A 3-phase, 1500 KVA, 6600 v, star-connected alternator has 9 slots per pole and 6 conductors per slot. The output of this alternator on a particular load is given by 1200 KW and total losses of the machine is equal to 55 kW. What is the value of percentage efficiency?

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SSC JE Electrical 14 Nov 2022 Shift 3 Official Paper
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  1. 93.12
  2. 99.21
  3. 90.23
  4. 95.62

Answer (Detailed Solution Below)

Option 4 : 95.62
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Detailed Solution

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Rating of the alternator

An alternator is an electrical machine that converts mechanical input to electrical output.

The rating of an alternator always indicates the output electrical parameters.

The efficiency of the alternator is given by:

\(η = {Output \space power \over Output \space power\space + \space Losses}\)

Calculation

Given, Rating of the alternator: A 3-phase, 1500 KVA, 6600 V, 1200 KW

Pout = 1200 kW

Losses = 55 kW

\(η ={1200 \over 1200 + 55}\)

% η = 95.62

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