Answer / surajit mishra

A Circuit Breaker is often required to operate when there is no power. If the auxiliary power in a station is taken for the Main power supply, the CB Trip coil and closing coil will not have power to operate. The CBs have Closing Coil for switching On and a Shunt Trip coil for switching off. In substations, DC Control supply, usually 110V DC, from Lead Acid Battery sets are maintained to provide DC supply for operating the Closing Coil and Trip Coil. Not only MV Breakers, if the system requires even an LV Breaker to operate when mains power is not available, DC Control supply is used.

how we can improve power factor from 0.8 to 0.85 or 0.9 & how we identify its either lag or lead ? thank you

7 Answers  

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in a 740 kw dc seperately excited motor field voltage is constant about 17.4 volts and armature voltage is500 volts dc. how it is possible to have two different voltages from single transformer of output voltage 500 volts? if any difficulty in question contact ajitsingh.kadian@gmail.com

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What are instrument transformers?

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I HAVE A INCOMING 100A MCCB TPN 25KA, CABLE LENGHT OF 80M 70MM CABLE SIZE FROM MAIN SUBBOARD TO NEW DB.BASE ON THE FAULT LEVEL SETTING OF 45KA.I WOULD LIKE TO FIND OUT 25KA ENOUGH KA. APPRECIATE IF SOMEBODY CAN ASSIST ME WITH FORMULA FOR THIS. FRM: JEFF

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-What shall be short circuit current of LV switchgear for a 1000 kva, 11.415kv, 3 phase tranformer with 5% reactance.

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How to calculate the Short Circuit Impedance in Transformer?

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how to calculate the torque of a motor?

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What is the significance of 3.5 core cable ????

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WHAT IS MOBILE SUB-STATION? & REALLY BENEFIT IN INDIA

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Are we do it in single transformer with dual primary as 11 KV and 33 KV and constant output as 415 Volts?.

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how to find insulation resistance of a generator(11kv) by theoritical formula??

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The basis on which voltage selection of motor is done i.e. either HT or LT.

1 Answers   DAE,

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