JPH04105579A - Method for starting electric motor - Google Patents

Abstract

PURPOSE:To smoothly start an electric motor by starting the electric motor by torque control at the time of starting the electric motor, and then switching the torque control to the speed control. CONSTITUTION:A speed governor 3 is saturated by turning on a switch 8A to give a torque limit signal tauFMAX to a limiter 4 through an acceleration/ deceleration arithmetic device 7 thereafter turning on a switch 8B to input a speed governor saturating speed command value N to the speed governor 3. The torque limit signal tauFMAX is increased at a fixed slope by the acceleration/deceleration arithmetic device 7 to reach a torque limit value tauFMAX. Next, when a torque command value tau, which is an output of the limiter 4, agrees with load torque tauL, an electric motor is started. When a speed actual value Nist is increased by the torque command value tau to agree with the speed command value N, after the electric motor is started, a switch 8C is turned on to release saturation of the speed governor 3. Then, speed control, based on a shockless speed command generator 5, is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for starting an electric motor, and particularly to a method for starting an electric motor whose load torque at startup is not constant.

[Conventional technology]

FIG. 3 is a block diagram for explaining a conventional example of a motor control method. In the figure, 1 is an electric motor, 2 is a torque regulator (ATR), 3 is a speed regulator (ASR), and 4
5 is a shockless speed command generator, 6 is a speed setter, and τ and □ are torque limit values. Note that here, the motor 1 includes an armature circuit 11 and a field element 12.
A, 12B and an integral element 13 are illustrated.

That is, the shockless speed command generator 5 is composed of, for example, a function generator, and the speed setting value Nst from the speed setting device 6 is
The speed regulator 3 executes speed control by performing a predetermined control calculation to make the actual speed value N15t obtained via the electric motor 1 coincide with the speed command value N0. . Note that the output from the speed regulator 3 and the torque limit value τ□□ are introduced into the limiter 4, and since the limiter 4 selects and outputs the smaller of these inputs, the speed is adjusted. If the output from the device 3 becomes too large, it will be limited to the torque limit value rFMAX.

FIG. 4 shows the relationship between the speed setting value Ns t, the speed command value N'' and the acceleration/deceleration N8 for the shockless speed command generator 5. As is clear from FIG. In order to keep the acceleration/deceleration change rate constant at the inflection points (start of acceleration, completion of acceleration, start of deceleration, completion of deceleration),
It can be seen that the speed command value N1 as shown in (b) of the same figure is output for the speed setting value as shown in (a).

[Problem to be solved by the invention]

In such a configuration, the load torque τ becomes the input to the integral element 13 in FIG. 3 when starting the electric @I.

is relatively large, the motor is not started until the motor generated torque τ8 exceeds the load torque τ, and therefore the deviation between the speed command value N'' and the actual speed value N15t becomes large.After that, the motor generated torque τ, Starting is started when the load torque τ exceeds the load torque τ, and rapid acceleration is performed to reduce the speed deviation to 0, which causes problems such as overshoot and failure to perform good control.

Therefore, an object of the present invention is to smoothly perform control at the time of startup.

[Means to solve the problem]

In order to solve such problems, the present invention includes a regulator in the minor loop that performs a torque adjustment operation to make the torque of the electric motor match a target value, and a regulator outside of the regulator to make the motor speed match the target value. A motor control device having a speed regulator as a major loop that performs a speed adjustment operation is characterized in that when starting the motor, the motor is started by torque control and then switched to speed control.

[Effect]

While the speed regulator is saturated when starting the motor, the torque limit is released at a constant slope (i.e., the motor is started with torque control based on the torque command value), and the speed command value is changed after starting is completed. Performs speed control based on In other words, we focused on the fact that it is impossible to estimate the torque at the time of starting the electric motor, so we increase the motor torque at a constant slope (increase the acceleration torque at a constant slope), and when this exceeds the load torque, the speed command is By starting speed control based on the value, smooth startup of the electric motor is possible.

〔Example〕

Next, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part for explaining its operation.The following description will be made with reference to these figures.

That is, in this embodiment, when starting the electric motor 1, first the switch 8A is turned on and the torque limit signal τ□□
is given to the limiter 4 via the acceleration/deceleration calculator 7, and then the switch 8B is turned on to obtain the speed command value Δ for saturation of the speed regulator.
By inputting N into the speed regulator 3, the speed regulator 3
saturate.

The torque limit signal τFNAX is output to the second
The torque increases at a constant slope (acceleration/deceleration change rate b) as shown in Figure (b), and eventually reaches the torque limit value τ□l. When the torque command value τ, which is the output of the limiter 4, matches the load torque τ, the electric motor starts (see FIG. 2(c)). After starting, the actual speed value N15t increases according to the torque command value τ as shown in FIG.

That is, as the speed regulator 3, a non-saturated type PI (proportional integral) calculator is used which changes the output according to a change in the input even if it is saturated. Thereafter, speed control based on the shockless speed command generator 5 is started in the same manner as before.

In this way, the torque control allows for a shockless start with a constant acceleration/deceleration change rate up to the speed command value ΔN, so it is possible to start even if the load torque τ1 is not constant, and the shockless speed command Since the torque command has the same acceleration/deceleration rate of change as the generator 5, not only is shockless starting possible, but at speeds above ΔN, the acceleration α and acceleration/deceleration rate of change from the shockless speed command generator 5 are Based on the speed command, normal control is possible.

(Effects of the Invention) According to the present invention, when the electric motor is started, a circuit is added to sequentially increase the torque limit value at a constant slope, and the electric motor is started by torque control, and after the start is completed, the electric motor is switched to speed control. Therefore, even if the load torque is large or the motor load is not constant, smooth starting can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the present invention in detail, Fig. 2 is a waveform diagram of each part for explaining its operation, Fig. 3 is a block diagram for explaining the conventional example, and Part 4 is the same. It is a waveform diagram of each part for explaining operation. DESCRIPTION OF SYMBOLS 1... Electric motor, 2... Torque adjuster, 3... Speed moderator, 4... Limiter, 5... Shonless speed command generator, 6... Speed setter, 7 ...Acceleration/deceleration calculator, 8A. 8B, 8C...switch. 11... Armature circuit, 1
2A, 12B... Field element, 13... Integral element.

Claims (1)

[Scope of Claims] 1) A regulator that performs a torque adjustment operation to make the torque of the electric motor match a target value is provided in the minor loop, and a speed adjustment device that performs a speed adjustment operation to make the motor speed match the target value outside the minor loop. 1. A method for starting an electric motor in an electric motor control device having a loop including a regulator as a major loop, characterized in that when starting the electric motor, the electric motor is started by torque control and then switched to speed control.