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Question:

In the main circuit, the fuse and thermal relay thermal components can be less with one or two?

In the main circuit, the fuse and thermal relay thermal components can be less with one or two? Both the fuse and the thermal relay can only use one of them can play a short circuit and overload protection? why?

Answer:

Strictly speaking is not possible, because the thermal relay and fuse itself shoulder a different mission, thermal relay through the set of overload current overload protection, the principle is through the heat generated by the heat generated by the heat, the metal Deformation to achieve overload protection, for short circuit, the current is a sudden increase in the moment, the metal sheet too late to heat deformation, the motor has been burned. So the two are not the same effect.        As for the heating element and the fuse can be less or one or two of the argument is not correct, it is clear that the three-phase power which is not a phase of the motor is not rotating, the same less one or two protective components, Not can not use, but the lack of protection.
May 9, 2017
Hello, for the protection of the motor, requiring fuse + thermal relay with the use of the motor to play overload short circuit protection. Because the fuse only plays a short circuit protection, thermal relay only overload protection. Fuse three to be installed, if there is a phase is not installed, this phase if the occurrence of single-phase ground, will not play a protective role.
May 9, 2017
Thermal relay as an overload protection of the motor is necessary to be installed.
May 9, 2017

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