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280V motor on 230V circuit

Discussion in 'Electronic Repair' started by Deodiaus, Apr 26, 2008.

  1. James Sweet

    James Sweet Guest


    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.
     
  2. bz

    bz Guest

    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. :(




    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  3. Good that terrorists are brain-washed lunatics, and haven't access to
    incendiary rounds:)



    --
    Tzortzakakis Dimitrios
    major in electrical engineering
    mechanized infantry reservist
    hordad AT otenet DOT gr
     
  4. 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.
     
  5. 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:)
     
  6. 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.
    :)
     
  7. 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.
     
  8. 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.
     
  9. PeterD

    PeterD Guest

    Perhaps more info, but intersting info, and appreciated. <g>
     
  10. Guest

    | |> In alt.engineering.electrical Daniel Who Wants to Know
    |>
    |> | 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?
     
  11. 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.
     
  12. bud--

    bud-- Guest

    ..
    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.
     
  13. Guest

    | 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?
     
  14. A. K. SEPUT

    A. K. SEPUT Guest

    "for short period and with limited lenght"
     
  15. bud--

    bud-- Guest

    ..
    I see neither limitation in the US NEC.
    ..
     
  16. 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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