JPH0825714B2 - Abnormal lifting stop device for suspended object lifts - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be driven by an electric motor, for example, as an apparatus for moving up and down various lances provided in a converter of a steel mill, a plasma torch for heating molten steel in a tundish, and the like. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension type object lifter for lifting and lowering, which relates to an abnormal lifting / lowering stop device for a suspended object equipped with an electromagnetic brake.

[0002]

2. Description of the Related Art In a hoist such as a device which is of a hanging type and is hoisted by an electric motor, when the hoist is stopped,
The brake is restrained (actuated) and the suspended object is held in its stop position.

As an example, a plasma torch lift for heating molten steel in a tundish of a steelmaking plant will be described.

In FIG. 2, 1 is a tundish, 2 is molten steel, 3 is a plasma torch which is an object suspended by a wire, and 4 is a torch elevator, which is a hoist for winding and unwinding the wire. It comprises a machine 5 and an electric motor 6 for driving the hoisting machine 5. 7 is an electromagnetic brake. Further, 8 is a torch position detector for detecting the insertion position of the plasma torch 3,
Reference numeral 9 is a molten steel 2 level detector. Then, the torch insertion height obtained from the torch position detector 8 and the molten metal surface detector 9
Based on the level of the molten steel 2 obtained from the above, the torch elevating / lowering command device 10 issues an operation command to elevate / lower the plasma torch 3.

The electric power supply circuit of the electric motor 6 for driving the hoisting machine 5 is
Via the motor main circuit switch 12 and power converter 11
Connected to a three-phase power supply. In this case, the power supply converter 11 generally uses a variable voltage / variable frequency power supply in order to improve the ascending / descending position accuracy of the plasma torch 3. Also, the circuit that operates the electromagnetic brake 7 is a brake.
It is connected to the three-phase power source through the switch 13 for use.
Reference numeral 14 denotes an electromagnetic switch control circuit that controls opening / closing of the motor main circuit switch 12 and the brake switch 13.

When a torch elevating command is issued from the torch elevating / lowering command device 10, this signal goes through the electromagnetic switch control circuit 14, and at the same time, the motor main circuit switch 12 and the brake open / close switch. The supply of the container 13 is established. As a result, the electromagnetic brake 7 is opened, a load current flows through the electric motor 6, and the plasma torch 3 moves up or down.

The distinction between rising and falling is made by a signal transmitted from the torch up / down command device 10 to the power converter 11 by a signal circuit provided separately.

[0008]

The main circuit current of the electric motor 6 flows so as to generate an electric motor torque which opposes the load of the plasma torch 3 which is a suspended object.

However, if there is a failure in the power converter 11 or the switch 12 for the electric motor main circuit, or a failure in the electric motor 6 (breaking of windings, etc.), no current flows in the electric motor 6, Therefore, no torque that can withstand the load of the plasma torch 3 is generated. At this time, if the electromagnetic brake 7 is excited, that is, opened by the operation command, the electric motor 6
And the hoisting machine 5 causes free rotation due to the tension of the wire,
A free fall of the plasma torch comes. When the suspended object falls, the suspended object itself is damaged and causes a serious accident.

In the present invention, disconnection occurs in the main circuit of the motor,
It is an object of the present invention to provide a device that stops abnormal lifting of a suspended object as described above when operating torque cannot be generated.

[0011]

In order to achieve the above-mentioned object, in the present invention, the feeding of an electric motor for driving a hoisting machine is performed.
Separately the electric circuit and the power supply circuit that operates the electromagnetic brake
Items that have an electric motor drive to wind or rewind
It is a lifting / lowering stop device for suspended objects in a body lift.
Electromagnetic brake operated by the brake opening / closing switch
In a lifting and lowering device equipped with, a non-current detector that detects a non-energized state in the power supply circuit of the electric motor that drives the hoisting machine, and whether there is a failure in the power supply circuit or the like depending on the non-current state detected by the non-current detector And a circuit for re-restraining the electromagnetic brake by shutting off the brake opening / closing switch when the abnormal up / down determination circuit determines that there is a failure.

