Hi there, Can you please assist? 1. Analyze the probable cause of the following

Question

Hi there,

Can you please assist?

1.               Analyze the probable cause of the following problems in motors and suggest remedial measures:

a.       A motor driving a pump often fails to start and trips with indication of overload. The electrical parameters are normal. The observation is that every time this happens the delivery valve is fully open.

b.      The motor driving a rotary cement kiln fails repeatedly and every time the insulation is found to have burnt out. It is observed that this happens only during summer when the temperature is close to 45 Deg C.

c.       A compressor motor being switched on for the first time rotates in the reverse direction.

d.      A bulk ore handling conveyor motor has repeated failures. After repairs the motor runs normally for a few months till it again suffers a burn out. It is a totally enclosed fan cooled motor and every time it fails it is observed that the outer fins have a thick and hard deposit of ore dust.  

Explanation / Answer

a. suction rate becomes equal to delivery rate. Suction should be more than delivery. b.due to much heat production, insulation cant withstand much heat. Insulation can be changed. c. it rotates in reverse direction in order to suck air from atmosphere. d. It fails and outer fins have a thick and hard deposit of ore dust because, its life is shorter, moreover due to centrifugal force it has thick and hard deposit of ore dust on outer fins.

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