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In recent years, with the continuous development of frequency conversion technology, the performance of VFD has been increasing day by day. The variable frequency speed control’s properties is hard, the speed regulation range is large, the speed regulation precision is high, the stability is good, the control is easy, and the energy saving is efficient. It can meet the safe, stable, reliable, operability, reliability and maintenance-free requirements of the lifting equipment, and quickly achieve a breakthrough  and be widely used in the crane industry.

At present, among many VFD brands, there are not many products that can fully meet the needs and characteristics of the crane industry. The main difficulty is that due to the particularity of the cranes, the VFD for the cranes must have some special performance: quick dynamic response to meet the demand for drastic changes in crane loads; wide range of speed control capability to enable the motor to output 2~3 times the rated output peak torque of the rated torque in the vicinity of the low speed section; withstand the shock of current caused by the drastic change of potential energy load and ensure reliable operation under continuous mechanical vibration environment; the regenerative energy of the motor should be reliably released when the brake is decelerated, and the current capacity of the brake unit needs to be larger; have a high reliability protection system. For the lifting mechanism, special attention should be paid to the control of the slip hook after the mechanical brake is released or before the brake is held; have a powerful monitoring system. The system fault alarm and fault analysis can be achieved by monitoring various parameters.

Take the Delta VFD-C2000 VFD for an example, this paper briefly introduces how to solve these difficulties. The FOC PG control application of Delta VFD-C2000 VFD can obtain stable speed output and optimal dynamic response through motor parameter learning function and speed feedback signal. The output torque can be precisely controlled within a wide range of 0.05hz to 50Hz. The current capacity is large enough to withstand up to 200% of rated current impact; has a unique energy recovery technology; has a perfect protection system with stalling protection function, which can prevent the stalling problems in acceleration, deceleration and operation, and also has overcurrent, overvoltage, undervoltage and input phase loss protections, as well as overtemperature, overload, overspeed, motor fault protections and other functions. The C2000 has a built-in PLC function and a CANopen protocol, and can complete real-time data monitoring by cooperating with high-speed communication networks such as Modbus, Profibus and DeviceNet. With the continuous development and improvement of power electronics technology, VFDs in the crane machinery industry are increasingly showing excellent control and speed regulation performance, high efficiency, easy maintenance, etc. Combined with the continuous decline of VFD prices, variable frequency speed control of motor will become a kind of hoisting machinery optimization control scheme, the market size of VFDs in the crane machinery industry will continue to expand.