Washing machine 240, 50Hz - 240, 60 Hz?

| The AC side needs a source of AC voltage at the desired frequency. It also | needs to be able to supply reactive. If you are working with a low power
| setup, an oscillator (as you suggest) will do but an AC grid able to accept | what is being transmitted works better when dealing with hVDC systems. | Rather than try to deal with this textually (as diagrams do help) I suggest | that you go to | http://www.hvdc.ca/pdf_misc/dcsum.pdf | as a start. There are more detailed explanations (fraught with equations) of | commutation in various EE texts (both for motor control and for power | systems).
That didn't go into detail in the area I am interested in, which is how you get a good sine wave approximation (to minimize the subsquent L/C filtering) out of solid state switching if you can only do the switch steps during zero crossing. If you do something like pulse width, then you end up switching at other than zero crossing.
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|> That didn't go into detail in the area I am interested in, which is how |> you get a good sine wave approximation (to minimize the subsquent L/C |> filtering) out of solid state switching if you can only do the switch |> steps during zero crossing. If you do something like pulse width, then |> you end up switching at other than zero crossing. | | The receiving system has generation- which is a good sine wave source.
When converting DC (HVDC) to AC (HVAC) which end is the "receiving system". Sorry, I don't know that term.
| Please note that switching is not necessarily at current zeros as in a | single phase system. Switching will occur when an incoming phase takes | over -i.e. current transfers from one set of SCr's to the next- natural | commutation. Note that in such a case , in the rectification region, the | active SCR's will cycle naturally as the voltage of the parallel SCR rises. | In inversion, the same thing is true but the voltage is actually reversed | with respect to the current -reversed power flow. (This is a damned crude | and possibly incorrect way to state it but the key point is that there is | natural commutation from phase to phase. Of course there will be harmonics | and the current in a given AC phase will be roughly a stepped approximation | of a sinusoid- just as in rectification with a 3 phase bridge.
So how do you get the stepped approximation when the incoming voltage is a steady DC? What is the switching rate?
| I really suggest a good text as, on this forum, a good explanation (no | handwaving) is more than I wan't to attempt (and I would have to eradicate | some rust (hey- I am long retired -phase retarded?))before trying in any | case. Follow up leads on HVDC and/ or polyphase (typically 3 to 6 phases or | more) inverters. The only names that I can come up with are old sources, | Kimbark , El Hawari are two authors of power system texts who do touch on | this.
I'm just focusing on a single question. A book or text would be excessive time to just answer a question and I wouldn't pursue it even if you gave me the book.
| It is quite possible that sometime in the future, devices will be developed | that can switch high currents at high voltages opening up the use of pulse | width modulation. Some avenues are being exploited but with how much | success, I don't know. This would solve the DC circuit breaker problem as | well.
Just how high can this switching go in terms of voltage and current now, assuming you can build an array of them in series and/or parallel with syncronized switch as big as desired to get the greatest power level?
Can we do this for say 120 volts at 15 amps?
I'm less interested in the theory of how things work, right now, and more interested in which technology is actually used in real cases, varying from HVDC conversion for power grids all the way down to the gadget that plugs into the cigarette lighter to give you a few watts of 120 volts AC.
I might have an interest in the theory later. I already do understand how things like pulse width modulation and pulse density modulation work. What I want to know is just how far these technologies can go in terms of power levels for real available devices, and how much real inverters might be using them.
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wrote:

------- Receiving end is the AC end in this case. ---------

-------- The DC current will be shared betwen the phases just as in a 3 phase rectifier, The AC phase current will be a series of flat topped alternating pulses with a fundamental frequency dictated by the grid. line currents may have steps if delta or a dual inverter is used. Switching occurs when one phase takes over from another so for a 3 phase there will be 'on" switching every 120 degrees of the fundamental. Look at a 3 phase bridge (single phase won't do) with SCR's. Ignore source inductance and look at the voltage and current waveform assuming a constant current on the DC side. Note that current will switch from one phase to the next when the incoming phase voltage is higher. Look at this for different SCR turn on angles including those beyond 90 degrees where the action changes from rectifier to inverter (current the same but average DC voltage is negative). The reason for referring to books is that they do have the waveforms shown for different conditions.

