JPH0130756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an elevator control device that energizes an induction motor with variable voltage and variable frequency alternating current to raise and lower a car, and particularly relates to protection of the control device.

Note that when an induction motor is energized with alternating current of variable voltage and frequency, any rotational speed can be obtained.
Recently, it has been considered to apply variable voltage variable frequency control (hereinafter referred to as VVVF control) to elevators.

By the way, VVVF control converts alternating current from a commercial power source into direct current, and further converts it into alternating current with variable voltage and variable frequency. Because the motive power source is converted in this manner, protection measures have been used throughout to protect against overcurrents due to failure of each converter.

FIG. 1 shows a conventionally proposed elevator control device.

In the figure, R, S, and T are three-phase AC power supplies; 1 is a converter that is connected to the three-phase AC power supplies R, S, and T to convert AC into DC at a constant voltage; 2 is a capacitor that smoothes this DC; 2a is a DC current transformer that measures the current flowing through this capacitor 2, and 3 is activated when the signal of this DC current transformer 2a exceeds a specified value to open a normally closed contact 3a and to disconnect the inverter described later. The protection means 4 is a resistor that consumes regenerated power, has a relatively low resistance value, and burns out if it is constantly energized. Reference numeral 4a denotes a current limiting means consisting of a transistor that becomes conductive and causes a current to flow through the resistor 4 when electric power is being regenerated, and functions together with the resistor 4 as a recirculating power processing device. 5 is a protection means consisting of an overcurrent relay that opens a normally closed contact 5a when the current flowing through the resistor 4 exceeds a predetermined value; 6 is usually composed of a transistor, and converts the direct current from the converter 1 into a variable voltage variable frequency converter. Inverter that converts to three-phase alternating current,
7 and 8 are protective means consisting of overcurrent relays connected to two phases of the three-phase alternating current converted by this inverter 6, and when a current exceeding a predetermined value flows, normally closed contacts 7a and 8a are opened, respectively. It is something to do. 9 is an induction motor powered by alternating current from the inverter 6, 10 is a drive shaft directly connected to this induction motor 9, 11 is a brake wheel connected to this drive shaft, and 12 is a spring (not shown) attached to this brake wheel 11. 13 is a brake coil that releases the brake shoe from the brake wheel 11 against the spring force when energized, and 14 is a drive. A speedometer connected to the shaft 10 detects the number of revolutions of the induction motor 9, and 15 is a mesh wheel connected to the drive shaft 10, which drives the car 17 and the counterweight 18 up and down via the main rope 16. be. 19 is a speed pattern generating means for generating a speed pattern signal of the induction motor 9; 20 is a comparator for comparing this speed pattern signal with the speed signal of the speedometer 14; and 21 is an inverter based on the comparison result of this comparator 20. 6, an inverter driving means for driving 22, a normally closed contact 3;
The circuit breaker is connected between AC power supplies S and T through a series circuit of a, 5a, 7a, and 8a, and is always energized to close contact 22a and connect converter 1 to AC power supplies R, S, and T. When connected and deenergized, contact 22a
It opens and separates the

Next, to explain the outline of the operation, in normal times, the circuit breaker 22 is energized, so the contact 22a is closed, and the alternating current from the alternating current power supplies R, S, and T is converted to direct current by the converter 1. has been done. This direct current is smoothed by a capacitor 2. At this time, a current flows through the capacitor 2, but the value is very small, and the normally closed contact 3a is not opened. When the speed pattern generator 19 generates a speed pattern signal, the brake shoe 12 is released and the inverter 6 outputs an alternating current corresponding to the speed pattern signal. The induction motor 9 is energized by this alternating current, and the car 17 is driven up and down.

When the induction motor 9 acts as a generator and generates electric power, the inverter 6 reversely converts the alternating current into direct current. At this time, the transistor 4a becomes conductive and the regenerative power is consumed by the resistor 4, so the induction motor 9
generates braking torque and rotates at the intended speed.

Next, protection against overcurrent will be described.

First, when an overcurrent flows through the induction motor 9, the overcurrent relays 7 and 8 operate, opening the normally closed contacts 7a and 8a, and deenergizing the circuit breaker 22. This deenergization opens the contacts 22a and disconnects the converter 1 from the AC power supplies R, S, T, so that the induction motor 9 can be protected. Furthermore, if a short-circuit failure occurs in the inverter 6 for some reason, power is supplied not only from the converter 1 but also from the capacitor 2, causing a steep large current to flow. At this time, the DC current transformer 2a measures the large current flowing out from the capacitor 2 and inputs it to the current detection means 3. This current detecting means 3 outputs a cutoff signal to invert the inverter 6.
The base of the transistor that makes up the circuit is forcibly biased negatively to prevent short-circuit current. Also, even if it cannot be prevented, contact 22
Cut off the subsequent current by releasing a,
The converter 1, electric wires, etc. are protected against large currents.

Furthermore, if transistor 4a fails and becomes constantly conductive, not only regenerated power but also direct current from converter 1 flows, so resistor 4 becomes constantly energized and there is a risk of overheating.
At this time, the overcurrent relay 5 is heated by this current and opens the normally closed contact 5a. As a result of this opening, the contact 22a is opened as already mentioned,
Since the power supply is cut off, it is possible to prevent the resistor 4 from burning out.

