JPH034476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter hoist, and more particularly to a variable speed inverter hoist whose hoisting speed can be varied by an inverter device.

[Conventional technology]

As shown in Fig. 1, a conventional inverter hoist has a high resistance 11 connected in parallel with a smoothing capacitor 3.
It is known that the resistor 11 is used to discharge the charge stored in the capacitor 3 when the high source is cut off.

[Problem to be solved by the invention]

However, the resistor 11 has a fairly high resistance in order to reduce power consumption during operation and improve efficiency.
For this reason, the discharge time of the capacitor 3 after the power is cut off becomes long, and if maintenance or the like of the hoist main body is performed immediately after the power is cut off, it is a risky inspection. In particular, in the case of a hoist, the regenerative voltage during lowering is high, and the terminal voltage of the smoothing capacitor 3 is rising, resulting in an extremely dangerous situation.

In this type of hoist driven by an inverter, a smoothing capacitor is generally used to convert the power source of the inverter to direct current, which causes the above-mentioned problem. As a method to solve these problems, regarding an electronic circuit with a capacitor, a method is described in Figure 3 of Utility Model Application Publication No. 164846/1983, in which a capacitor discharge circuit is formed in conjunction with a power switch when the power is cut off. There is. However, although the electronic circuit described in this publication is presumed to be effective in disconnecting the discharge circuit during operation and improving efficiency, it does not take into account protection in the event of a failure or malfunction of the interlock switch. Not yet.

In addition, the life of a capacitor will be shortened if it undergoes repeated rapid discharges, but in the case of the capacitor described in this publication, the discharging switch is frequently connected and disconnected when the power switch is opened and closed.
Each time the capacitor is charged and discharged, its lifespan will be shortened. It also has the problem of. When the capacitor disappears, it no longer functions as a device, and the lifespan of the device is also limited.

The purpose of the present invention is to be able to safely perform maintenance after the power is shut off without increasing power consumption during operation, and to prevent the regenerative resistor from burning out due to the formation of a capacitor discharge circuit by mistake during operation. To provide a double safety inverter hoist that prevents premature deterioration of the capacitor.

[Means for solving problems]

In particular, in an inverter-driven hoist, a series circuit consisting of a regenerative resistor 10, a B contact 16 that is closed when the electromagnetic relay coil 14 is de-energized, and a manual switch 17 is connected to both ends of the smoothing capacitor 3, and the electromagnetic This is achieved by configuring the B contact to close when the contactor MC is opened, and by artificially closing the manual switch 17, to form a discharge circuit for the smoothing capacitor 3 through the regenerative resistor 10. Ru.

[Effect]

In the present invention, the discharging circuit is disconnected during operation, thereby reducing wasted power during operation, and the manual switch acts to form a discharging circuit during maintenance, and the manual switch connected in series with the B contact is It protects the regenerative resistor even if the closing is not restored due to an accident or the like, and acts to forcibly form a discharge circuit.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIG. 2.

The inverter device 1 is shown by a dashed line and is composed of a converter 2, a smoothing capacitor 3, an inverter unit 4, an inverter control circuit 5, and the like. 6 is a hoisting motor connected to the inverter unit, 14 is an electromagnetic contact placed on the power line
This is an electromagnetic relay coil that opens and closes the MC. A regeneration device 7 is connected between the positive and negative terminals of the smoothing capacitor 3. Also, electromagnetic contactor
A brake solenoid 15 that opens when energized is connected to the output side of the MC.

The regeneration device 7 includes a discharge switching transistor 8, a base drive circuit 9 that turns on the transistor 8 when the voltage across the smoothing capacitor 3 exceeds a certain value (for example, 350V), and a regeneration resistor 10 on the output side of the transistor 8. is connected.

Further, a series circuit of a B contact 16 of an electromagnetic relay coil 14 and a manual switch 17 is connected in parallel with the switching transistor 8.

