JPH0581516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a control device for an elevator driven by an AC motor.

[Conventional technology]

There is a method that uses an induction motor as the motor that drives the elevator car, and controls the speed of the motor by supplying alternating current power with variable voltage and frequency.
Since the current contains harmonics, large vibrations and noise caused by torque ripple occur in the electric motor and the car, especially at low speeds (low frequencies), which greatly affects the ride comfort of the elevator. Since elevators place great emphasis on ride comfort, it is necessary to prevent such vibrations and noise as much as possible. Conventionally, elevators have relied on power filters or PWM control methods to remove harmonic components. It was on.

Furthermore, in order to obtain good operating characteristics over a wide speed range, conventional control has been performed to fix the slip within a predetermined slip frequency range that provides good efficiency and power factor.

[Problem that the invention seeks to solve]

However, in order to use a power filter to reduce the torque ripple of the motor to the point where it does not affect the ride quality of the elevator, a large capacity capacitor or reactor is required, and when the PWM control method is used, the carrier frequency must be increased considerably. In either case, there was a problem that the device was complicated and expensive, such as the need to increase the height.

Another method is to reduce torque ripple by increasing the slip and lowering the magnetic flux of the motor, but simply increasing the slip will increase the current value during acceleration and deceleration, and the power supply Equipment capacity, voltage. frequency converter capacity,
There are problems with overcurrent and an increase in disconnection capacity.

[Means for solving problems]

First, the present invention focuses on ride comfort in elevators, so the acceleration is low at the start of acceleration (at low speed), and the running loss of the elevator is also small, so the current value is small. We focused on the fact that even if the value increases slightly, it does not have a large effect on the power supply capacity, etc., which is almost determined by the maximum current during acceleration and deceleration. The invention is characterized in that it includes means for changing the speed or frequency of. That is, the slip compensation signal is added to the primary frequency command to the electric motor to increase the slip only when the elevator starts accelerating, immediately before stopping, and especially at low speeds when the vibration and noise of the electric motor become large.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of an AC elevator control device according to the present invention.

In the diagram, RST is a three-phase AC power supply, and 1 is the power supply RST.
2 is a converter that converts three-phase AC power into DC; 3 is a DC reactor that smoothes the output current of converter 2; 4
is an inverter that converts direct current into alternating current with variable voltage and variable frequency; 5 is a power filter composed of a capacitor to absorb harmonic components; 6 is an induction motor that drives the elevator; 7 is the rotational speed of induction motor 6 ( Detects the elevator speed) and outputs the speed signal 7.
8 is a speed command generator that generates a predetermined speed command signal 8a; 9 is an adder that outputs a deviation signal 9a between the speed command signal 8a and the speed signal 7a; 10 is a deviation signal 9a 11 is a slip setting device that outputs the output of the speed regulator 10 as a slip frequency signal 11a;
2 is a polarity discriminator that determines the polarity of the slip frequency signal 11a; 13 is a slip compensator that outputs a slip compensation signal 13a according to the speed of the elevator; 14;
1 is an adder that outputs the speed signal 7a and the slip frequency signal 11a plus a slip compensation signal 13a as a primary frequency command 14a; 15 is a V/F converter that converts a voltage signal into a frequency signal; 16 is a frequency signal 17 is a rectifier, 18 is an adder, 19 is a current regulator that controls the output current of converter 2, and 20 is a phase controller that controls the phase of converter 2. It is a vessel.

FIG. 2 is a diagram showing an embodiment of the characteristics of the slip compensator, in which the speed signal 7a and the primary frequency command 14a
It also shows the relationship between As is clear from the figure, the slip compensation signal 13a is at its maximum at the start of acceleration or at low speed just before stopping, and the current value is at its maximum near the end of acceleration or the start of deceleration, or when motor vibration and torque ripple affect ride comfort. It is set to zero at constant velocity, where there is almost no effect. Note that during deceleration, the polarity of the signal 11a changes depending on the load condition of the elevator, so the polarity is switched by a polarity discriminator accordingly.

