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Protection Functions Of SJR3 Softstarter

Jul 24, 2019

SJR3 series soft starter pocesses complete protection functions to protect the operation security of the soft starter and the motor. During operation, the protection level and protection parameters should be properly set based on different circumstances. 

■ Over-heating protection of the soft starter: the protection will start when the temperature rises to  80℃±5℃, and it will stop when the temperature falls to 55℃(lowest).

■ Delayed time of input phase loss protection: <3s.

■ Delayed time of output phase loss protection: <3s.

■ Delayed time of input three-phase unbalance protection:<3s. Taking the deviation of current in each phase is over 50%±10% as the criteria, when the load current is less than 30%

of the nominal rated value of the soft starter, it is confirmed that the deviation will increase. 

■ Protection time of over-current during starting: the protection time shall be continued to be longer than 5 times of the maximum operating current of code F5.

■ Protection time of overloading in running: inverse time limit thermal protection shall be provided based on the maximum operating current of code F6.

■ Delayed time for power under-voltage protection: when the power voltage is under the extreme value 40%, the protection time<0.5s, when the power voltage is over the set value, the protection time<3s.

■ Delayed time for load short circuit protection <0.1s, if the current is more than 10 times of the nominal rated value of the soft starter, this protection shall not replace the fuse or short circuit protection device. 

The above time parameters are the periods from the valid signal being detected to the tripping protection directive being given;these parameters are for information only. In the event that the protection functions of the ac motor soft starter fails to meet the requirements of customers, special protection devices should be installed to ensure the safety. 

SJR3 Series Softstarter