[0012]

[Operation] Abnormal ascent / descent of a suspended object (for example, falling)
This occurs when the electromagnetic brake is open and the motor produces no running torque. The electric motor does not generate operating torque because no load current flows through the electric motor and its main circuit. In the present invention, whatever the cause of the load current not flowing, the presence / absence of energization is detected by the non-current detector, and when it is not energized, the electromagnetic brake is restrained and the suspended object is lifted or lowered abnormally. prevent.

[0013]

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, the same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, the currentless detector 15 is provided in the main circuit between the motor main circuit switch 12 and the motor 6.
Is connected. The currentless detector 15 is provided with one detector for each of the three phases. For this reason,
The non-current detector 15 can detect a state in which no current is applied even if there is a break in any phase of the main circuit of the electric motor 6 including the winding of the electric motor 6.

The abnormal lift determination circuit 16 comprises three contacts of the currentless detector 15, a failure determination relay 17, and a delay relay 18.

In the abnormal lift determination 16, if no current is detected in any phase of the currentless detector 15, the contact is closed and the failure determination relay 17 operates. The signal from the failure determination relay 17 is sent to the brake switch 13 via the electromagnetic switch control circuit 14 to open it, and the electromagnetic brake is opened.
The coil of key 7 is demagnetized and the brake 7 is restrained.

The delay relay 18 has a delay in the rise of the motor load current (about 0.1 to 0.5 sec) when the electric motor 6 is switched from the stopped state to the operation command. Is installed to prevent malfunction. Even when the current does not rise or the current after the rise is interrupted, the signal of the non-current detector 15 becomes valid after the time set in the delay relay 18 has elapsed.

In the following cases, the load current does not flow in the circuit of the electric motor 6 even if the electromagnetic brake 7 is opened by an operation command for moving the plasma torch 3 which is a suspended object up and down, and the plasma is not generated. According to the present embodiment, the torch 3 is in a state of causing a fall accident.
However, the plasma torch 3 can be prevented from falling.

When the variable voltage variable frequency converter, which is the power supply, fails and the expected output voltage cannot be obtained, when the power switch of the variable voltage variable frequency converter is cut off, the up / down operation command is transmitted due to transmission failure. When it cannot be transmitted to the switch for the main circuit of the motor, when the main circuit wiring including the winding of the motor is broken,

[0020]

According to the present invention, there is provided a non-current detector capable of detecting a non-energized state in the main circuit of the electric motor for driving the hoisting machine, and the non-current detector detects the non-current state of the electric motor. Has a circuit that opens the break switch to restrain the electromagnetic brake.

Therefore, according to the present invention, when the electric motor is operated in a non-current state, the electromagnetic brake works to avoid an abnormal ascending / descending accident such as a hanging object falling.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is an example of a conventional fall prevention device for a hanging-type object elevator, and is an explanatory view of a fall prevention device for a plasma torch elevator when heating molten steel in a tundish.

[Explanation of symbols]

 1 Tundish 2 Molten steel 3 Plasma torch which is a suspended object 4 Torch lift 5 Hoisting machine 6 Electric motor that drives hoisting machine 7 Electromagnetic brake 8 Torch position detector 9 Molten steel level detector 10 Torch lift commander 11 Power converter 12 Motor main circuit switch 13 Breaker switch 14 Electromagnetic switch control circuit 15 No-current detector 16 Abnormal lift determination 17 Failure determination relay 18 Delay relay

Claims (1)

[Claims] 1. A power supply circuit for a motor for driving a hoist and an electromagnetic
It has a power supply circuit that activates the brake, and is a lifting / lowering stop device for suspended objects in an elevator that hoists and rewinds by driving a motor , and an up / down stop equipped with an electromagnetic brake that is operated by a brake switch. In the equipment, a non-current detector that detects the non-energized state in the power supply circuit of the electric motor that drives the hoisting machine, and an abnormality that determines whether there is a failure in the power supply circuit or the like based on the non-current state detected by this non-current detector And a circuit for re-restraining the electromagnetic brake by shutting off the brake switch when the abnormal up-down determination circuit determines that there is a failure. Lifting device for abnormal lift of a moving object lifter.