Method for protecting frequency converter under high-current condition of separator

Abstract

A method for protecting a frequency converter under high-current condition of a separator comprises the steps that at least one air switch is connected between the frequency converter and a three-phase alternating current inlet wire in series, and before a deslagging electromagnetic valve is opened, a starting command of the frequency converter is cancelled; when the deslagging electromagnetic valve is opened, the frequency converter tends to stop decelerating, meanwhile, the PLC detects the running current of the motor, after the deslagging electromagnetic valve is closed and when the detected current is smaller than the rated current of the motor, the frequency converter is started again, and the frequency converter continues to run normally and accelerates to the rated rotating speed; a direct-current bus of the frequency converter is connected with the braking unit, the output end of the braking unit is connected with the braking resistor, when the motor accelerates and decelerates, energy feedback causes direct-current backflow voltage of the frequency converter to rise, and when the voltage rises to set voltage of the braking unit, the braking unit switches on the braking resistor. Impact of large current on the frequency converter is overcome through the frequency converter, the brake resistor and PLC control, and the frequency converter control system has the advantages of cost reduction, efficiency improvement and high safety.

Description

technical field [0001] The invention belongs to the technical field of frequency conversion equipment, and in particular relates to a protection method for a frequency converter under the condition of a large current of a separator. Background technique [0002] Today, with the rapid development of electronic technology, frequency conversion drive technology has been applied to all walks of life due to its advantages such as flexible start of equipment, wide range of speed regulation, and energy saving; The thyristor is used to change the DC into an adjustable frequency AC drive motor to achieve speed regulation. Since the inverter uses a thyristor, when the inverter drives the motor, the operating current must be within the rated current range of the thyristor (that is, the inverter rated current), when selecting inverters for some large-scale equipment, the inverter can only be selected by amplifying one gear, which will greatly increase the cost of use; Current fluctuati...

AI Technical Summary

Problems solved by technology

Due to the large weight of the drum, the large moment of inertia, and the fast running speed of the separator, in order to start smoothly, a large number of frequency converters are used to drive the separator. When starting, the frequency converter is controlled by the start-up time of more than 10 minutes to reduce the speed of the separator from zero. The speed is gradually pulled to full speed. After entering full speed, the solenoid valves are controlled by PLC in time sequence to achieve material separation. After each separation cycle, the slag will be discharged once. When the slag discharge solenoid valve operates, the current of the separator is particularly large, reaching the motor. The rated current is more than 2 times, but the time is shorter about 5~10S. At this time, the inverter will report an overcurrent fault and stop working. In some separators exceeding 55KW, the thyristor of the inverter will be burned directly, giving The normal operation of the separator has brought great challenges; some small power separators can directly increase the capacity of the frequency converter to solve the problem, but increasing the capacity of the frequency converter for high power separators will greatly increase the cost

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