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　　Medium frequency Casting electric furnace What are the reasons for an abnormal startup? As a manufacturer of medium-frequency induction furnaces for casting, I’d like to show you the common causes of abnormal startup in these furnaces.

　　Phase failure in the rectifier: The fault manifests as abnormal noises during operation, with the output voltage rising significantly below its rated value. Meanwhile, the unusual noises emanating from the power cabinet become increasingly louder. At this point, you can reduce the output voltage to around 200V. By using an oscilloscope to observe the voltage waveform at the rectifier’s output, you’ll typically find that the input voltage waveform of a medium-frequency induction furnace has six distinct waveforms per cycle. However, when a phase failure occurs, two of these waveforms will disappear. You should use an oscilloscope to check the gate pulses of all six rectifier thyristors. If any gate pulses are missing, after shutting down the system, use a multimeter to measure the resistance across each gate resistor—specifically, the resistance between the gate and cathode terminals. Then, replace any thyristor that shows an open circuit or a gate resistor with exceptionally high resistance.

　　Variable-frequency drive three-phase operation: medium frequency Casting electric furnace After startup, the fault manifests as excessive output current and an empty furnace. Under the same operating conditions, the power supply cabinet produces significant noise. If you turn the furnace power knob to a lower setting, you’ll notice that the intermediate-frequency output voltage is much higher than usual. Using an oscilloscope to observe the voltage waveforms across the positive and negative terminals of the four inverter thyristors, you’ll find that when three bridge arms are functioning properly, the two adjacent thyristors in the inverter exhibit normal waveforms, while only the two adjacent thyristors lack waveforms—instead, the waveform of the other one is sinusoidal.

　　Induction Coil Failure: The induction coil of the medium-frequency furnace serves as the load for the medium-frequency power supply. It is made of square copper tubing with a wall thickness ranging from 3 to 5 millimeters. Common faults include leakage in the induction coil of the medium-frequency furnace, which can lead to arcing between coil turns and requires prompt repair and welding. Additionally, molten steel sticking to the induction coil can cause the steel slag to heat up and turn red, ultimately leading to damage and burning of the copper tubing; therefore, timely cleaning is essential.

　　So, how can we make medium-frequency induction furnaces for casting more energy-efficient?

　　The medium-frequency furnace can help develop good startup habits, significantly increase output power, and reduce the time required for heat preservation or baking. When the output power is not fully utilized, the power factor is low, resulting in higher losses.

　　Improving the utilization rate of medium-frequency furnace transformers also translates to energy savings. A 630 kVA transformer should be able to process 13 to 15 tons of molten metal within 10 hours. If you’re only handling 10 to 11 tons, your average electricity costs will be higher than theirs.

　　Research heating furnace baking, medium frequency Casting electric furnace By reducing the circulating cooling water flow through the induction coil and intermittently supplying power, the water outlet temperature can be maintained above 55°C, facilitating smooth steam discharge. This approach can shorten the operating time of medium-frequency induction furnaces. However, some medium-frequency induction furnace operators don't pay enough attention to this practice and instead maintain continuous power supply. As a result, the discharged steam encounters the copper pipes of the air-conditioning system, condensing into recirculating water. Consequently, the melting furnace operates longer, consumes more electricity, and delivers poor actual performance.

　　Alright, I wish everyone a happy life—see you next time!