------------ In the future they may be very useful. I believe that there are gate turn on transistors which show promise at lower levels of current and voltage. However, knife switches work well at low voltages and currents but not at HV levels.
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| The DC current will be shared betwen the phases just as in a 3 phase | rectifier, The AC phase current will be a series of flat topped alternating | pulses with a fundamental frequency dictated by the grid. line currents may | have steps if delta or a dual inverter is used. Switching occurs when one | phase takes over from another so for a 3 phase there will be 'on" switching | every 120 degrees of the fundamental. Look at a 3 phase bridge (single | phase won't do) with SCR's. Ignore source inductance and look at the voltage | and current waveform assuming a constant current on the DC side. Note that | current will switch from one phase to the next when the incoming phase | voltage is higher. Look at this for different SCR turn on angles including | those beyond 90 degrees where the action changes from rectifier to inverter | (current the same but average DC voltage is negative). | The reason for referring to books is that they do have the waveforms shown | for different conditions.
So basically it comes down to the switching speed is no more than the rate of zero crossings. And all of this is because it's such high voltage or current?
| In the future they may be very useful. I believe that there are gate turn on | transistors which show promise at lower levels of current and voltage. | However, knife switches work well at low voltages and currents but not at HV | levels.
If you stack the devices appropriately, and have them well insulated, then you can get some high voltages. Perhaps leakage to air will be the limiting factor. As for switching high current, it seems if the switch is always letting the current go in some direction, it might be doable.
So what is the magic voltage or current below which PWM or PDM is happy?
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wrote:

---------- Yes - or in the case of a 3 phase converter- switching or commutation takes place when the next phase takes over- current through the individual SCR goes to 0 at the same time that it rises in the next one. Chopping doesn't occur. Note that a typical light dimmer will use triacs which are essentially back to back SCR's. You control the turn on time but the turn off time is at the current zero. These are so cheap that there would appear to be little incentive to go to pulse width modulation.
There is a reference on the net possibly from ABB which shows the currents and voltages for rectifier/inverter operation. There is also a reference below which indicates that there have been developments with regard to PWM. in the VSC converters using Gate turn off devices or IGBT (bipolar) devices. These are becoming useful for supplying isolated loads or smaller loads- say less than 200MVA at +/-80KV. SCR bridges are still the sole means at EHV (say 3000MVA at +/- 500KV ) levels. http://www.worldbank.org/html/fpd/em/transmission/technology_abb.pdf

------------ Stacking is already done. A "single" bridge element may have a stack of 4000A SCR's each capable of handling a reverse voltage of 10KV. It is BIG- lots of insulation and high clearances.

--
Outside of the reference above, I have little information. This may help a
bit- look at HVDC light
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| Yes - or in the case of a 3 phase converter- switching or commutation takes | place when the next phase takes over- current through the individual SCR | goes to 0 at the same time that it rises in the next one. Chopping doesn't | occur.
I can see that being reasonable. If phase A is rising in current to the same level and polarity that phase B is falling to, they can be flipped at that point by changing the state of 4 of the 6 gates?
| Note that a typical light dimmer will use triacs which are essentially back | to back SCR's. You control the turn on time but the turn off time is at the | current zero. These are so cheap that there would appear to be little | incentive to go to pulse width modulation.      Based on some waveforms I've seen, some turn on shortly after the zero cross and turn off somewhere mid way through the half cycle. The zero cross seems to be uninvolved. Not all are like that, but many are.
| There is a reference on the net possibly from ABB which shows the currents | and voltages for rectifier/inverter operation. | There is also a reference below which indicates that there have been | developments with regard to PWM. in the VSC converters using Gate turn off | devices or IGBT (bipolar) devices. | These are becoming useful for supplying isolated loads or smaller loads- say | less than 200MVA at +/-80KV. SCR bridges are still the sole means at EHV | (say 3000MVA at +/- 500KV ) levels. | http://www.worldbank.org/html/fpd/em/transmission/technology_abb.pdf
On page 2 see "Force Commutation Converters" ... they _are_ using PWM at higher than power line (net) frequency. No mention of PDM anywhere.
So they do have to be switching things at times other than when the current is at zero or is the same as another phase.
Maybe they can try PDM.
|> | In the future they may be very useful. I believe that there are gate |> turn on |> | transistors which show promise at lower levels of current and voltage. |> | However, knife switches work well at low voltages and currents but not |> at HV |> | levels. |> |> If you stack the devices appropriately, and have them well insulated, |> then you can get some high voltages. Perhaps leakage to air will be |> the limiting factor. As for switching high current, it seems if the |> switch is always letting the current go in some direction, it might |> be doable. | ------------ | Stacking is already done. A "single" bridge element may have a stack of | 4000A SCR's each capable of handling a reverse voltage of 10KV. It is BIG- | lots of insulation and high clearances.
And optical fiber to control?
|> So what is the magic voltage or current below which PWM or PDM is happy? | ---- | Outside of the reference above, I have little information. This may help a | bit- look at HVDC light | http://www.abb.com/industries/us/9AAC751068.aspx which may be the wave of | the future.
I'm interested in the 600 volt and below range. Can something switch a few amps on and off at times the current (and voltage) is not at zero crossing? The idea is to build an inverter that uses high frequency PWM or PDM to chop up the voltage from DC into an LC circuit to filter the high frequency out and produce AC at 50 or 60 Hz (or whatever frequency in that range is programmed in the pulse pattern synthesizer). I also want to do similar as a DC to DC regulator for controlling charge from solar arrays and AC to DC to control and diverter power from wind generators.
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wrote:

