A diode in series with a brushed universal motor?

Not concerned about safety for this discussion.

What will happen if you put a diode in series with a universal brushed motor? Of course talking about a diode that can handle standard USA 120 V

60 Hz household power. Just putting a diode on one of the wires coming from the outlet, to rectify the current. Would a capacitor after the diode be useful? What sort of capacitor would be required for a 14 amp motor?

Thanks.

Reply to
John Doe
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I think you'd find very different characteristics.

For a start the field acts as an inductor and so the voltage-current waveform would be very different.

There would be less transformer action between segments and less loss; more likely for motor to overspeed.

I would have thought a bridge rectifier would be a better bet, and cheaper than a capacitor.

Less current limiting at low speeds through less motor impedance at DC.

BICBW

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk
Reply to
Mike Perkins

** The motor slows down and the max available torque is down a bit too.

Most SCR drill speed controllers are half wave at full setting, just like a diode.

** It defeats the purpose of the diode and increases the motor's rpms.

One diode and one cap makes DC supply from the mains of 170V.

... Phil

Reply to
Phil Allison

It will vibrate a lot and the speed will be less stable if you give it half-wave AC from a single diode. At 14 amps, you'll make a mess of your line power too. Nearby devices with line frequency transformers may run hot from asymmetry producing DC current.

Do NOT use a rectifier and capacitor on a 14 amp motor. A bridged rectifier alone is not terrible (a bit more power) but adding a capacitor will cause an extremely bad power factor. Your combination of rectifier and capacitor will essentially smash in the ends off the AC waveform. You'll get spikes of very high current at very high voltage for a relatively small output wattage. That's fine for 1 Watt wall warts but you'll cook your AC wiring doing that for a 1.7 KW motor.

--
I will not see posts from astraweb, theremailer, dizum, or google 
because they host Usenet flooders.
Reply to
Kevin McMurtrie

** LOL - what utter CRAP !!

and the speed will be less stable if you give it

** No it won't.

** FFS - it's only for intermittent use.
** FFS - you mean *transformers* on the same loop may draw more primary current because the AC is slightly assymetrical - ie has a small DC offset.

Another false alarm.

** Huh ?? What bollocks.

Shame about every full wave rectified DC supply already on the planet.

Was your mother called "Henny Penny" ??

** ROTFLMAO !!!

** Stop it, please, that is tooooo funny.

Take a bucket of sanity pills and have a good lie down.

You stupid, know nothing prick.

... Phil

Reply to
Phil Allison

It will run slower. Lots of small domestic appliances do just this for the slow speed option.

piglet

Reply to
piglet

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