Answer / atul naik

Its not 100% true. Actually Motor has been protected many
a times before it actually burns. But either we have
ignored the actual reason of tripping by resetting OL
Relay or by removing the Over Load on Motor.
Still Motor Burns. So it is observed that following reasons
are there. 1 Dips in Supply Voltage, 2 Frequent Over Loads
reduces the performance/ sensitivity of OL Relay 3 Short
Ckt Protection is Not there (ANSI 50 & 50N )4 Short Ckt
Protection is Not Fast or delayed ( to avoid Nusence
tripping in Starting )5 Impairing of an Insulation due to
entry of unwanted gases,liquids etc,Reducing the Insulation
Strength of the Motor.,6 Wornout bearings, it will not only
oppose the motion and create resistance but also it
increases the heat / temp. 7 In case of CT Operated
Relays , CTs may reduce senstivity. Now, the cumulative
effect is that Fault Clearing Time is More than the Temp
rise time due to Fault , due to which Motor insulation
fails and motor winding no longer remain healthy ie Motor
burns.

I have a 3 phase 600 volt prim. feed and a 120/208 sec. Isolateing tranformer .We are using this system for safety against shock . What is the proper grounding ?? Does the common on sec. get earth ground ???

1 Answers  

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Why in medium voltage system(3.3kv to 33kv, neutral is earthed with either resistance, reactance or neutral grounding resistance?

4 Answers   Essar,

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What is type of transformers?

3 Answers  

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6 Answers   GIL,

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I am getting above 60 V as open delta voltage against single phase unit ICT at tertiary delta formed and ICT getting trippped on NDR. ICT tested and found in order. PTs provided on tertiary are tested and in order. what may be the reason?

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During FEED, you will have all the information with regards to cable. How will you calculate the MTO for MV and LV Cables? what are your considerations?

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what type of transformer used in soft ware parks its distribution or power transformer. like 1800 kva

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What are motor generator sets and explain the different ways the motor generator set can be used ?

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Which level of the Transformer oil got dielectric strengh? And why?

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What is main difference between earthing and neutral grounding?

3 Answers   Jindal,

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