Permissible Limits of Variation of Supply Voltage to Motor and Variation of Frequency
Q. Give the permissible limits related to terminal voltage, frequency, temperature rise and speed variation for safe working of electrical machines.
Permissible Limits of Variation of Supply Voltage to Motor and Variation of Frequency :
- The performance of Electric Machines particularly working on A.C. supply depends on voltage and frequency variations.
- It is expected that the machine shall be capable of delivering rated output at the rated power factor within the variation of voltage limit of + 5% 10 – 5% and frequency variation easy solution between + 1% to – 1% and in such variations the temperature shall not exceed more than 5°C.
- The variation of voltage and frequency beyond these limits affect the performance of the machine. Variation in speed is limited to 2% for D.C. machine and 3% for A.C. motors from synchronous speed from no load to full load.