--
actually only one or two(possibly) is turned on while another is already
turned on One could use 3 SCR's and 3 diodes if rectification is all that is
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|> | Note that a typical light dimmer will use triacs which are essentially |> back |> | to back SCR's. You control the turn on time but the turn off time is at |> the |> | current zero. These are so cheap that there would appear to be little |> | incentive to go to pulse width modulation. |> |> Based on some waveforms I've seen, some turn on shortly after the zero |> cross |> and turn off somewhere mid way through the half cycle. The zero cross |> seems |> to be uninvolved. Not all are like that, but many are. | -- | If that is the case- I don't know what you are looking at. Which zero | crossing - voltage or current ? | SCR's or Triacs that I have known don't do that. Are you sure something is | not reversed or out of whack in the scope?\
For resistive lights, the zero-crossing is pretty much the same. But as I am referring to waveforms that rise up from the zero-crossing and are then just suddenly turned off, there is no ambiguity unless this involves radically low power factors.
These are waveforms I have seen published. I don't know what is being tested. But the point is that _something_ actually _can_ shut off at least a few amps of current. Whether it is a Triac, SCR, Thyristor, or what, I either didn't see, didn't care, or didn't remember at the time. I was only concerned with the harmonics of the waveform, not in how to achieve the waveform, back then.
My concern today is finding devices to turn voltage and current on and off at points specifically controlled. I'm not dealing with the power levels of transmission grid AC/DC or 50/60 converstion. What I do want to look at is DC regulators and DC to AC inverters in power levels up to 10kw or 20kw. But that's NOT per individual component. A design could parallel many components if need be. Ideally, such a device would have fast switching that would allow using pulse density modulation and be easier to filter. But pulse width modulation is certainly usable.
|> And optical fiber to control? | ----- | Yes that is used.
I don't know if I will need an optical control for turn on/off operations. The DC voltage levels could be from 48 to 600 volts open-circuit.
|> I'm interested in the 600 volt and below range. Can something switch a |> few |> amps on and off at times the current (and voltage) is not at zero |> crossing? |> The idea is to build an inverter that uses high frequency PWM or PDM to |> chop up the voltage from DC into an LC circuit to filter the high |> frequency |> out and produce AC at 50 or 60 Hz (or whatever frequency in that range is |> programmed in the pulse pattern synthesizer). I also want to do similar |> as a DC to DC regulator for controlling charge from solar arrays and AC to |> DC to control and diverter power from wind generators. | ------ | OK- this is low power/voltage stuff and is doable. It appears from the | reference that I gave that there have been advances in such switching. It | very much depends on the circuit inductance. Chopping involves high Ldi/dt | voltages which can cause problems. Obviously inverters do exist at this | level and are available on the market.
I don't know what is obvious. A number of inverters do exist on the market but so far not a single one of them reveals what technological method they use to convert DC to AC. Given the efficiency figures of _most_ of them, I'll confidently speculate they are not using class A analog amplifiers. For a few, I could not rule out a class B or maybe even a class C. I don't know if they are doing digital or analog.
One idea I want to explore in an inverter design based on pulse density modulation is to use pulse scattering among the individual components doing the pulse gating. Instead of having every component all gate on or off at exactly the same time, it would be rotated. So if the density level is at say 12.5% and there are 8 components in parallel, each one could be on for 12.5% of the time and all at different times. When the density is at 75% (voltage peaks under load), there would be overlap of on time, but the off times would now be rotated with some overlap.
12.5% on 25% pdm 25% pwm 50% pdm 50% pwm 50% hybrid gate0 10000000 10001000 11000000 10101010 11110000 11001100 gate1 01000000 01000100 01100000 01010101 01111000 01100110 gate2 00100000 00100010 00110000 10101010 00111100 00110011 gate3 00010000 00010001 00011000 01010101 00011110 10011001 gate4 00001000 10001000 00001100 10101010 00001111 11001100 gate5 00000100 01000100 00000110 01010101 10000111 01100110 gate6 00000010 00100010 00000011 10101010 11000011 00110011 gate7 00000001 00010001 10000001 01010101 11100001 10011001
This is just multiple gates for an individual phase. Multiple phases would each be under a different density percentage according to that phase's current point in the cycle, and any load imbalance.
Most other percentages would be more complicated. There would be more pulse intervals per cycle, variable cycle times, and a lot more gates. Control circuitry would be designed to ensure a balance of on-times among all the gates, possibly influenced by sensed temperature. The input LC circuit would smooth out the incoming DC current, and the output LC circuit would be there to smooth the pulses to a relatively clean sine wave and supply at least some reactive current. The control circuit would adjust the desnity/width of pulses to maintain the appropriate voltage in the output tank based on the power demand. It might well be measuring both voltage and current and making adjustments accordingly.
Other projects that would use some of this would be charging regulators for charging batteries from photovoltaic sources, and diverters for wind generators to manage the alternator loading under varying usage loading and wind speeds. It might also manage the exciter power for alternators not using permanent magnets.
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wrote in message

