JPH05207778A - Speed controller for crane - Google Patents

Abstract

PURPOSE:To achieve a high speed change ratio without causing the deficiency of torque in inverter control. CONSTITUTION:An induction motor 11 drives a crane through frequency control of an inverter 12. A controller 14 controls a pole number converter 16 based on a signal detected through a speed designating generator 15 directly coupled with the induction motor 11. In other words, the number of pole of the induction motor 11 is designated to six in low speed region while to four in high speed region. Consequently, speed can be increased in high speed region without causing the deficiency of torque and a high speed change ratio can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the speed of a crane by controlling an inverter.

[0002]

2. Description of the Related Art Conventionally, there is known an automatic warehouse having a unit type rack, in which a stacker crane travels in a passage between rack rows to load and unload cargo from the rack. To control the traveling speed of such a stacker crane, a method of controlling the speed by changing the frequency of the voltage applied to the motor terminal for driving the crane is adopted. That is, speed control is performed by controlling the frequency of the voltage supplied to the electric motor by the inverter.

[0003]

However, in speed control by frequency conversion using such an inverter, torque is insufficient in a low frequency region and a high frequency region even if an attempt is made to increase the gear ratio of the electric motor. There was a problem that it would end up. For example, in the case shown in FIG. 3, it is difficult to obtain a gear ratio of 1:20 or more because the torque sharply drops at 3 Hz or less and 60 Hz or more. That is, in the conventional inverter control, even if an attempt is made to increase the gear ratio, the torque becomes insufficient in the low frequency region and the high frequency region.
There is a problem that a high gear ratio cannot be obtained.

The present invention has been made in order to solve the above-mentioned conventional problems, and provides a speed control device for a crane capable of obtaining a high gear ratio without causing a torque shortage in inverter control. It is a thing.

[0005]

A speed control device for a crane according to the present invention is a speed control device for a crane, which is provided with an inverter for supplying a frequency-controlled output voltage to a motor for driving the crane. It is characterized in that it comprises a pole number converting means for converting the number and a control means for controlling the pole number converting means so that the number of poles in the high speed region is smaller than that in the low speed region.

[0006]

By the control means, the number of poles of the electric motor in the high speed region is smaller than that in the low speed region. As a result, it becomes possible to further increase the speed without causing a torque shortage in the high speed region, and as a result, it is possible to increase the gear ratio.

[0007]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing a speed control device for a crane according to this embodiment. The speed of the stacker crane (not shown) is controlled by the induction motor 11. The inverter 12 is connected to a power source via a breaker 13, and is controlled by a controller 14 to change the frequency of the voltage applied to the induction motor 11 and control the rotation speed (speed) of the induction motor 11. A finger speed generator 15 is directly connected to the induction motor 11, and the speed of the induction motor 11 is detected by the finger speed generator 15. The controller 14 controls the pole number converter 16 based on the speed of the induction motor 11 when the induction motor 11 is driven,
In the low speed region, the number of poles of the induction motor 11 is relatively increased,
In the high speed region, the number of poles is relatively small.

FIG. 2 shows the speed characteristics of the induction motor 11 that drives the stacker crane. As shown in this figure, when the induction motor 11 is driven, the pole number converter 16 converts the pole number of the induction motor 11 under the control of the controller 14. That is, the number of poles of the induction motor 11 is 6 in the low frequency region (low speed region) below the rated frequency (60 Hz) at point a.
, And at point a (high-speed region), it is set to 4.

As described above, the induction motor 11 is driven by the number of poles 6 at 60 Hz or less, and the speed ratio of speed control by frequency conversion based on inverter control is 1:20. When the frequency rises and reaches 60 Hz, the number of poles of the induction motor 11 is converted from 6 poles to 4 poles, whereby the speed V ₁
Is about 1.5 times the speed Vo when the pole number conversion is not performed. That is, the speed ratio for speed control is 1:30.
Therefore, a high gear ratio, which cannot be obtained only when the inverter is controlled, is obtained, and the induction motor 11 operates in the high frequency range.
The speed of the stacker can be significantly increased and the stacker crane can be operated at high speed.

The frequency at which the number of poles of the induction motor 11 is changed is not limited to 60 Hz, and an appropriate value can be set according to the purpose. Also, the number of poles to be changed can be set to an appropriate value according to the purpose.

[0011]

As described above, according to the present invention, in the inverter control, it is possible to obtain a high gear ratio without causing a torque shortage.

[Brief description of drawings]

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

FIG. 2 is a diagram showing speed characteristics in the embodiment of FIG.

FIG. 3 is a torque characteristic diagram during speed control based on frequency control of a conventional example.

[Explanation of symbols]

 11 induction motor 12 inverter 14 controller 15 finger speed generator 16 pole number converter

Claims (1)

[Claims] 1. A speed control device for a crane comprising an inverter for supplying a frequency-controlled output voltage to an electric motor for driving a crane, comprising: a pole number converting means for converting the pole number of the electric motor; A speed control device for a crane, comprising: a control means for controlling the pole number conversion means so that the number of poles is smaller than that in a low speed region.