By the way, in the elevator control device shown in FIG. 1, a current detection means 3 and overcurrent relays 5 and 7 are used as protection devices in each circuit,
It is designed to protect against overcurrent. When a large number of protection means are used in this way, for example, when a large current flows through the induction motor 9, the overcurrent relay 7 and the current detection means 3 may be activated simultaneously, resulting in a disadvantage that it takes time to recover after the fact. It was hot. Another disadvantage was that it was expensive due to the large number of protective measures.

This invention was made in view of the above-mentioned drawbacks, and FIG. 2 shows one embodiment of this invention.

In the figure, the same reference numerals as in Figure 1 indicate the same parts, and 30
An electric wire a has one end connected to the positive electrode of a circuit in which a capacitor 2 is connected between the positive and negative electrodes on the DC side of the converter 1, and the other end is connected to a resistor 4 and an inverter 6. Similarly, 30b is an electric wire having one end connected to the negative electrode, and the other end connected to the transistor 4a and the inverter 6. 31 is the electric wire 30a
A DC current transformer 32 that measures the current of the DC current transformer 31 is a protection means consisting of a current detection means that is activated to open the normally closed contact 32a when the signal from the DC current transformer 31 exceeds a predetermined value.

Next, regarding the operation, in normal times, the first
Since this is the same as the conventional example shown in the figure, the explanation will be omitted, and protection against overcurrent will be described.

First, when an overcurrent flows through the induction motor 9, its active power becomes a DC side current and the electric wires 31a, 3
1b and is measured by the DC current transformer 31. Since this measurement signal is larger than in normal times, the current detection means 32 is activated and the normally closed contact 32a is opened. This opening deenergizes the circuit breaker 22, opens the contact 22a, and cuts off the overcurrent.

Furthermore, if the transistor 4a fails and continues to conduct, current will always flow through the resistor 4. This current is measured by the DC current transformer 31, and the current detection means 3
2 is activated, and the circuit breaker 22 is deenergized. This deenergization cuts off the power and prevents the resistor 4 from burning out.

Furthermore, if a short circuit occurs in the inverter 6, a large current flows through the electric wires 30a and 30b due to the short circuit, and the DC current transformer 31 generates a large measurement signal. When the current detection means 32 is activated by this measurement signal, it outputs a cutoff signal to make the inverter 6 non-conductive, thereby blocking the short-circuit current and opening the normally open contact 32a in case it cannot be blocked. This opening deenergizes the circuit breaker 22, opens the contact 22a, cuts off the power, and protects the converter 1 and the electric wires 30a, 30b from a large current caused by a short circuit accident in the inverter 6.

Although the contact 22a is connected between the AC power supplies R, S, and T and the converter 1, it is not limited to this, and the intended purpose can be achieved even if the contact 22a is connected to the electric wires 30a and 30b. Can be done.

As described above, this invention connects a converter that is connected to an AC power source and converts the AC into DC, and a circuit that has a capacitor connected between the positive and negative electrodes on the DC side of the converter, through an electric path.
In an elevator control device that connects a resistor that is energized when necessary and an inverter that converts the above-mentioned direct current to alternating current, and energizes an induction motor with the converted alternating current, the current detection means is located closer to the inverter than the capacitor. The regenerative power processing device is connected to the opposite side of the inverter, and when this current detection means detects a current exceeding a predetermined value, the power supplied from the AC power source is cut off. Even if a large current flows through the induction motor, or a large current flows through the induction motor, both can be detected by the current detection means, and by this detection, burnout can be prevented by cutting off the AC power supply.

In other words, overcurrent countermeasures can be taken all at once instead of separately, which simplifies the circuit configuration.In addition, even when improving the reliability of the protection circuit, it is only necessary to take measures for the current detection means. This has the advantage of being easier than if it were done for each motor or induction motor.

Furthermore, since the current is detected on the inverter side rather than the capacitor, if a continuity failure occurs in the regenerative power processing device, it can be detected under certain conditions, such as immediately after the elevator stops, so that current should not flow to the regenerative power processing device. Additionally, current flows due to this continuity failure, and this can be detected, resulting in a high level of safety.

Furthermore, when the AC power source is turned on at the start of operation, a charging current flows into the capacitor, but even if this inflow current is excessive, it also has the effect that the current detection means will not malfunction due to this current.

[Brief explanation of drawings]

FIG. 1 is a control circuit diagram showing a conventional elevator control device as a block diagram, and FIG. 2 is a control circuit diagram showing an embodiment of the present invention. In the figure, R, S, and T are AC power supplies, 1 is a converter, 2 is a capacitor, 4 is a resistor, 4a is a current limiting means, 6 is an inverter, 9 is an induction motor, 22 is a circuit breaker, and 30a and 30b are electric circuits. , 32
is a current detection means. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A converter connected to an AC power supply converts alternating current to direct current, and an inverter converts this direct current to alternating current of a desired frequency to drive an induction motor and drive a car, which is connected to the above-mentioned direct current circuit. a smoothing capacitor connected between the smoothing capacitor and the inverter, a regenerative power processing device that operates during regenerative operation of the induction motor and consumes the regenerated power; An elevator comprising a current detecting means connected to the side opposite to the inverter from the regenerative power processing device, and a means for cutting off the current flowing from the AC power source to the converter when the current detecting means detects a current of a predetermined value or more. Control device.