte (3 n Fig. 3 (L) (a)-” -m- Cf) -su- Fig. 4 Fig. 5 (尤)

Claims (1)

[Claims] A speed error amplification section that compares an analog speed command signal with a speed feedback signal obtained by detecting the motor rotation speed with a speed detector, and converts the output of this speed error amplification section into a command signal that drives the motor. a power converter that switches a power element that controls energization of the motor using the output of the command converter, and a switch that controls input of the speed command signal using an external signal. Motor control device.