JPH0311195B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a device for controlling an elevator driven by an induction motor.

[Prior art]

Some elevators use an induction motor as the motor that drives the car, and supply variable voltage/variable frequency alternating current power converted by an inverter to control the speed of the motor. In this device, when the car is lowering a heavy load, increasing a light load, or decelerating, mechanical energy is converted into electrical energy and returned to the DC side via an inverter.
When a DC power supply is composed of a rectifier and a smoothing capacitor, the terminal voltage of the smoothing capacitor increases, and there is a possibility that dielectric breakdown of the elements constituting the inverter will occur. Furthermore, if the ratio between the voltage applied to the motor and the frequency exceeds a predetermined value, the magnetic flux of the motor may become saturated and an excessive current may flow. Therefore,
In order to process the electric power regenerated on the DC side, a regeneration converter is used, for example, as shown in Japanese Patent Application Laid-Open No. 162477/1983. This will be further explained with reference to FIG.

In the figure, R, S, and T are commercial three-phase AC power supplies, 1 is a molded circuit breaker that cuts off AC power supplies R, S, and T, and 2 is connected to circuit breaker 1, and diodes 2A to 2F are used to shut down all three phases. The power supply converter 3 in which a wave rectification circuit is formed is a smoothing capacitor connected to the DC side of the power supply converter 2, an inverter 4 connected to both ends of the smoothing capacitor 3, and six transistors 4.
A to 4F and six diodes 4a to 4f, transistors 4A to 4F are connected in parallel in three sets, two of which are connected in series, and transistors 4A to 4F each include a diode 4a to 4F.
~4f are connected in parallel, and are well-known inverters of the pulse width modulation method that convert constant DC voltage to variable voltage/variable frequency AC; 5 is a three-phase induction motor connected to the AC side of inverter 4; 6 is a driving sheave of a hoist driven by an electric motor 5, 7
8 is a main rope wrapped around the sheave 6, 8 is a cage connected to one end of the main rope 7, 9 is a counterweight also connected to the other end, and 10 is a three-way cable whose primary side is connected to the circuit breaker 1. A phase transformer 11 is a regenerative converter connected to the secondary side of the transformer 10 and forming a three-phase full-wave rectifier circuit with thyristors 11A to 11F.
One end of the DC side is connected to one end of the smoothing capacitor 3 via the DC reactor 12, and the other end of the DC side is connected to the other end of the smoothing capacitor 3.

In other words, when driving in a row, the AC power supplies R, S, T
The alternating current power is converted to direct current by the converter 2 for direct current, smoothed by the smoothing capacitor 3, and then pulse width controlled by the inverter 4, and the alternating current is supplied to the motor 5 with variable voltage and variable frequency. Supply electricity. Now, the electric motor 5 starts and the car 8
runs and its speed is controlled. On the other hand, during regenerative operation, the electric power generated by the electric motor 5 is transferred to the inverter 4.
is converted into direct current through the regenerative converter 11.
It is returned to AC power supplies R, S, and T via. At this time, the transformer 10 is a transformer that makes the AC side voltage of the regenerative converter 11 slightly higher than the voltages of the AC power supplies R, S, and T in order to ensure the commutation of the regenerative converter 11. In this case, an autotransformer or an isolation transformer is used.

Now, during regenerative operation, for some reason, circuit breaker 1
operates or when the AC power supplies R, S, and T are out of power, the electric motor 5 is braked by a brake (not shown), but the electric charge stored in the smoothing capacitor 3 is transferred to the DC reactor 12 and the regeneration converter. 11 into the transformer 10, where a large short circuit current flows. Although the DC reactor 12 is intended to suppress this current and prevent damage to the regenerative converter 11, it is inevitably large and expensive. Another way to prevent this short-circuit current is to insert a high-speed circuit breaker into the circuit, but a circuit breaker that cuts off a large DC current within a short time is
This is also large and expensive.

[Summary of the invention]

This invention aims to improve the above-mentioned problems, and by using a self-extinguishing element in the regenerative converter, it is possible to construct an inexpensive device that prevents the regenerative converter from being destroyed by the large current that flows when AC power is lost. The object of the present invention is to provide a control device for an AC elevator.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows an overall configuration diagram of the present invention.

In the figure, 1A is a circuit breaker operation detection contact that operates in conjunction with the operation of circuit breaker 1 and closes when circuit breaker 1 interrupts the circuit, and 14 is a power failure detection relay that detects a power failure of AC power supplies R, S, and T. , 15A, 15B are current transformers that detect the current on the alternating current side of the regenerative converter 11, and when the contact 1A is closed or the power failure detection relay 14
is deenergized, current transformer 15A or current transformer 15B
When the output becomes abnormal, an arc extinguishing signal is given from the control circuit 16 to the regeneration converter 11. At this time, since the regenerative converter 11 is constituted by a self-extinguishing element as described later, the regenerative converter 11 is cut off and the regenerative current is not returned to the AC side.

FIG. 3 shows a circuit diagram of the embodiment.

