Harmonic control of medium frequency furnace

The user’s main load is an medium frequency furnace for smelting, which mainly produces castings such as motor casings. A 400kVA, 10kV/0.4kV transformer is used for power supply.

1. According to the actual measurement on site, the actual electricity consumption of users is as follows: under no-load conditions, the voltage on the user side is 250V; under full load, the voltage on the user side is 235V; under full load, the electrical power used is 600kW; under full load, the electrical power used is The factor is 0.97 ahead; when operating at full load, the current consumption is 910A.
2. Harmonic control equipment, using the medium frequency furnace harmonic control of Science and Technology Electric for harmonic control. Its main technical indicators are: the maximum compensation current can be 400A; the rated voltage is 200/380V; the effective output power is 100kVA; the DC side bus voltage is 450VDC; the switching frequency is 10kHz. For the power quality before and after the harmonic control, the harmonic meter was used to measure the various operating states of the medium frequency furnace, and the meter data of the user power distribution cabinet was read at the same time, from the start of the equipment to the full load operation of the equipment.
3. Situation analysis: As the transformer is overloaded, voltage distortion is caused, and harmonics are also greatly increased; in addition, the control of six-pulse phase rectification makes the current change rate of the thyristor in the commutation process extremely large, and the waveform of the entire load presents a right angle The rate of change, the form factor is poor, and the harmonic distortion is serious. When the power factor cannot meet the requirements, it is only caused by poor form factor, and conventional reactive power compensation equipment cannot be used for compensation.