--------- With a conventional SCR or a Triac, I can see the waveforms that you describe- if the scope was across the dimmer. In that case one would expect the voltage to rise to full line voltage and follow that until the device is gated on(assuming SCR's or triacs which are cheap in the size involved) - after that the voltage across the device would be the normal forward drop of a diode. What would be of interest is the load voltage and current. A inductive pf near 1 (not low) would cause a slight delay in the current zero and this accounts for the "shortly after" that you mentioned.
I too doubt if there is a low power factor- most lamp dimmers can't cope with loads such as motors and a "dimmer" meant to handle a small motor is quite a bit more expensive than those intended for incandescent lamps.
There is also the possibility that the device is a gate turn off device. http://www.machinedesign.com/BDE/Electrical/bdeee6/bdeee6_20.html
I am not familiar with these devices ( retired about 12 years ago and wasn't involved with advances in power electronics ) but it seems that for PWM devices, they are the cat's meow. For simple lamp dimmers- probably not. ------------

--------- Look to the GTO's -there are many manufacturers in this area and seem to cover well beyond your needs. >

-------- Looks interesting and doable if what I see is now available in GTO's etc.
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| With a conventional SCR or a Triac, | I can see the waveforms that you describe- if the scope was across the | dimmer. In that case one would expect the voltage to rise to full line | voltage and follow that until the device is gated on(assuming SCR's or | triacs which are cheap in the size involved) - after that the voltage | across the device would be the normal forward drop of a diode. What would be | of interest is the load voltage and current. A inductive pf near 1 (not low) | would cause a slight delay in the current zero and this accounts for the | "shortly after" that you mentioned. | | I too doubt if there is a low power factor- most lamp dimmers can't cope | with loads such as motors and a "dimmer" meant to handle a small motor is | quite a bit more expensive than those intended for incandescent lamps. | | There is also the possibility that the device is a gate turn off device. | http://www.machinedesign.com/BDE/Electrical/bdeee6/bdeee6_20.html | | I am not familiar with these devices ( retired about 12 years ago and | wasn't involved with advances in power electronics ) but it seems that for | PWM devices, they are the cat's meow. For simple lamp dimmers- probably not.
[...]
| --------- | Look to the GTO's -there are many manufacturers in this area and seem to | cover well beyond your needs. >
It sounds like a gate-turn-off device might be what I want.
[...] | Looks interesting and doable if what I see is now available in GTO's etc.
I'll need to find out what voltage between line and gate, and what current it can handle, principly for gating off. My bet is capacitors will likely need to be very close on both sides to minimize the voltage rise as the gate shuts off.
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number of

motor was

connections to

I read on some obscure Web site that the reason for 25 Hz was basically that the Niagara Falls turbines had been ordered before they'd quite made up their mind how to get the power out (AC? DC? Compressed air?) and they turned out to be the wrong RPM to make an alternator at 30 Hz. Westinghouse wanted 30 Hz for motors and 60 Hz for lighting, but settled on 25 Hz at Niagara which then spread over the immediate area. By the 1950's Ontario had to go around and replace or modify a bunch of appliances when they decided to go to 60 Hz.

including
equipment-
Brits had

still find

Until just after WWII, parts of California were 50 Hz. And Japan to this day is split in half, part 50 and part 60 Hz. The Itaipu project has some 50 Hz generators and some 60 Hz. And Ontario still has a couple of 25 Hz powerhouses on the Niagara, in case a frequency converter fails some day....
Bill
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I thought the conversion happened during WWII, driven by connection of Hoover dam to the LA area. Mexico City was post war.

