Frequency transformer, frequency control method thereof and crane

Abstract

The invention relates to a frequency transformer, a frequency control method thereof and a crane. The frequency control method comprises the following steps of S1, detecting whether a bus voltage at present is smaller than a slow-down operating voltage, going to step S2 to start a pressure-depended slow-down function if the bus voltage at present is smaller than the slow-down operating voltage, and going to step S4 if the bus voltage at present is not smaller than the slow-down operating voltage; S2, calculating a frequency according to the bus voltage at present, the calculated frequency being lower than a rated frequency of the frequency transformer, and operating by setting an output frequency of the frequency transformer at the calculated frequency; S3, detecting whether a bus voltage at present is larger than a normal operation voltage or not, going to step S4 to quit the pressure-depended slow-down function if the bus voltage at present is larger than the normal operation voltage, and going to step S2 if the bus voltage at present is not larger than the normal operation voltage; and S4 operating by setting the output frequency of the frequency transformer at a given frequency during normal power supply. The output frequency can be automatically adjusted according to the bus voltage conditions of the frequency transformer, thereby preventing security risks brought by reduction of output capacity of the frequency transformer.

Description

technical field [0001] The invention relates to the technical field of frequency converters, more specifically, to a frequency converter, its frequency control method and a crane. Background technique [0002] During the operation of the frequency converter, when the external power supply voltage drops, the output capacity of the frequency converter will decrease. If the frequency converter is still running at the given frequency, the frequency converter cannot guarantee to output enough torque. At this time, if the load of the frequency converter is very large, there will be a great potential safety hazard. Especially in the field application of the lifting industry, because there are generally many power frequency equipment on site, the peripheral power supply voltage is very unstable. When the power frequency equipment starts, the power supply voltage can suddenly drop from 380V to 300V or even lower. If the load carried by the crane is very large at this time, it will b...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to provide a frequency converter and its frequency control method and crane for the defect that the existing frequency converter still maintains the start-up given frequency operation and cannot guarantee to output sufficient torque when the power supply voltage drops.

Images