Motor and alternator in same shaft

[vadali]

Sir,
Should we make both Motor and Alternator on same shaft?
the Motor will run at 12V and it should not consume >2 Amps and tha same time Alternator should produce 220 V 300watts.

Please reply

 

[elegysix]

not sure what you mean by running them on the same shaft... but if you mean to have the alternator power your motor, hooking up 220V directly to a 12V motor will destroy it... you'd need a transformer to drop the voltage and be able to provide enough current.

 

[rcgldr]

The motor will consume more power than the generator outputs, so it's not a perpetual motion machine. Similar devices are used in some power supplies, relying on the momentum of the motor to provide "cleaner" output to mask variances in the input power. Large ones were used on old mainframes:

http://smud.apogee.net/comsuite/content/ces/?utilid=smud&id=1586

There are some audiophile power conditioners still being made using motor + altenator (called power regenators), but I don't know if this is more of a gimmick method than a pratical one.

 

[Drakkith]

A motor consuming 12 volts and 2 amps would NOT produce 300 watts from an alternator attached to it. It would at best produce 24 watts, and realistically produce less thanks to losses.

 

[FireStorm000]

Ultimately, it comes down to conservation of energy, as drakkith said. Power is Voltage times current, so a motor running on 12V 2A consumes 24W of power. A generator powered by that motor (and that motor alone) can produce at a maximum (100% efficiency) only what is supplied to it in the form of mechanical energy IE: 24J/s, or 24W.