Permissible Limits for Variations in Electrical Machine

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Permissible Limits for Variations in Electrical Machine

Q. State the permissible limits for variation of : 1) Voltage 2) Current 3) Speed 4) Frequency.

Permissible Limits for Variations

  1. Voltage variation should not be ±5% of rated voltage.
  2. Current should not exceed rated current.
  3. Temperature rise should be within limits.
  4. Frequency should not vary by ±1 of rated frequency.
  5. Should work within ±2% of rated speed.
  6. There should not be magnetic locking for 3 phase induction motors.
  7. Uniform air gap between static and rotating part.
  8. Perfect bearings, no play.
  9. No dust-dirt moisture deposition.
  10. No noise, quiet operation.

If the above conditions are fulfilled the machine is said “running normal”.

But doe to various reasons, faults are developed in the machine and it gives trouble in working Its working is not satisfactory.

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