(a) What are the factors which determine the synchronous speed of a motor?
(6)
(b) A twelve-pole, three-phase, delta connected alternator runs at 600 rev/min and supplies a balanced star connected load. Each phase of the load is a coil of resistance 35 ohm and inductive reactance 25 ohm. The line terminal voltage of the alternator is 440V. Determine
(10)
(i) frequency of supply,
(ii) current in each coil,
(iii) current in each phase of the alternator,
(iv) total power supplied to the load.
Reference Answer
### (a) Factors Determining Synchronous Speed The synchronous speed of an AC motor (both synchronous and induction types) is the speed at which the magnetic field of the stator rotates. This speed is constant for a given motor design and supply condition and is determined by two fundamental factors: 1. **Supply Frequency (f):** * **Relationship:** The synchronous speed is directly proportional to the frequency of the AC electrical supply.
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