is the back emf same as that of the potential applied to the motor?
2007-09-17 00:49:58 · 3 answers · asked by Premnath V 1 in Science & Mathematics ➔ Engineering
Back EMF may be used in braking . So if you consider stopping as useful work then Yes back EMF is useful...
As far a Back EMF equality, there are always losses and these also apply to back EMF. Consider if the Force to turn a generator were met with an equal and opposite back EMF force then the shaft wouldn't turn as one force would cancel the other out.
2007-09-17 09:05:55 · answer #1 · answered by MarkG 7 · 1⤊ 0⤋
Back EMF is always less then the applied voltage but is directly relative to RPM, hence a motor uses less current the faster it spins and more current as increased load slows it down. If you stall the motor you have zero back EMF and the motor usually starts to smoke. Back EMF is used to recover power in electric vehicles, to top up batteries in cars or return power to the grid in trains. Some auxillary braking systems on coaches use purely back EMF systems ( the generated power is dumped through a heater),to reduce the brake fade in friction brakes, usually referred to as an "electric retarder" as it cannot brake you to stop. Used on long down hill gradients.
2007-09-17 01:47:03 · answer #2 · answered by terryrow 2 · 2⤊ 0⤋
No. If it were, no current would flow.
2007-09-17 01:21:12 · answer #3 · answered by amania_r 7 · 1⤊ 1⤋