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At no load condition the generated voltage at transformer secondary output is 140 V ac. When a 60W resistive load is connected the voltage drops to 27 V ac. The pmg generator rating is 1 KW 415 V and transformer rating is 415/230 Vac 1 Kva. Why does the voltage drops so much and what would be the reason behind this scenario?

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  • \$\begingroup\$ Does rotational speed also lower? \$\endgroup\$
    – Andy aka
    Jan 19, 2015 at 8:51
  • \$\begingroup\$ Torque applied is maintain at constant for both scenario. But during the load condition there is a significant drop in rotation speed. It seems as the pmg got heavier. So to answer your question, yes the rotation speed is lower during load condition. @Andyaka \$\endgroup\$ Jan 19, 2015 at 8:57

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Torque applied is maintain at constant for both scenario. But during the load condition there is a significant drop in rotation speed.

If input torque is held constant then you are fashioning a constant current generator and not a constant voltage generator. Input mechanical speed would need to be held constant to produce a "near-enough" constant output voltage.

Mechanical power in = \$2\pi n T\$ where n is speed (rev/sec) and T is torque. You have kept T constant but allowed n to fall therefore the mechanical power into the generator has fallen just when you wanted power to increase!

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