The inverter hoist is operated and stopped by a power switch 18. When the power switch 18 is turned on, the electromagnetic relay coil 14 is energized, the brake is released, and the inverter device 1 rotates the hoisting motor 6 at a set speed based on the hoisting/lowering input signal and the speed command input signal. Note that 12 is a hoisting/lowering command device, and 13 is a speed command device. At this time, the B contact 16 of the electromagnetic relay coil 14 is open, and the operation of the manual switch 17 has no effect. During lowering operation, regenerated power flows backward through the inverter unit 4,
The terminal voltage of smoothing capacitor 3 is increased, and the voltage is
When the voltage exceeds 350V, the switching transistor 8 becomes conductive and the regenerative power is consumed by the regenerative resistor 10.

When the power switch 18 is shut off, the electromagnetic relay coil 14 becomes open circuit, and the brake solenoid 15
operates and the hoisting motor 6 stops, but a high DC voltage remains in the smoothing capacitor 3. In this state, if the manual switch 17 is manually closed when performing maintenance etc., the B contact 16 of the electromagnetic relay coil 14 is closed, so the capacitor 3 including the regenerative resistor 10 (for example, 40Ω) is closed. A discharge circuit is formed and the charge is discharged very quickly. Therefore, according to one embodiment of the present invention, the B contact 16 of the electromagnetic relay coil 14 for switching on and off the power supply is connected to the discharge circuit by the manual switch 17.
are connected in series, so even if the manual switch 17 is accidentally turned on during hoist operation, a discharge circuit is not formed and there is no risk of the regenerative resistor 10 being burnt out.

In other words, even if the B contact, which is frequently connected and disconnected, does not return to its closed state due to some reason, a discharge circuit will not be formed unless the manual switch is manually forced to close, so there is no possibility of erroneous operation during operation. Therefore, a large current will flow through the regenerative resistor and accidents such as burnout will not occur.

Furthermore, since the discharge circuit is configured to be formed only when maintenance or the like is necessary, the life of the capacitor can be extended as much as possible, and the life of the circuit and, by extension, the device can be extended as much as possible.

〔Effect of the invention〕

As described above, the present invention provides an inverter hoist in which, in particular, both ends of the smoothing capacitor 3 are
A series circuit of a regenerative resistor 10, a B contact 16 which is closed when the electromagnetic relay coil 14 is de-energized, and a manual switch 17 is connected, and when the electromagnetic contactor MC is opened, this B contact is closed and the manual switch 1 is closed.
Since the discharge circuit of the smoothing capacitor 3 passing through the regenerative resistor 10 is formed by artificially closing 7, the power consumption during operation is reduced, and maintenance after the power is cut off can be performed safely. Furthermore, since a capacitor discharge circuit is not accidentally formed during operation, there is no risk of the regenerative resistor being burnt out, and the life of the capacitor is extended, making it possible to provide a double-safety inverter hoist. It is something.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a conventional electric hoist, and FIG. 2 is a circuit block diagram of an electric hoist according to the present invention. 1...Inverter device, 2...Converter, 3
... Smoothing capacitor, 4 ... Inverter unit, 5 ... Inverter control circuit, 10 ... Regeneration resistor, 16 ... B contact, 17 ... Manual switch.

Claims (1)

[Claims] 1. A power source and an inverter unit 4 connected to this power source and having a smoothing capacitor 3 on its input side.
An inverter control circuit 5 that controls this inverter unit, a hoisting motor 6 connected to this inverter unit 4, an electromagnetic relay coil 14 connected to the power source, and the power source is controlled by the action of this electromagnetic relay coil. A magnetic contact (MC) that opens and closes, a power switch 18 connected in series to the electromagnetic relay coil 14, a brake solenoid 15 connected between the magnetic contact (MC) and the inverter unit 4, and a magnetic contact ( MC) and a smoothing capacitor 3 disposed between the inverter unit 4, a regenerative resistor 1 is connected to both ends of the smoothing capacitor 3.
0, a series circuit of the B contact 16 and the manual switch 17 which are closed when the electromagnetic relay coil 14 is de-energized is connected, and when the electromagnetic contactor (MC) is opened, this B contact is closed and the manual switch 17 is artificially closed. An inverter hoist characterized in that the inverter hoist is configured to form a discharge circuit for the smoothing capacitor 3 passing through the regenerative resistor 10 when closed.