Analysis and treatment of common faults of medium frequency electric furnace equipment
Medium frequency electric furnace equipment is widely used in iron and steel, casting, special steel and other related fields. Different application fields have different requirements for medium frequency electric furnace equipment. Only on the basis of mastering the basic working principle of these circuits and the basic characteristics of power devices, can we quickly and accurately analyze and judge the cause of the fault, and take effective measures to eliminate the fault What common faults do you have? Please enjoy the explanation below.
1. Start up, if electric furnace equipment cannot be started normally
Fault phenomenon: large DC current, low DC voltage and if voltage when starting, dull equipment sound.
Analysis and treatment: the thyristor with one arm of the inverter bridge may be short circuited or open circuited, resulting in the operation of the three arm inverter bridge. Use an oscilloscope to observe the voltage drop waveform of the thyristor on the four bridge arms of the inverter bridge. If the voltage drop waveform of the thyristor on one bridge arm is a line, the thyristor has been through; if it is a sine wave, the thyristor has not been through. Replace the through thyristor; find out the reason why the thyristor is not turned on.
2. The equipment can be started, but the working state of medium frequency electric furnace equipment is not correct
Fault phenomenon: the equipment can be started normally and smoothly. When the power rises to a certain value, overvoltage or overcurrent protection will be provided.
Analysis and processing: find out the fault cause in two steps:
1) first operate the equipment without load, and observe whether the voltage can rise to the rated value. If the voltage cannot be raised to the rated value, and over-current protection is carried out near a certain value of voltage for many times. This may be caused by insufficient compensation capacitance or thyristor voltage, but it is also caused by ignition of some part of the circuit;
2) if the voltage can be raised to the rated value, the equipment can be put into heavy load operation, and observe whether the current value can reach the rated value. If the current cannot be raised to the rated value, and the overcurrent protection is conducted near a certain value of the current for many times, this may be a large current interference. Special attention should be paid to the interference of the electromagnetic field of the medium frequency and large current to the control part and the signal line.
3. Faults easy to occur during normal operation of medium frequency electric furnace equipment
Fault phenomenon: the equipment operates normally, but when the normal overcurrent protection acts, several KP thyristors and fast melting are burned.
Analysis and treatment: during overcurrent protection, in order to release the energy of smoothing reactor to the power grid, the rectifier bridge changes from the rectifier state to the inverter state. At this time, if a > 1500, it may cause the active inverter to overturn, burn down multiple thyristors and fast melting, and the switch trips, accompanied by a huge current short-circuit explosion. It has a great impact on the current and electromagnetic force of the transformer, which will damage the transformer seriously.
The above three points are the common faults of medium frequency electric furnace equipment and the methods of analysis and treatment. If you want to understand other problems, please pay attention to the dynamics of this website.