JPH04210790A - Hoist for ladle crane - Google Patents

Abstract

PURPOSE:To realize safety lowering operation at a rated load by additionally providing the electric circuit for a drive unit with a reverse phase brake operation circuit which disconnects a faulty motor, connects the remaining motors with secondary resistors for two motors and applies reverse phase brake. CONSTITUTION:Electromagnetic contactors E1, E2, E3 for switching resistor are additionally provided on the secondary of a motor. Upon failure of one motor, an emergency lowering operation switch is turned ON. Consequently, the secondary resistor of faulty motor is disconnected therefrom through function of the electromagnetic contactor and connected with a normal motor. Upon failure of motor M1, for example, the electromagnetic contactor E1 is opened, E2 is closed and E3 is closed thus connecting a secondary resistor R2 in parallel with a motor M2. Since two resistors are connected in parallel with the motor, secondary current of motor is shunted to two resistors thus doubling the thermal capacity of the resistor which thereby is not overheated even under 100% load.

Description

[Detailed description of the invention]

[00011

[Industrial Field of Application] The present invention relates to a hoisting device for a ladle crane used when moving hot metal or molten steel at a steelworks or the like. [0002] [0002] In order to improve safety, the hoisting device of a ladle crane is usually designed to hoist a hook 5 of a ladder 6 using two sets of drums 4.4, as shown in FIG. . The drum 4.4 is connected to two sets of electric motors 1.1 via the reducer 3.
and brake 2.2. The mechanism is designed so that even if one electric motor 1 breaks down, the remaining one electric motor 1 can drive two sets of drums 4.4 via the reducer 3 to raise and lower the hook 5. . [00031 FIG. 5 shows a circuit diagram of a normal hoisting device. Similarly, for the electric circuit, two sets of control devices are provided for controlling the two sets of electric motors M1 and M2. That is, in FIG. 5, two sets of molded circuit breakers MCBI and MCB are used for motor-next control.
2. Reversible electromagnetic contactors F1, R1, F2, R2 Deceleration control electromagnetic contactors DBI and DB2 are provided. Two sets of secondary resistors R1 and R2 for motor secondary control, and acceleration magnetic contactors 11A, 12A, 13A, 14A, 21A, 22
Two normal electric motors consisting of A, 23A, and 24A are operated simultaneously. [0004] If one electric motor fails, a molded circuit breaker M is installed so that the various electromagnetic contactors on the failed side will not operate.
The CBI or MCB2 was disconnected and the remaining electric motor was operating. The speed-torque characteristics at this time are shown in FIG. That is, the suspended load escapes because the electric motor electric braking force B is A>B with respect to the 100% load hoisting torque A. Therefore, in conventional cranes, emergency lowering was performed by inching the stopping brake. [0005]

[Problem to be solved by the invention] However, even if two systems of conventional hoisting equipment are installed, one system only takes up 50% of the lifting load.
Designed with. Therefore, as shown in the speed-torque characteristic of FIG. 5, with one electric motor, stable operation could not be achieved because the motor torque B during low-speed lowering operation was smaller than the rated (100%) load lowering torque A. Furthermore, the secondary resistors R1 and R2 shown in FIG. 5, and the electromagnetic contactor 11 for shorting the secondary resistor
A~14A and 21A~24A are each 50% of the lifting load.
Because of the design, the capacity was insufficient to withstand emergency operation with a single electric motor. Therefore, with the conventional ladle crane hoisting device, it was not possible to safely lower the 100% load lifted by operating one electric motor. [0006] The present invention was developed to address the above-mentioned problems, and in the event that one drive machine fails, the rated (100%) load can be safely lowered with the remaining electric motor. The purpose is to enable driving. [0007]

[Means for solving the problem] One electric motor is rated (10
0%) In order to safely lower the load in an emergency, a reverse phase braking operation circuit is added to the electric motor to perform the lowering operation while generating torque in the hoisting direction during the emergency lowering operation. Furthermore, during emergency lowering operation, the secondary resistors for two motors are connected in parallel to prevent the secondary resistors from overheating during rated (100%) load emergency lowering operation. do. [0008] By combining the above two items, emergency lowering operation of rated (100%) load is possible with one electric motor. [0009]

[Operation] According to the above-mentioned means, when one electric motor fails, the remaining one electric motor can be used for 100 seconds without using the stopping brake by using the electric braking force of the electric motor.
% load can be lowered safely. [00101

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a circuit diagram of a hoisting device with an emergency hoisting circuit. The major difference from the conventional circuit is that electromagnetic contactors E1, F2, and F3 for switching resistors are added to the secondary side of the motor. The operation of the electromagnetic contactor shown in FIG. 2 is illustrative of the operation of the various electromagnetic contactors shown in the circuit of FIG. During normal operation, it moves in the same way as a conventional crane. In the event that one of the motors breaks down, the electromagnetic contactor operates as shown in Figure 2 by switching the selector switch and operating the emergency lowering operation switch. [00111 That is, by the action of the resistor switching electromagnetic contactor, the secondary resistor of the faulty motor is disconnected from the faulty motor and connected to the remaining normal motor. For example, in Fig. 1, when motor M1 fails, magnetic contactor F1 is disconnected, F2 is connected, and F
The secondary resistor R1 is connected in parallel to the electric motor M2. Since two sets of resistors are connected in parallel to one motor, the motor secondary current is shunted to the two resistors, so the heat capacity of the resistor is doubled, and the heat capacity is usually the same as when two motors are operated. The resistor no longer overheats even under 100% load. Co 012] In the above state, when the emergency hoisting operation switch is operated, the hoisting electromagnetic contactor, Fl or F2, is brought into contact and 100% of the load can be hoisted down by plaking braking (reverse phase braking). The speed-torque characteristics at this time are shown in FIG. That is, the 100% load emergency lowering load torque A and the electric motor brake torque B are balanced at point C, and lowering operation can be performed at a stable speed. When the emergency lowering operation switch is turned off, the locking brake is activated and the suspended load is held. [0013] As described above, according to the present invention, the failed motor is disconnected from the electric circuit of the drive device, and the remaining motor is connected to the motor 2.
A reverse braking circuit is added that applies reverse braking by contacting the secondary resistors of each machine, so in the case of a conventional ladle crane, if one electric motor fails, 100% load unloading is done using the stopping brake, which is extremely dangerous. However, thanks to the present invention, it is now possible to lower the vehicle safely. In addition, in the present invention, the additional equipment required for 100% emergency lowering can be obtained with only three electromagnetic contactors and a relay circuit to obtain the same performance, so the additional equipment cost can be reduced compared to increasing the weight and size of the motor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a hoisting device of the present invention.

FIG. 2 is a table of three electromagnetic contactors of the present invention.

FIG. 3 is a speed-torque characteristic diagram of the present invention.

FIG. 4 is a configuration diagram of a hoisting device.

FIG. 5 is a circuit diagram of a conventional hoisting device.

FIG. 6 is a conventional speed-torque characteristic diagram.

[Explanation of symbols]

M Electric motor R secondary resistor

[Figure 4]

Claims (1)

[Claims] Claim 1: In a hoisting device for a ladle crane consisting of two sets of drive devices, a faulty motor is disconnected from the electric circuit of the drive device, and a secondary resistor for two motors is connected to the remaining motor. , a ladle crane hoisting device characterized by adding a reverse phase braking operation circuit that applies reverse phase braking.