Variable frequency control circuit and control method for electric hoist

Abstract

The invention relates to a variable frequency control circuit and a variable frequency control method for an electric hoist. The control circuit consists of a power supply unit and a monitoring unit, which are connected. A three-phase alternating current power supply supplies low-frequency three-phase alternating current power to a hoisting motor through a low-frequency three-phase alternating current power supply branch to realize the low-speed running function of the hoisting motor, and supplies high-frequency three-phase alternating current power to the hoisting motor through a high-frequency three-phase alternating current power supply branch to realize the high-speed running function of the hoisting motor. The control method comprises a switching control method for the low-speed running to high-speed running of the hoisting motor and a switching control method for the high-speed running to low-speed running of the hoisting motor. The circuit and the method have the characteristics of rational design, low cost, high reliability and the like, and can be widely applied in the field of motor driving and control for hoisting machinery; and the requirements of the electric hoist on speed control and safe running are met.

Description

technical field [0001] The invention belongs to the field of drive and control of hoist cranes, in particular to an electric hoist frequency conversion control circuit and a control method thereof. Background technique [0002] When the hoist crane (electric hoist) is working, in order to facilitate the hoisting and accurate positioning of heavy objects, it needs to have two operating speeds, fast and slow. At present, in order to realize the double-speed function, the hoist crane usually adopts the following two speed change control methods: one is to use a double-winding motor or a master motor. The disadvantage of this method is that it must be equipped with two sets of gear speed change mechanisms. High rate. The second is to directly equip the general-purpose frequency converter on the single-speed hoisting motor to realize fast and slow running functions. Its advantage is that it can flexibly realize stepless speed change. Huge braking resistor, the braking resistor ...

AI Technical Summary

Problems solved by technology

At present, in order to realize the double-speed function, the hoist crane usually adopts the following two speed change control methods: one is to use a double-winding motor or a master motor. The disadvantage of this method is that it must be equipped with two sets of gear speed change mechanisms. high rate

The second is to directly equip the general-purpose frequency converter on the single-speed hoisting motor to realize fast and slow running functions. Its advantage is that it can flexibly realize stepless speed change. Huge braking resistor, the braking resistor has a large volume and is very difficult to install. At the same time, because the inverter itself generates a lot of heat, it is necessary to open cooling vents on the electrical control box, which reduces the IP protection level of the box.

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