280V motor on 230V circuit

[James Sweet]

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.

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.

 

[bz]

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.

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.

[email protected] remove ch100-5 to avoid spam trap

 

[Tzortzakakis Dimitrios]

And so does that 20 gallons of gasoline parked
in front of your house. And that 500 gallons
of diesel fuel in your basment. And that 20,000
or so gallons in the nearby gas station.

Good that terrorists are brain-washed lunatics, and haven't access to
incendiary rounds

Yawn.

--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

--
_____________________________________________________
Knowledge may be power, but communications is the key
[email protected]
[to foil spammers, my address has been double rot-13 encoded]

 

[Tzortzakakis Dimitrios]

In alt.engineering.electrical Tzortzakakis Dimitrios <[email protected]>
wrote:

| ? <[email protected]> ?????? ??? ??????
| |> In alt.engineering.electrical Tzortzakakis Dimitrios
<[email protected]>
|> wrote:
|>
|> | Professional washing machines. One of my very first days 'in the
field'
|> was
|> | to connect some of them. They have a large heating element, you can
|> connect
|> | it single phase, or 3 phase, it just heats up faster (of course) when
|> you
|> | connect it 3 phase. (they have a single phase motor, so it works also
in
|> | pure 230 V).
|>
|> If it has 3 elements rated for 230 volts, with 3 separate connections
that
|> would be to three separate phase for a three phase feed, and all
connected
|> to the one phase for a single phase feed, then it should heat up at the
|> same
|> speed, while drawing three times the current (not accounting for the
|> motor).
|>
|> I don't know why it should heat up faster in three phase, or why you
would
|> say "of course" about it. I would think it would heat up faster if you
|> took
|> it over to London and hooked it up to a 240 volt supply.
|>
| Maybe you connected with single phase just one element? The rest two
| remained unconnected? (3 230 volts elements, connected wye). I'm sure it
| heated up faster, in 3 phase connection.

You were the one who said "it just heats up faster (of course) when you
connect it 3 phase."

I would disagree.

But the fact that you said "(of course)" seems you presume that to be the
general case. Now your most recent comment at least acknowledges that if
not all elements are connected, it won't heat up as fast.

In the simple case, each of 3 elements is individually wired, so you have
a total of 6 leads. When connecting to three phase, one lead of each is
connected to neutral, and each of the other leads is connected to separate
phases. When connecting to single phase, they are all wired in parallel.
Both cases always involve one of the leads from each element connected to
neutral, so those 3 leads can be pre-connected together. So you could
have
just 4 leads. The common neutral lead needs to be rated for all the
current
together for it to be rated properly for single phase.

It should apply the same voltage (230V) to each element, and they should
each
draw the same current. How would you believe this would be slower to
heat?

If the 3 elements were wired _internally_ in star without a neutral lead,
it would still work fine on three phase as long as all elements were equal
impedance. But on single phase, you could only activate 2 of the
elements,
and that would be 2 in series fed with 230 volts. You'd only get 1/6 the
power that way.

Are you assuming the elements would be wired that way? That would clearly
NOT be intended for single phase connection.

The 3 elements could be wired _internally_ in delta. In this case, these
would have to be 400V elements. Connecting 2 leads to 230 volts would
still
give you only 1/6 the power (but more evenly distributed in this case).

So what is the situation that makes _you_ believe that 3 elements
connected
to single phase _will_ draw less power to heat the water than when
connected
to three phase?

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.

 

[Tzortzakakis Dimitrios]

Mine dim slightly for an instant when my 3 ton heat pump kicks in, it's
only noticeable with the few incandescent lights left in the house though.
The LRA on that thing is something like 90A. I think most of the drop must
be in the 50' or so of 2/0 AL wire between the meter base and the
transformer though as they don't seem to dim at all from any of the
neighbors.

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

 

[Daniel Who Wants to Know]

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.

 

[Daniel Who Wants to Know]

Daniel Who Wants to Know wrote:



Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

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.

 

[Daniel Who Wants to Know]

Daniel Who Wants to Know wrote:



Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

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.

 

[PeterD]

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.

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

 

[[email protected]]

| |> 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?

 

[Daniel Who Wants to Know]

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?

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to
ignorance |
| by the abuse department, bellsouth.net is blocked. If you post
to |
| Usenet from these places, find another Usenet provider ASAP.
|
| Phil Howard KA9WGN (email for humans: first name in lower case at
ipal.net) |

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.

 

[bud--]

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.

 

[[email protected]]

| 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?

 

[A. K. SEPUT]

.
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.

"for short period and with limited lenght"

 

[bud--]

"for short period and with limited lenght"

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

 

[Tzortzakakis Dimitrios]

.
I see neither limitation in the US NEC.
.

--

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.