I'm curious about the story behind that... Not just the anactodtal, but the full blown story.

The treaty behind the dam gives 1/2 of the power to Peru and 1/2 to Brazil. The Peru generators are 60Hz and the Brazilian generators are 50Hz. The most amusing part is that more than half of the 60Hz output is converted to DC and sent to Brazil to be converted to 50Hz since Itaipu produces more power than Peru needs.
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Hey, I never said it was bad... just pointing out what would be different.
Of course we could just go to DC for most transmission and the frequency wouldn't matter.
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|
| |> | |> |> There are many aspects of the US/North American system I don't like. |> |> The 60 Hz is about the only thing I do like about it. I'd rather go |> |> on up to 72 Hz. |> |> |> | |> | hmmm... 4320 RPM and 2160 RPM generators. More power in the same size |> | generator, but the turbines would change, some for the better, some for |> the |> | worse. |> | |> | X sub L of the power lines increased by 20%. Charging currents increase |> by |> | 20%. |> |> Oh, well, then let's go to 36 Hz. |> | | Hey, I never said it was bad... just pointing out what would be different. | | Of course we could just go to DC for most transmission and the frequency | wouldn't matter.
For long distance transmission, that is already happening to some extent now. Given the effective transmission distances have increased based on the way power is traded around, and the heavy reliance on the grid that was originally intended for backup purposes, DC might be a better choice for even more.
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AC Transmission = One less conductor and its associated set of insulators, more efficiency, minimal reactance, no AC induced voltage to fences, telephone wires, other adjacent transmission circuits, no ac vibration stress on conductors.
Downsides - More complex and expensive substations - Circuit breakers are harder to break arcs under load.
My question - Do they do live line work on DC Transmission? (i.e. clamping an insulated lift truck platform or bonding a worker from a helicopter to an energized line). I know AC induction is a problem for linemen, but what about steady state DC electric fields?
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The bonding or clamping of an insulated platform is not to done to deal with inductive effects but the electrostatic effects. The same conditions as for AC will be there for line workers. The same techniques will be used for protection, including bonding and mesh outerwear to make the body an equipotential. Line workers connected to the live line are not concerned about induction but about distortion of the electric field due to their presence. Whether actual line work is done live- I guess that depends on the utility, and the location and the economics of doing so.
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| I have a European LG washing machine model # WD-90150(5)FB. It was designed | for 240V, 50 Hz. | | Does anyone know what parts need to be changed to make it run on 240V, 60 Hz | and where could I get a wiring diagram? | | I already checked with the US: snipped-for-privacy@lge.com and it was a complete | waste of time. They seem to know nothing.
The people that really know anything, engineers, are kept isolated in special places called cubicles, incommunicado with the rest of the world.
About a year ago I was talking to a guy who sells "220 volt" appliances in the USA that would normally be available for 120 volts. I was asking him about how things like clothes dryers, which need a very specific tumbling speed, handled the different between 50 Hz and 60 Hz, since a few countries (e.g. Brazil) do have 240 volts at 60 Hz. He said that a lot of models could be easily converted. The motor and drum each had two belt positions, one smaller and one larger. In 50 Hz countries the belt would be on the larger rim of the motor and the smaller rim of the drum. In 60 Hz countries, that would be reversed with the same belt size. A washing machine would involve more forces, so I don't know if they have belts as such, but maybe a chain?
What I am looking for is a clothes dryer that everything within uses only 240 volts and nothing at all uses 120 volts. This would allow it to work without a neutral. I was thinking maybe a European/Asian model might be what I am looking for.
For a washing machine, I'm looking for similar, but also with built-in water heating so that it can run directly from only cold water. I would expect this to require more power, possibly more than the dryer. I had seen some that stated they had heaters, but now I think they are just supplementary heaters that allow using hot water tanks that operate at lower temperatures (below 50C).
I'm also looking for 240 volt versions of in-sink garbage disposal/grinder. As their motors are usually over 1/4 HP, NEC 210.6(a)(2) would not be an issue to use 240 volts. That rule specifies that no more than 120 volts may be used for cord-and-plug connection loads unless the load exceeds 1440 VA or is 1/4 HP or more.
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snipped-for-privacy@ipal.net wrote:

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george snipped-for-privacy@yahoo.com wrote:

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