280V motor on 230V circuit

Do you actually use a setup like that? I'd think that for any sort of current, the filament windings would be melting down even though they are made of fat wire. For example, at 300 VA of output, you're looking at ~100 A in the filament winding.

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Connecting the HV windings together would probably work a lot better. Would want to knock out the magnetic shunts too, that can be tricky but I've done it on several without damaging the windings.

James Sweet wrote in news:HT%%j.670$BV.298 @trndny05:

I wanted some heavy copper wire to wind a coil with so I tore xxxx started to tear up an old microwave transformer. Found out that pretty copper wire was aluminum with a copper colored layer on top of it. :(

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I have no idea, we didn't even open up the washing machines as they were under guarantee. I know that the landlady's electrician connected the wms single phase, and I connected (in the distr.box) all 3 phases. I suppose it has 3 elements connected wye, and single phase is 1 element, plus motor and automation.

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? "James Sweet" ?????? ??? ?????? news:HKnVj.128$6D1.49@trndny02...

That's because you have no bloody wind-turbines on your grid. We have here, and I had to include them in my thesis, and these things seriously harm the voltage quality in interconnected grids. In stand-alone residence installations, they work ok, probably with photovoltaics, but here they are a disaster, in whole Crete all the lights flicker every evening when the bloody wing stalls them and they convert momentarily from generating to motors. I prefer old-fashioned fossil-fuel fired power plants, after all smoking chimneys is a token of peace:-)

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You need to move your politicians closer to the turbines, to maintain a higher efficiency. This detail os often overlooked in this type of installation. ;-)

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Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the cord is a 14-3 AWG with one conductor being ground, yes it is single phase. :-)

Each mag has its own waveguide with a rotating antenna at the end that extends into the oven cavity. 2 of the waveguides are at the top of the cavity firing down and the third is at the bottom firing up. The HV transformer primaries are wired so that the top 2 mags fire on the positive alternation of the AC sine wave and the bottom mag fires on the negative alternation. The top 2 antennas are driven by a single timer motor with large plastic gears (complete with timing marks) so that they both are pointing the same direction at all times as they rotate. The HV transformers have tapped primaries so that the oven can operate on either

208 or 230 volts with no change in output power. Also there is a small 208-230 volt boost autotransformer that boosts the voltage for the cavity lamp, cooling blower, and antenna motors when the oven is plugged in to 208. When the microwave is first plugged in it sits for about 30 seconds to (I assume) to sense the supplied voltage and frequency so that it uses the correct taps on the 4 transformers. Oh yeah when the oven is set for less than 100% power the HV transformers are cycled on and off by 3 triacs (1 each) with arc snubbers across them and there is a relay that cuts the power to the triac/transformer circuits when the oven is off. Each mag has 2 thermal cutouts, 3 cut off the power to the respective transformer primary and the other 3 are wired in series and are connected to the logic board which makes the vacuum fluorescent display show HOT and also causes the oven to refuse to operate. There is also a thermal fuse in the oven cavity air discharge duct.

I think I have provided WAY more info than anybody wanted or needed.

In my other post I forgot to mention that Sam already has most of what I wrote posted on his site somewhere as I sent him the details awhile back.

Perhaps more info, but intersting info, and appreciated.

|> | Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and |> has 3 |> | HV magnetrons along with 3 each of the other necessary items (cap, |> diode, |> | etc.). It even has a current transformer that tells the control board |> via |> | current draw when the magnetrons are warmed up so that the timer doesn't |> | start counting down until it is actually cooking. It has a standard |> NEMA |> | 6-20 plug on it now and will pop a bag of popcorn in roughly 75 seconds |> | without scorching it. I can tell you it sure beats the hell out of |> regular |> | microwave ovens for most things. The only thing I still use the regular |> one |> | for are items that involve liquids as the Amana tends to make them |> either |> | boil over or boils out all of the water before the food is cooked. |>

|> Will it operate on single phase power, like I have in my home? |>

| | Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the | cord is a 14-3 AWG with one conductor being ground, yes it is single phase.

Don't be so quick to jump to conclusions. The NEMA 6-XX series gets used for both the 208 volt 120 degree and the 240 volt 180 degree 2-wire connections. Some devices work on one and not the other. You CAN derive three phase from one and not the other. A motor could be wired to use that angular difference (with the neutral) to achieve a motor starting direction instead of having a capacitor to change the angle on a shaded pole.

Also, if the supply is 208 volts then the maximum power available is 4157 watts (3326 under the 80% rule), whereas with 240 volts it is 4800 (3840 under 80%).

240 volts is a 15.47% increase over 208 volts. 277 volts is a 15.47% increase over 240 volts. Can either of those be substituted for 240 volts easily?

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In this specific application the third prong is used only as a chassis ground connection as everything including the light bulb is 230V. Also I am no expert here but I think intermittent loads can exceed the 80% rule hence the 14 gauge cord which would normally only be good for 15 amps but is protected by a 20 amp fuse inside the oven and a 20 amp double pole circuit breaker in the service panel. The NM-B (Romex) I used is 12-3 with ground and has the white neutral conductor simply capped but not connected at either end.

Daniel Who Wants to Know wrote: >

. The US NEC allows about any cord of 2 conductors (not including ground) to be used at 18A. Most (all?) cords with type starting H (hard use) can be used at 20A.

The 80% rule is for continuous loads - over 3 hours.

--
bud--

In alt.engineering.electrical bud-- wrote: | Daniel Who Wants to Know wrote: | >

|> Also I am |> no expert here but I think intermittent loads can exceed the 80% rule hence |> the 14 gauge cord which would normally only be good for 15 amps but is |> protected by a 20 amp fuse inside the oven and a 20 amp double pole circuit |> breaker in the service panel. | . | The US NEC allows about any cord of 2 conductors (not including ground) | to be used at 18A. Most (all?) cords with type starting H (hard use) can | be used at 20A. | | The 80% rule is for continuous loads - over 3 hours.

Like a computer?

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"for short period and with limited lenght"

. I see neither limitation in the US NEC. .

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Correct. #14 is the same as Europe's 4 mm^2-which we usually use here in Greece for the regular, 4 kW hot water heaters. It's rated for 20 A continuous duty when in a conduit with 1 live conductor (IIRC), we don't have extensions in that gauge. We usually protect it with an 20 A circuit breaker (single pole, aka automatic fuse) and a double pole circuit breaker (aka switch) which is not automatic, just to turn on off the water heater. There are 3kW heating elements, too, for older installations, which are quite incapable of sustaining a 4kW load.

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