Why do fan motors burn out the drawer switch electrical components when starting?
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Our company has a centrifugal fan that was working fine the day before. With fair weather recently, when the control room was tried to be activated this morning, a fault was indicated immediately after activation. Upon going to the site and switching to manual mode, the operation indicator lights on the control panel worked as usual, lighting up and turning off, but the motor would not start. Checking the corresponding circuit breaker in the power distribution room, a strong burnt smell was detected; therefore, a spare circuit breaker was used, and an attempt was made to start the fan’s motor again. As soon as the motor started, it stopped, seemingly stuck (although it had rotated smoothly before). Immediately afterwards, the fault light on the circuit breaker came on. Upon inspecting the motor, it was found to be quite hot, with no other abnormalities or unusual smells. What’s going on here? Has the motor coil been broken down?
I. Power supply issues, such as burned-out fuses, aged or damaged circuit breakers, control circuit faults that prevent the contactor from engaging, or damaged contactors； II. Problems with the motor itself, such as short circuits between coil phases, grounding issues, seized bearings, or a broken rotor. III. An excessive load that causes the motor to become overloaded or even fail to start. Check them separately; basically, these are the reasons. At the moment of stall, the current increases by 5 to 7 times; in the case of Siemens motors, this increase can reach 11 times. Heat is generated as a result, and this leads to the burning out of the pull-out switch.
The fan motor was disassembled this afternoon, and it turned out that the coil was burned out. But another question arises: recently the weather has been sunny, and motors that were working fine the day before can burn out the next day. Could it be that a missing phase in the drawer switch causes a phase deficiency in the motor, leading to heat buildup and subsequent breakdown of the coils?