JPS6253435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for an AC elevator controlled by an inverter.

[Prior art]

Conventionally, in AC elevators driven by three-phase induction motors, power running torque is increased by controlling the primary voltage of the induction motor during acceleration, and DC braking torque is increased by controlling the DC current supplied to the primary winding of the induction motor during deceleration. Each adopted a speed feedback control method.

This method has the problem that the induction motor is controlled within a range of large slip during both acceleration and deceleration, resulting in large rotor loss and increased power consumption.

As a means of solving this problem, if the speed of the elevator is controlled by changing the frequency of the voltage applied to the induction motor, the induction motor can be controlled within a range with small slippage and efficient operation can be achieved.

Although this inverter system has the above-mentioned characteristics,
On the other hand, it was found that the following new problems were encountered, which did not need to be considered in the conventional primary voltage control method.

(1) During regenerative operation, if the inverter frequency suddenly decreases, overvoltage will occur.

(2) If an AC power outage occurs during regeneration in an inverter capable of power regeneration, an overcurrent will flow.

Therefore, if left as is, there is a risk of damage to the elements of the inverter device, burnout of the motor, etc.

[Purpose of the invention]

An object of the present invention is to provide a control device for an AC elevator that can prevent accidents such as damage or burnout to the inverter device, electric motor, etc. in the event of the above-mentioned abnormality, and can restart the operation of the elevator. .

[Summary of the invention]

A feature of the present invention is that the inverter current, voltage, AC power supply current, elevator speed, etc. are monitored, and in the event of an abnormality, the inverter is forcibly stopped and then the power is cut off. Furthermore, after the inverter is stopped, a mechanical brake is applied to stop and hold the elevator.

[Embodiments of the invention]

As is well known, the inverter needs to perform V/constant control so that the voltage V applied to the induction motor and the frequency have the relationship shown in FIG.

Therefore, in order to make the output voltage of the inverter proportional to its frequency and have the relationship shown in Figure 1, since the period is long in the low frequency region, half a cycle is required as shown in Figure 2. Increase the number of pulses N in between, and increase the conduction rate Tp/T(T
is the time between half cycles, and Tp is the pulse width). On the other hand, in the high frequency region, the period is short, so the number of pulses N is reduced as shown in Figure 3, and the pulse conductivity Tp/
Control T to be large. This is called pulse width modulation control (PWM control), and if the voltage applied to the induction motor is controlled using this method, the torque characteristics will be as shown in Figure 4.

The present invention uses this characteristic to control the speed of the elevator. Hereinafter, one embodiment of the present invention will be described in detail using FIG. 5.

In FIG. 5, under normal conditions, the main circuit contactor 23 is closed, and the converter 2 converts the three-phase AC voltage into a DC voltage, which is supplied as a DC power source to the inverter 3.

_The converter 2 and the inverter 3 are well-known circuits as shown in _FIG . The voltage is smoothed by a capacitor 24 and becomes the DC voltage of the inverter 3.

This voltage is converted into three-phase alternating current by an inverter 3 made up of transistors Tr ₁ to _{Tr 6} , and as shown in FIG. 1, the torque of the induction motor is controlled by controlling the frequency while keeping the ratio of voltage to frequency constant.

Note that the diodes D ₁ to _{D 6} of the inverter 3 are freewheeling diodes that charge the capacitor C with the induced voltage of the induction motor during regeneration, and the transistors Tr ₇ to _{Tr 12} of the converter 2 are arranged so that the voltage of the capacitor 24 is higher than that of the AC power supply 1. When the voltage becomes high, the transistors Tr ₇ to _{Tr 12} are controlled to be conductive in accordance with the phase of the AC power source 1, and the regenerative power of the motor 5 is returned to the AC power source 1.

Overcurrent of this converter 2 and inverter 3,
As a protection device against overvoltage, the overcurrent detection device 25 of the AC power supply, the overcurrent detection device 26 of the converter 2, the DC overvoltage detection device 27, the overcurrent detection device 28 of the inverter 3, and the outputs of these devices are collectively processed and installed in the converter. , inverter overcurrent,
An overcurrent/overvoltage detection signal generator 29 is provided that generates a signal indicating overvoltage.

First, a case will be described in which the acceleration and deceleration of an elevator is performed using such a converter and inverter.

