transformer Overvoltage overcurrent protection devices _PTC thermistor
Over-current protection is when the transformer in the work of its current exceeds the rated current, Make transformer protection circuit automatically disconnect the circuit. Simply put, when the transformer current exceeds a certain value, The protection circuit will automatically cut off the power transformer, Thereby protecting the transformer from excessive current damage.
Application principle as shown below: The PTCR series in the transformer primary circuit, When the circuit is in normal working condition, The current through the PTCR does not exceed the rated current that does not exceed the PTCR maximum non-operating current. PTCR in the normal state, the resistance is small, Will not affect the normal operation of the protected circuit. When the circuit fails, The current greatly exceeds the rated current, PTCR sudden fever, High impedance state, So that the circuit is relatively "off" state, To protect the purpose. When troubleshooting, PTCR automatically resume normal work.
Transformer over-current protection is installed in the transformer on the secondary circuit. Such as three-phase transformer overcurrent protection: When any sideof the transformer bus short-circuit fault occurs, Overcurrent protection action. Because the three sides are equipped with over-current protection, Enabling it to selectively remove the fault. Without having to shut down the transformer. Overcurrent protection on each side can be used as the side of the bus, Line backup protection. The overcurrent protection on the main power side can be used as back-up protection for the other sides and the transformer.
Transformer overcurrent PTC thermistors schematic