Fault Example 9

Fault phenomenon: the equipment operates normally, and the DC current indication is on the high side. If the current is set at the rated value, the voltage is too low, and the indicated value of the power meter is inconsistent with the product of DC voltage and DC current, which is consistent before.

Fault analysis and treatment: the cause of the fault is that the indication of the DC ammeter is not accurate, giving people an illusion that the current is large.

The reason of this kind of fault in induction melting furnace is hidden and hard to find. If careful analysis, it can be found that the indicated value of power is not consistent with the product of voltage and current, indicating that the display value of the instrument may be wrong. The voltage value can be calibrated with the DC voltage of the multimeter, and the current value can be calibrated by measuring the incoming current with a clamp ammeter and dividing it by 0.816. If not, the ammeter indication is incorrect.

The value of the DC ammeter is taken from the 75mV voltage signal generated on the shunt. Under the conditions of long service time and harsh service environment, there is dirt or oxidation between the wiring on the shunt and the shunt, and the contact resistance increases, which increases the voltage generated on the shunt, which is greater than 75mV, causing the indication of the DC ammeter to be larger.

The treatment method of induction furnace is to deal with the dirt and oxide layer between the shunt and its wiring.

Yiphee Electric Furnace Co.,Ltd specializes in producing induction smelting furnace.Tel(WhatsApp):+86-13450756789, yiphee@yiphee.cn