When the sequence controller 22 generates an elevator operation start signal, the electromagnetic brake 5 is released, and the speed command device 13 generates a speed command that increases as time increases.

The comparator 14 detects the difference between this speed command signal and the speed signal from the speed detection generator 12 connected to the three-phase induction motor 4 for driving the elevator, and uses this to generate a pulse for generating the PWM control pulse. input into the device 15;

This pulse generator 15 adjusts the number of pulses and the conduction rate to the speed command and the speed in order to control the transistor shown in FIG. 6 so that the ratio of the voltage and frequency applied to the induction motor 4 is constant. It is configured to output a pulse according to the difference between the signal and the signal.

The number of pulses is increased in the low frequency region to suppress low-order harmonics, suppress current ripple, and improve the drive characteristics of the motor.
On the other hand, in a high frequency region, the number of pulses is set to be small due to the limit of switching time of the main circuit transistor.

The output of this pulse generator 15 is amplified to a predetermined value by a pulse amplifier 16, and this is applied to the base of the transistor of the inverter 3, and the frequency is gradually increased according to the speed control deviation to increase the power running torque of the motor 4. The elevator car 9 and counterweight 10 are accelerated and controlled via the reducer 6, sheave 7, and rope 8.

With this method, when the elevator accelerates and travels a predetermined distance and reaches a certain position before the landing point, the position detector 11 installed on the car detects the position from this position to the landing point. , this is input to the speed command device 13.

The speed command device 13 generates a speed command that decreases according to the deceleration position of the elevator, and according to the difference between this and the speed signal, the pulse generator 15 controls the speed control while keeping the voltage/frequency constant. The regenerative braking torque of the induction motor 4 is controlled by gradually decreasing the frequency in accordance with this, thereby controlling the deceleration of the elevator.

In order to return the regenerated power during deceleration to the power source, the DC voltage of the inverter 3 (the voltage of the capacitor C in FIG. 6) is detected by the voltage detection device 21, and the difference between this and the output of the reference value generator 17 is compared. The output of the voltage detection device 21 is detected by the reference value generator 1
7, the pulse generator 19 generates a pulse for PWM control of the transistors Tr ₇ to _{Tr 12} of the converter 2 according to the difference. Then, this is amplified to a predetermined value by the pulse amplifying device 20, and the transistor is controlled to be conductive, so that the regenerative power of the induction motor 5 is returned to the AC power source 1.

By the method described above, when the elevator decelerates and reaches the landing point, this (elevator car 9
(information on the position of the elevator, the speed of the elevator, etc.) is input to the sequence controller 22, and a stop signal output from the sequence controller 22 activates the electromagnetic brake 5 to stop and hold the elevator.

In such a system, if overcurrent or overvoltage occurs due to an abnormality such as a sudden decrease in the inverter frequency or a power outage of the AC power supply as described above, this is detected by the overcurrent detection devices 25, 26, 28 and the overvoltage detection device 2.
7, input this to the overcurrent/overvoltage detection device, and send the output signal to the sequence controller 2.
2 and immediately switch to sequence controller 2.
2 generates a signal for forcibly stopping the operation of converter 2 and inverter 3.

A method for stopping the operation of the converter and inverter will be specifically explained using FIG. 6. In FIG. 6, sequence controller 2
Contact _{S1 of a} relay _{( not shown} ) driven _{by the} output _of The outputs of the pulse amplification circuit 16 that controls the inverter 3 and the pulse amplification circuit 20 that controls the converter 2 are not applied to the converter 2 and the inverter 3 by short-circuiting between them.

By such a method, the operation of the converter 2 and the inverter is forcibly stopped, and then the contactor 2 is stopped by a signal from the sequence controller 22.
3, and the electromagnetic brake 5 is applied to stop and hold the elevator.

According to the embodiment of FIG. 5 of the present invention, overcurrent or overvoltage flowing through the converter or inverter is detected, the operation of the converter or inverter is forcibly stopped, the power supply is cut off, and an electromagnetic brake is applied. This makes it possible to prevent damage to the elements of the inverter device, burnout of the motor, and the like.

In addition, to protect the elevator control panel,
Generally, AC power supply 1 is supplied via a fuse free breaker (abbreviated as FFB), and if
If an overcurrent flows and the FFB trips, automatic rescue operation will not be possible, but if the overcurrent detection level is set to a value that will not cause the FFB to trip, the power can be turned off by turning on the contactor 23 again. Since the elevator will no longer be cut off, it will be possible to operate the elevator again, and automatic rescue operation will become possible.

