Sequence Three Phase Voltage Monitoring Relay 3A 250VAC Contact capacity

Phase sequence protector is a type of control relay that can automatically identify the phase relay protection relay, to ensure that some special mechanical and electrical equipment reversed due to the power phase sequence reversed and cause accidents or equipment damage. Such as elevators, central air conditioning, cranes, motors, etc. If the phase sequence of the power supply is wrong after repair, it will lead to accidents. The phase sequence protector must be connected to the control circuit to ensure the phase sequence is correct. Air-conditioner compressors also use phase sequence protectors to ensure that the compressor will not be reversed after maintenance.

working principle
Sampling three-phase power supply and processing, in the case of phase sequence of the power supply phase sequence and protector terminal input, the output relay is turned on, the device main control circuit is connected. The existing two types of products are: when the phase sequence of the power supply changes, the phase sequence does not match, and the output relay cannot be turned on, thereby protecting the equipment and avoiding the occurrence of accidents; the other type uses digital micro-core technology products and can realize automatic Phase sequence recognition, and automatic phase sequence conversion, to ensure that the motor rotates in a constant phase sequence.

The three-phase power supply is connected to the three connection points U, V, W (some R, S, T or L1, L2, and L3) of the protector in turn, and the auxiliary contacts of the phase sequence protector generally have a normally open and normally closed state. In the access control loop, it is connected normally or normally closed according to the control principle or wiring diagram. When the phase sequence is wrong or the phase is missing, the auxiliary contact action of the protector is normally open, normally closed, and normally closed. . If it plays a protective role, it should be normally closed contacts.

Phase sequence protector temperature protection
When the motor of the phase sequence protector does not exceed the rated value, the motor will overheat due to poor ventilation, high ambient temperature, and frequent startup times. In this case, the above over-current protection or overload protection cannot solve the problem, so a thermal protector that directly reflects the temperature change is needed.

Both temperature protection and overload protection use temperature to trigger protection, but not exactly the same. Overload protection is because the current exceeds the rated value for a long time to cause the relay to heat up and trigger protection; and the temperature protection is due to the poor heat dissipation, the overheating of the motor and the triggering of the protection. When temperature protection is triggered, the current value in the motor may be normal, so overload protection does not necessarily work. Temperature protection and overload protection can not be replaced with each other.

♦ Technical data