JPS5940747B2 - Bucket crane speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for a packet crane using a wound induction motor as an opening/closing motor for opening and closing a packet and a supporting motor for hoisting and lowering the packet.

Figure 1 shows the configuration of a conventionally known packet crane.

In the figure, 1 is a support motor that hoists and lowers the packet 11, 2 is an opening/closing motor that opens and closes the packet 11, 3 is a brake for stopping and holding the support motor 1, 4 is a brake for the opening/closing motor, and 5 and 6 are respectively The support and opening/closing reducer 7 is a winding drum for the support rope 9, 8 is a winding drum for the opening/closing rope 10, and 11 is a packet sustained by the support rope 9 and the opening/closing rope 10.

Next, the operation will be explained.

First, when closing the packet 11, the opening/closing motor 2, the opening/closing rope 10, the opening/closing drum 8, with the support motor 1 stopped.
By rotating in the winding direction, the packet 11 performs a closing operation.

On the other hand, when opening the packet 11, the opening/closing motor 2 rotates in the direction in which the opening/closing rope 10 is paid out.When winding up the packet 11, the opening/closing motor 2 rotates in the direction in which the opening/closing rope 10 is fed out. By rotating the ropes 9 and 10 in the winding direction, the packet 11 can be rolled up.

Further, when lowering the packet 11, the lowering operation is performed by rotating the supporting motor 7 and the opening/closing motor 8 together in the supporting and opening/closing ropes 9, 10 in the direction of letting out.

Among the above operations, the operation of lowering the packet 11 in an open state will be described in detail.

In the open state of the packet 11, most of the weight of the packet 11 is applied to the support rope 9, and the support brake 3
When released, the support motor 1 can start rotating due to the weight of the packet 11.

On the other hand, the tension in the opening/closing rope 10 is very small when the packet 11 is open.

In other words, when the packet 11 is opened and lowered, the support motor 5 is under a negative load, and the driving force is the same as that of the packet 1.
In order to control the speed, it is possible to control the speed by adjusting only the braking force generated by the support motor 5.

Further, the opening/closing motor 2 is under almost no load, and large driving torque and braking torque are not required.

When opening and lowering is performed in such a state, the supporting motor 1 is generally accelerated by the load, so the speed becomes faster than the opening/closing motor 2, and the packet gradually tends to close, resulting in poor work efficiency.

This invention has been made in view of these points, and provides a packet crane speed control device that can operate both electric motors at approximately the same speed during opening and lowering, where the load sharing between the supporting motor and the opening/closing motor is extremely different. This is what we provide.

An embodiment of the present invention shown in FIG. 2 will be described below.

In the figure, 1 is a support motor, 2 is an opening/closing motor, 3 is a finger speed generator mechanically connected to the support motor, and 4 is a comparison of the speed command and the speed of support motor 1 to determine the firing angle of thyristor 5. an automatic control device that adjusts the DC voltage applied to the support motor 1 and controls the speed of the support motor 1; 6 is a diode for smoothing the DC voltage flowing to the support motor 1; 7;
is a secondary resistor for the switching motor, 8 is a secondary resistor for the support motor, 9 is a three-phase AC power supply 11 to 17 and 21 to 24.31
34 is an electromagnetic contactor, 41 is a support brake, and 42 is an opening/closing brake.

Next, the operation when opening and lowering the packet is shown in Figure 1.
This will be explained using FIG.

At the time of opening and lowering, the electromagnetic contactors 13, 15, and 16 are closed, and the contacts 11, 12, and 17 are released.

In this state, when the brakes 41 and 42 are released, the support motor 1 starts rotating in the direction of letting out the support rope 9 due to the weight of the packet 11 mentioned above.

Here, the thyristor 5 is configured to be controlled by the automatic control device 4 so that it has a conduction angle of a certain amount or more regardless of the relationship between the speed command, the speed from the finger speed generator 3, and the feedback. A DC current exceeding a certain value is flowing through the support motor-secondary winding.

Therefore, when the support motor 1 starts rotating, a three-phase AC voltage proportional to the rotation speed of the support motor 1 is obtained in the support motor secondary winding.

However, the frequency induced in the secondary winding is expressed as f2 - support motor secondary winding induced frequency N = support motor rotation speed No - support motor periodic rotation speed f = power supply frequency.

By short-circuiting the primary winding of the switching motor 2 in addition to the secondary winding of the switching motor 2 using this three-phase AC voltage, the switching motor 2 rotates at the frequency generated by the support motor 1 at a synchronous speed. .

Further, as described above, since almost no load torque is applied to the opening/closing motor 2, it rotates with almost no slippage and rotates following the speed of the support motor 1.

For speed control, the firing angle of the thyristor 5 is controlled by the automatic control device 4 in accordance with a speed command for the speed of the support motor 1, thereby enabling operation from low speed to high speed exceeding the synchronous speed of the motor.

If the DC excitation current of the support motor 1 becomes too small, the switching motor 2 may be unable to follow it or may become unable to follow it.

In order to prevent this, a minimum DC excitation current is set in the automatic control device 4 so that the DC excitation current does not fall below that value.

As described above, according to the present invention, when the packet is opened and lowered, the opening/closing motor rotates at a synchronous speed with the frequency generated by the supporting motor, so that both the supporting and opening/closing motors are driven at almost the same speed by only controlling the speed of the supporting motor. This has the effect of improving work efficiency as the packet can be lowered without being closed like in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a packet crane, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a support motor, 2 is a switching motor, 3 is a finger speed generator, 4 is an automatic control device, 5 is a thyristor, 6 is a diode, and 11 to 11 are electromagnetic contactors. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. The above-mentioned lowering of a packet crane having a first wound-type induction motor that hoists and lowers the packet, and a second wound-type induction motor that opens and closes the packet and has the same number of poles as the first wound-type induction motor. When the primary winding of the first winding type induction motor is connected to a DC power source and the secondary windings are respectively connected to the secondary windings of the second winding type induction motor, The means for short-circuiting the primary winding between the terminals is a speed detector for detecting the speed of the first induction motor, and the output of this speed detector is compared with the speed command ♂, and the output of the DC power source is adjusted according to this comparison value. a control device that maintains the output of the DC source above a set value sufficient to control the output and maintain a tracking relationship between the first and second motors; According to the second above
A speed control device for a packet crane, characterized in that it controls the speed of a wound induction motor.