Furthermore, if an overcurrent or overvoltage occurs, the elevator speed will abnormally increase or decelerate.
Since this is extremely dangerous, overcurrent and overvoltage are detected before such speeds are reached, and the electromagnetic brake is used to make an emergency stop, which improves safety.

In the embodiment shown in FIG. 6, a case has been described in which the main power source of the elevator is a three-phase AC power source, but it may be a DC power source using an engine generator or a battery. However, in the case of a battery, the converter 2 can be omitted.

Additionally, the method of forcibly stopping the converter and inverter is not limited to the above method.
Any method may be used as long as the same effect can be obtained. For example, there is a method of short-circuiting the bases and emitters of all transistors.

In the above embodiment, the regenerated power is returned to the AC power source using a regenerative converter, but this may also be done by connecting a resistor and a chopper device in parallel with the capacitor and causing the regenerated power to be consumed by the resistor. . In this case, the chopper device may be forcibly stopped.

Although the inverter has been described as an example of a voltage type inverter, it may also be a current type, and furthermore, although a transistor is used as the semiconductor control element, this may be a thyristor, a gate turn-off thyristor, or another device having the same function. It's okay.

FIG. 7 shows another embodiment of the present invention, in which the elevator speed may become abnormal for some reason, resulting in overcurrent or overvoltage, so the output of the elevator speed detection generator 12 is reduced. The output is input to the abnormal speed detection device 30 and its output is input to the sequence controller 22 to forcibly stop the operation of the converter 2 and inverter 3 even when the speed is abnormal, and then the contactor 23 is cut off and the electromagnetic brake 5 is
Activate to stop and hold the elevator.

According to the embodiment shown in FIG. 7, when the speed becomes abnormal and overcurrent or overvoltage occurs, the overcurrent or
Converters and inverters can be protected before overvoltage occurs.

〔Effect of the invention〕

According to the present invention, the voltage and current of the converter, inverter, AC power supply, electric motor, etc., or the speed of the elevator are monitored, and in the event of an abnormality, the operation of the inverter device is forcibly stopped, and then the power is cut off. However, since the electromagnetic brake is applied to stop and hold the elevator, it is possible to prevent the inverter device, electric motor, etc. from being damaged or burnt out in the event of the above abnormality, and it is also possible to safely stop the elevator and restart it. It can be done.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between the inverter's output frequency and output voltage, Figures 2 and 3 are output voltage waveform diagrams of the pulse modulation type inverter, and Figure 4 is when the inverter is controlled to have the characteristics shown in Figure 1. FIG. 5 is a block diagram of one embodiment of the present invention, FIG. 6 is a block diagram of the main circuit of FIG. 5, and FIG. 7 is a block diagram of another embodiment of the present invention. 1...Three-phase AC power supply, 2...Converter device, 3...
Inverter device, 4... Induction motor, 5... Electromagnetic brake, 9... Passenger car, 12... Speed generator for speed detection of elevator, 13... Speed command generator, 1
5, 19... PWM pulse generator, 22... sequence controller, 23... main circuit contactor, 24...
Filter device, 25... Overcurrent detection device for AC power supply, 26... Overcurrent detection device for converter 2, 27
...Overvoltage detection device, 28... Overcurrent detection device for inverter 3, 29... Overcurrent and overvoltage detection signal generation device, 30... Abnormal speed detection device for elevator,
_Tr1 to _Tr12 ...Transistor, _D1 to _D18 ...Diode, _S1 ...Inverter and converter stop contact.

Claims (1)

[Claims] 1. In an AC elevator equipped with an induction motor supplied with power by an inverter device and driven by the motor, an overcurrent that operates when a current or voltage of the inverter device is detected to be equal to or higher than a predetermined value; an overvoltage detection device, an abnormal speed detection device that detects an abnormal speed of the elevator, and an inverter forced stop that forcibly commands the inverter device to stop when at least the overcurrent or overvoltage detection device or the abnormal speed detection device operates. A control device for an AC elevator, comprising: a device; and a contactor that cuts off power to the inverter device after receiving the stop command. 2. The control device for an AC elevator according to claim 1, which is configured to cut off the power supply and operate the mechanical brake after stopping the inverter device.