rotary inverters

turns

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Finally found one vendor: Redi-Line

Googling around, I got the impression rotary inverters were more common in the 60's or so.

Mike

Whoa... they run about $600 or so for the small one (500W).

Guess it might be worthwhile to try and make one from scratch after all...

Mike

More fundamentally, I've considered rounding up an old M-G (as in gasoline motor) set as the ultimate in UPS ;-)

...Jim Thompson

This was obviously written long ago - with modern electronics you can control the frequency just fine.

I haven't worked with rotary inverters, but I have worked with rotary converters; a 60Hz motor driving a gear driving a 50 Hz. generator. It was 12 feet high and 20 feet long, and was the lowest-cost way to get a *lot* of true simewave 50 Hz. power. I suspect that the economics are the same with rotary onverters.

By a gasoline generator and replace the engine with an approriate DC motor and gearbox. You can make a go-cart out of the engine. :)

Military surplus stores maybe ? They used to use these things a lot.

Graham

Hmmm.......

A friend approached me about designing sinewave inverters to run off bus / coach batteries to drive video entertainment systems about 20 yrs ago. He couldn't come up with a spec so I told him to get lost.

Surely someone must have done this economically by now ?

If you mentioned exactly what equipment you want to use from what kind of source - at what power level - we might be able to help you better.

Graham

UPS + MG set

In the past, Arizona has been noted for multi-hour outages.

At this "new" house I hadn't had a single outage for 11 years UNTIL last week when we were down for an hour.

SInce I often have multi-hour PSpice simulations in progress a typical UPS can't hold up that long, thus the MG set idea.

...Jim Thompson

As I recall, rotary inverters/converters were common in larger telephone exchanges with trunk carrier equipment and valve operated repeaters which required voltages higher than the normal -48V back in the 60's. They were more commonly referred as no-break plant. They ran permanently from a separate battery which was charged while ever mains supply was available. The no break alternator output voltage and frequency was synched to the mains supply and when the mains failed the no-break plant instantly supplied mains voltage until a diesel motor generator was up and running. When the diesel plant had its alternator output synched to that of the no break plant then the no break plant was disconnected. This way there was no interruption to the operation of the exchange trunk carrier equipment.

On Thu, 24 Feb 2005 19:03:40 -0700, Jim Thompson wroth:

The "U" in UPS stands for uninterruptable. Do you plan to have the MG set running continually? Or have you come up with a way to get the motor started and up to speed in a fraction of a second?

Otherwise it would only be the ultimate in SPS or Standby Power Supply.

Jim "The other one" Meyer

It's called a dynamotor. Some of them on E-bay. I used to see them at ham-fests all the time. getting kind of rare. I think there were a lot of them from military surplus places.

For sine wave inverters that kind of look like dynamotors, go to

boB

If the goal is DC to AC or teh other way around a single armature can be used, with brushes on one side (the DC side) and slip rings on teh otehr side (the AC side).

This saves a lot of iron I think.

Thomas

I'll have to see if it's playing here in Phoenix.

PBS has gone seriously down hill, playing mostly politically-correct BS, so I let my support membership lapse after more than thirty years as a "gold" member.

I don't think I've turned on that channel at all in the past year.

Switching is downright trivial with a UPS...

Lose AC for more than 15 minutes, drop AC connection to UPS, start MG set, connect MG set to UPS. Synchronization isn't an issue at all.

Biggest problem would possibly be gasoline degradation while it sits. Might be better to go with a natural gas unit, or, in my case of an all-electric utility situation, a propane unit.

...Jim Thompson

Seems that "This Old House" is now re-playing only on the DIY network.

Is that where you saw it?

...Jim Thompson

Do you watch "This Old House" at all? The barn they're renovating now has a nice gas-powered generator. Perhaps something like that would work, combined with a small backup battery array and inverter. Tricky part would be load-switching from battery/inverter to generator. Prolly easiest to buy a premade unit for the job?

I see it here (Oregon) new (they say) each week. I've also seen episodes (don't know if re-run) on the DIY network.

They also run the "Ask this Old House", a separate home repair program with the same people just before the other program on Saturday afternoons here.

Robert

Around here if its more than a few seconds its usually several hours because its a blown fuse in an outdated 7200 volt distribution system. A 60 amp fuse feeding about 40 homes. It was built for 60 amp service per home 41 years ago. Most homes now have 200 amp service, the rest are 150 amp. Almost every home has an electric stove and central air. A few have electric heat, as well. The numbers don't add up on hot days, or the few really cold days when a heat pump won't keep up and the heat strips kick in.

be

otehr

Yeah, I built one of these during my college days, after our physics professor mentioned slip rings. Had a 1.5V DC motor pull a pulley that drove the slip rings (made from washers); my "inverter" generated a type of square wave. Wasn't very efficient; there was a short circuit for a few milliseconds when the brushes touched both the positive and negative inputs.

Was loads of fun putting in 6VDC (four C-batteries) into it, then wiring the output to a step-up transformer that my dad had kept hidden from me all those years... added a bridge rectifier and capacitor to the output... it even drove a 120VAC night light.

Mike

Oh sorry I meant "Ask This Old House." It appears on PBS here in Ohio new on Wednesday nights, and is repeated on Saturday afternoons. The generator is a natural-gas type.