For medium frequency power supplies matched with medium frequency furnaces, medium frequency power supplies below 1000KW generally adopt 380V, 50HZ industrial power of three-phase five-wire system, and are configured with 6-pulse single-rectification medium frequency power supply; that is, an ordinary power transformer is sufficient. For medium frequency power supplies above 1000KW, it is preferred to use input voltage above 660V (some manufacturers use 575V or 750V. Since 575V and 750V are non-standard voltage levels, spare parts are difficult to purchase, so it is not recommended to use them) and they are configured with 12-pulse double-rectification medium frequency power supply, which requires a 12-pulse transformer.

There are two purposes for selecting the input voltage of medium frequency furnaces

1. To increase the rated working voltage by raising the input voltage;

2. The harmonics generated by high-power equipment will interfere with the power grid. Double rectification can obtain a relatively flat direct current, the load current is a rectangular wave, and the load voltage is close to a sine wave, which reduces the impact of power grid interference on other equipment.

Do not blindly pursue high voltage

Some users blindly pursue high voltage (some use 900V input voltage for 1000KW equipment) and low current to achieve the purpose of energy saving. However, they do not realize that this comes at the cost of the service life of the electric furnace, and the gain does not compensate for the loss. High voltage easily shortens the service life of electronic components, causes fatigue of copper busbars and cables, and greatly reduces the service life of the electric furnace. In addition, for electric furnace manufacturers, high voltage design reduces raw material consumption and cuts costs. Medium frequency furnace manufacturers are certainly willing to do this (high selling price with low cost), and in the end it is the foundry end-users that suffer losses.