News

① Inspection of Installation Conditions: Before commissioning, it is essential to thoroughly inspect for any desoldered joints and check for short circuits or contact between live conductors. Bare wires that are not at the same electrical potential must not come into contact with the furnace shell or other conductors. Ensure that the internal grounding wire is securely connected, and that the main grounding wire is firmly installed. The cross-sectional area of the copper core used for the grounding wire must be no less than 55 square millimeters. When measuring the resistance between the enclosure and ground on the ×1 resistance range, the reading should be zero. When three-phase incoming cables enter from the low-voltage switchgear, avoid any contact with the enclosure—especially do not allow the three-phase cables to rest against the enclosure in a bundled configuration, as this can lead to energy losses.

② Electrical Insulation Inspection: Before connecting the cooling water, the medium-frequency power supply should have its electrical insulation status of the entire system checked. For detailed instructions:

Before using a megohmmeter (commonly known as a "shake meter") rated at 1000V or 2500V to check the insulation of the main circuit and control circuit, the thyristors and printed circuit boards must be disconnected from the circuit. Connect one test lead of the megohmmeter to the enclosure of the medium-frequency power supply, and the other test lead to the busbar or control circuit; the measured insulation resistance should meet the insulation standards for industrial electrical equipment. Similarly, the insulation resistance between the enclosure of the medium-frequency heating capacitor, the induction heating coil, and the enclosure of the medium-frequency power supply must also comply with the required insulation standards. For components that have already been exposed to cold water, only the 1x range on a multimeter should be used to measure the insulation resistance. The insulation resistance of the main circuit in the rectifier section to the enclosure should be greater than 100 kΩ, while the insulation resistance of the main circuit in the inverter section to the enclosure should be greater than 30 kΩ. Water-cooled furnace switch, Induction coil, water-cooled cable The insulation resistance to ground should be greater than 10. The melting furnace should be tested only after the furnace lining has been dried.

③ Fastener Inspection: The medium-frequency power supply unit has a relatively large capacity. When operating under high current, if fasteners in the circuit become loose or disconnected, they can induce a high self-induced electromotive force in the circuit’s inductance, jeopardizing the safe operation of the main circuit and potentially damaging components. Therefore, it is essential to check the tightness of bolts at the connections of copper busbars—especially in the load circuit, where currents are higher, leading to greater heat generation during operation and subsequent expansion and contraction upon shutdown, which can easily cause fasteners to loosen. Many on-site failures are indeed attributable to these factors. When tightening the main terminals of medium-frequency capacitors, use two wrenches simultaneously and apply even pressure to prevent loosening at the weld between the terminal sleeve and the enclosure, which could lead to oil leakage and damage. In addition, all electrical connections—including fasteners and solder joints—should be thoroughly inspected.

④ Cooling Water Circuit Inspection: Check whether the flow of cooling water in various sections is unobstructed. Inspect the cooling water pipes, branches, and connections of components for any signs of leakage or seepage. Also, observe whether the plastic water pipes are bent, compressed, or otherwise deformed in a way that might impede the smooth flow of water. For medium-frequency power supplies, the water circuit connections should be arranged in series according to the principle of equipotentiality—especially when the water quality is less than ideal. If individual branches must be connected in series at different potentials, the plastic water pipes used for those branches should have a length of at least 1.2 meters. Leakage or condensation on thyristors can cause malfunctions; therefore, such issues must be promptly addressed and eliminated.