As is clear from the above configuration, converter 2
The output current is the deviation signal 9 between the speed command and the actual speed.
Although it is controlled according to the value of a, a slip compensation signal as shown in FIG. 2 is further added to the primary frequency command 14a given to the inverter 4.
When the elevator speed is low, the electric motor is controlled so that the slip increases accordingly.

FIG. 3 is a diagram for explaining that as the slip increases, the torque ripple decreases. (a) shows the case where the slip is small, and (b) shows the case where the slip is large. In a current source inverter, the primary current is a square wave, but the magnetic flux is almost a sine wave due to delays in the magnetic and electric circuits of the motor. Therefore, during commutation, as shown in Figure 3,
The primary current vector I〓 instantly changes from a solid line to a dashed-dotted line with a phase difference of 60°, but the magnetic flux vector Φ〓 rotates at a nearly constant speed. As a result, the torque during commutation is calculated from KΦ〓Isinθ, where K is the motor constant, to KΦ〓Isin(θ
+60°), and this appears as torque ripple. Since K and Φ are constant here, the degree of change in the component contributing to the torque of the primary current from Isin θ to Isin (θ+60°) corresponds to the magnitude of the torque ripple.

On the other hand, as the slip increases, the primary current I increases, but as shown in Figure 3b, the primary current vector
The phase difference θ between I〓 and the magnetic flux vector Φ〓 also increases, and as a result, as is clear from the case of Fig. 3a, the change in the current component contributing to the torque, i.e.
The degree of change from Isin θ to Isin (θ + 60°) becomes smaller, and the torque ripple also becomes correspondingly smaller (however, θ≦60°).

〔Effect of the invention〕

According to the present invention, since the slip can be increased only when the elevator is at low speed, the vibration and noise caused by the torque ripple of the electric motor, which becomes large especially at low speed, can be reduced, and the ride comfort of the elevator can be improved.Moreover, the current value At the point when is at its maximum, the slip is as small as before, so there is no need to increase the power supply capacity. Furthermore, even when a power filter is used, the torque ripple is reduced, so a capacitor or reactor with a small capacity can be used.

Further, if further reduction in vibration, noise, and torque ripple of the electric motor is required, in addition to the above embodiment, it is also possible to easily implement a PWM control method when the elevator is running at low speed. In this case as well, the PWM control device has a smaller torque ripple than the conventional one, so the carrier frequency can be lower, and therefore it can be configured with a normal phase control thyristor instead of a high-speed switching thyristor. The structure can be simpler and cheaper than the device.

Although the above explanation has been made using a current source inverter as an example, similar effects can be obtained when a voltage source inverter is used.

It goes without saying that the present invention can also be applied to automatic leveling operation in which re-leveling is performed at a very low speed, and the slippage can be increased at any other speed (for example, the speed at which the car or rope system resonates).
It is also possible to reduce vibrations due to resonance.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of an AC elevator control device according to the present invention, Fig. 2 is a diagram showing an embodiment of the characteristics of a slip compensator, and Fig. 3 explains the relationship between slip and torque ripple. This is a diagram for 2...Converter, 3...DC reactor, 4
...Inverter, 5...Power filter, 6...
Induction motor, 7... Speed generator, 8... Speed command generator, 10... Speed regulator, 11... Slip setter, 12... Polarity discriminator, 13... Slip compensator, 15... V /F converter, 16...Pulse distributor.

Claims (1)

[Claims] 1 Convert commercial AC power to DC using a converter, convert this to variable frequency AC power using an inverter, drive an induction motor with this converted AC power, and adjust the set slip frequency and elevator The elevator speed control is performed according to the primary frequency command obtained by adding the feedback speed, and the elevator is equipped with a slip compensator that outputs a slip compensation signal only at low speeds just before the start of acceleration and stop of the elevator, and the slip compensation A control device for an AC elevator, characterized in that the control device for an AC elevator is configured to increase slip only at the low speed of the elevator by adding a signal to the primary frequency command.