In the figure, 11 indicates six transistors 11G to 11.
Consisting of L and 6 diodes 11g to 11l,
Three sets of transistors 11G to 11L are connected in parallel, two of which are connected in series, and diodes 11g to 11l are connected in parallel to each of the transistors 11G to 11L.The DC side thereof is a smoothing converter. It is connected to both ends of the capacitor 3 (the DC reactor 12 in FIG. 1 is not used). 17 is a control device composed of a microcomputer, and is called a central processing unit (hereinafter referred to as a central processing unit).
(hereinafter referred to as CPU) 17A, read-only memory (hereinafter referred to as
(referred to as ROM) 17B, a read/write memory 17C that temporarily stores data such as calculation results, a conversion device 17D that is connected to the circuit breaker operation detection contact 1A and converts the input/output signal level, and also inputs the signal of the power failure detection relay 14. Conversion device 17E, conversion device 1 that also inputs signals from current transformers 15A and 15B.
7F, 17G, and a conversion device 17H that outputs a base cutoff signal, that is, an arc extinguishing signal for transistors 11G to 11L of the regenerative converter 11.
Other than the above, the configuration is the same as in FIG. 1.

Next, the operation of this embodiment will be explained using the flowchart of the operation shown in FIG.

In step 21, the operation of circuit breaker 1 is detected, and in step 22
If it is determined that the circuit breaker 1 is not operating (contact 1A is open), normal operation is performed in step 23.
Circuit breaker 1 operated in step 22 (contact 1A closed)
If it is determined that this is the case, an arc extinguishing signal is issued in step 24. As a result, transistors 11G to 11L of regenerative converter 11 become non-conductive, and no current flows through regenerative converter 11. Also, step 2
Detect the voltages of AC power supplies R, S, and T in step 5, and proceed to step 2.
If it is determined in step 6 that AC power supplies R, S, and T are not in a power outage (power outage detection relay 14 is energized), normal operation is performed in step 23, and there is a power outage (power outage detection relay 1 is energized).
4), an extinguishing signal is issued in step 24. Further, in step 27, the current on the alternating current side of the regenerative converter 11 is detected, and if the current is below a predetermined value in step 28, normal operation is performed in step 23, and if the current exceeds the predetermined value, the step 24
The arc extinguishing signal is issued.

In this way, the contact 1A is closed, the power failure detection relay 14 is deenergized, or the current transformer 15
When either A or 15B detects a large current, an arc extinguishing signal is issued, the regenerative converter 11 is cut off, and the discharge circuit of the smoothing capacitor 3 is no longer formed. Therefore, no large current flows through the regenerative converter 11 and the transformer 10, so
They are prevented from destruction.

Note that in the above embodiment, the transistors 11G to
Although 11L is used in this embodiment, the same function can be achieved by using a gate turn-off transistor.

〔Effect of the invention〕

As described above, in this invention, AC power is supplied from an inverter to an induction motor for driving an elevator, a regenerative converter is connected in parallel to a power converter that supplies DC power to the inverter, and the regenerative converter is connected in parallel to the inverter. Consisting of self-extinguishing elements, when loss of commercial AC power is detected,
The self-arc-extinguishing element is made non-conductive by emitting an arc-extinguishing signal.

As a result, it is possible to construct an inexpensive device that blocks a large current flowing due to regenerative power and prevents damage to the regenerative converter when commercial AC power is lost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional AC elevator control device, FIG. 2 is an overall configuration diagram showing an embodiment of an AC elevator control device according to the present invention, and FIG.
This figure is also a circuit diagram of the main part, and FIG. 4 is a flowchart of the operation by the control circuit of FIG. 3. In the figure, R, S, and T are commercial three-phase AC power supplies, 1 is a molded circuit breaker, 1A is a circuit breaker operation detection contact, 2 is a power supply converter, 3 is a smoothing capacitor, 4 is an inverter, and 5 is a three-phase Induction motor, 8 is cage, 11 is regeneration converter, 14 is power failure detection relay, 15
A and 15B are current transformers, and 17 is a control device. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A smoothing capacitor is connected to the DC side of a power converter that is connected to a commercial AC power source and converts AC to DC, and an inverter is connected to both ends of this smoothing capacitor. A device that operates a car by supplying variable voltage/variable frequency alternating current to an induction motor, which is constructed of a self-arc-extinguishing element that is connected in parallel with the above-mentioned car-carrying converter and becomes non-conductive when an arc-extinguishing signal is applied. a regenerative converter that returns regenerated power from the electric motor to the commercial AC power source; a power failure detection circuit that detects loss of the commercial AC power; and when the power failure detection circuit operates, the self-extinguishing element causes the self-extinguishing element to A control device for an AC elevator, comprising: a control circuit that supplies an arc signal. 2. A control device for an AC elevator according to claim 1, which uses a transistor as a self-extinguishing element. 3. A control device for an AC elevator according to claim 1, which uses a gate turn-off thyristor as the self-extinguishing element.