JPS5918880Y2 - Emergency operation circuit for multiple AC winding type motor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an emergency operation circuit when a plurality of AC wound induction motors are used.

The present invention is used in steel mills, for example, and has the advantage that it can be used as a lifting device for one-dollar cranes.

In other words, the dollar crane is used for operations such as casting molten iron produced in a blast furnace or the like into a ladle, hoisting it up, and inserting it into a converter.

For example, if a dollar crane were to stop due to a failure, the entire steelworks would stop functioning and cause severe damage, so even if one part of the dollar crane were to malfunction, the operation could continue. It is necessary to provide equipment for this purpose.

A conventional method will be explained.

FIG. 1 shows the arrangement of the hoisting device of a conventional handheld crane, FIG. 2 shows its electric circuit, and FIG. 3 shows its characteristics.

As shown in FIG. 1, two electric motors 1 and 1' are used to rotate drums 3 and 3' via a speed reducer 2, thereby hoisting the load.

Further, the drums 3 and 3' are mechanically connected via a gear in a reduction gear, so that in the event that one electric motor fails, the remaining one electric motor can be used for emergency operation.

However, as can be seen from the electrical circuit and characteristics, in the conventional method, when performing emergency operation with one motor, the load applied to one motor is rated due to limitations in the heat capacity of the secondary resistor 9 or 10 and limitations in operating characteristics. I needed to keep it below.

In other words, in an emergency operation with the rated load lifted, 200% load is applied to one motor, so as shown in FIG. 3, the load torque becomes larger than the motor starting torque and the motor cannot be started.

For this reason, in conventional single-door cranes, (1) a planetary gear mechanism or mechanical reduction ratio switching device is installed in the reducer to reduce the hoisting speed to power when one electric motor is operating, and to Operate by keeping the applied torque below 100%.

(2) A method was adopted in which two cranes (one spare) were provided and if one broke down, another crane could be used.

The installation of such a reduction ratio switching device or a standby crane requires enormous equipment costs, requires extra space in the building or on the crane, and the device is complicated, making it extremely uneconomical.

Another disadvantage is that the switching device cannot be remotely operated for safety reasons.

The present invention has been made as a result of intensive research aimed at improving these drawbacks and has devised a method that allows emergency operation by electrically switching the circuit while using the current hoisting device even in an emergency.

In other words, emergency operation only requires that the motor be operated for a very short period of time (usually several minutes or less) and is rarely used if one electric motor fails.

In this way, it is noted that the emergency operation is a short-time operation, and even if the electric motor generates 200% torque for a short time, the temperature rise of the electric motor can be suppressed within the allowable range.

For this reason, during emergency operation, an electrical switching circuit is formed in which an electromagnetic contactor knife switch, etc. is attached to the secondary circuit of the AC wound induction motor, and the faulty motor is disconnected from the secondary resistor attached to the normal motor. By connecting the secondary resistors attached to the motor in parallel, we can overcome the limitations caused by the heat capacity of the secondary resistor, which was a problem during emergency operation with a single motor in conventional circuits, and furthermore, the speed-torque characteristics are shown in Figure 5. As shown, the starting torque of the motor is 2 even at 200% load torque.
This invention is characterized by being able to switch to a characteristic that allows the electric motor to start when the electric current exceeds 00%, allowing for easy emergency operation.

With the present invention, there is no need to provide a backup one-dollar crane or a reduction ratio switching device, which was conventionally provided, and it is possible to significantly reduce equipment costs and improve reliability.

An example of the present invention will be explained in detail based on the drawings.

As shown in FIG. 4, electromagnetic contactors 6, 7, and 8 are provided on the secondary side of the electric motors 1, 1' in addition to those in FIG.
．． 7. 8 is operated and controlled by a changeover switch 11 installed, for example, in a driver's guidance room.

In the case of normal operation, the selector switch 11 is set to the interlocking position and the electromagnetic contactor 4. 5. 6. 7 are respectively closed and the electromagnetic contactor 8 is opened to connect the two electric motors 1,
1' are operated in parallel.

However, in the unlikely event that one of the motors, for example motor 1, breaks down, it is necessary to carry out emergency operation using the normally operating motor 1'.

In this case, the selector switch 11 is switched to the dial M2, and this switch closes the electromagnetic contactors 5, 7 and 8, opens the electromagnetic contactors 4 and 6, electrically disconnects the motor 1, and closes the secondary resistors 9 and 10. Connect in parallel to electric motor 1'.

As a result, the resistance value of the secondary resistor becomes the length when the motor 1' is operating during normal operation, the heat capacity of the secondary resistor is doubled, and the characteristics become the speed-torque characteristics as shown in Fig. 5.
The same operation as normal is possible with the single electric motor 1'.

If a failure occurs in motor 1', contrary to the above,
By switching the changeover switch 11 to the dial M1, the electromagnetic contactors 4, 6, and 8 are closed, and the electromagnetic contactors 5, 7 are opened, and the normally operating motor 1 enters into independent operation with the characteristics shown in FIG. It is.

Note that the above explanation assumes that there are two electric motors and the case where one of them fails, but the number of electric motors is not limited to two, but can also be applied to three electric motors.
There may be more than one, and the number of failures among them is not limited to one, and emergency operation can be performed.

By configuring the operating circuit of the present invention in this manner, the following effects can be obtained.

(1) Safe and reliable emergency operation is possible by electrically switching the secondary resistance circuit.

(2) Since it can be switched electrically, remote control is possible and remote operation can be performed easily.

(3) The structure is simple and can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional operating state of multiple electric motors, Fig. 2 is a conventional circuit explanatory diagram, Fig. 3 is a conventional speed-torque characteristic explanatory diagram, and Fig. 4 is an explanatory diagram of the circuit of the present invention. FIG. 5 is an explanatory diagram of speed-torque characteristics. 1.1'...AC wound induction motor, 2...
...Decelerator, 3,3'...Drum, 4.5.
6.7.8...Magnetic contactor, 9,10...
...Resistor, 11...Selector switch.

Claims (1)

[Scope of utility model registration request] In a circuit that drives multiple AC wire-wound induction motors, an electrical switching circuit is created by attaching electromagnetic contactors, knife switches, etc. to the multiple motors and secondary circuits, and disconnects the faulty motor among the motors. , an emergency operation circuit for a multiple AC winding motor, characterized in that a secondary resistor attached to a normal motor and a secondary resistor attached to a faulty motor are connected in parallel.