Sciencemadness Discussion Board

Convert US power cord to european.

batsman - 25-8-2013 at 06:10

Hey, i got a hotplate from ebay, i thought that i just needed to get one of those adapters, but it turns out its not possible.

What can i do?

bfesser - 25-8-2013 at 06:33

Provide specifics or no one can help you.

Endimion17 - 25-8-2013 at 09:30

Converting a socket is a piece of cake. You can get such converters for a dollar on eBay.
Converting 120 V @ 60 Hz to 220 V @50 Hz requires a transformer and therefore more money.

IrC - 25-8-2013 at 12:13

Quote: Originally posted by Endimion17  
Converting 120 V @ 60 Hz to 220 V @50 Hz requires a transformer and therefore more money.


No transformer will convert 110 Vac@60 Hz to anything at 50 Hz. The 60 Hz power would have to be converted to DC to run a chopper circuit which is running at 50 Hz. Inverter is the term. However at high current it would require a very high power model. A motor-generator (alternator) would be more efficient and waste less energy as heat. Would need to run very slow however to output 50 Hz, so make the alternator half really large in diameter and gear it down as the motor side would run at a line synched frequency. Besides it sounds more like you are asking how to operate a US designed hotplate on EU power. Running a hotplate on a solid state inverter would not be a good idea.

The hotplate is not going to worry about a 10 cycle difference in frequency as it is merely a resistive heating element. I do not know how outlets are wired over there in the EU but I imagine it is 220 volts from line 1 to line 2. If as here the pole transformer has a center tapped neutral then one would think a connection from either line to neutral would be 110 volts. So center pin (earth) to either line would run the hotplate assuming the outlet can handle the current safely. Unsure why in the EU one would buy a hotplate on fleabay designed for US use. However again assuming the current at 110 volts does not exceed safe wiring practice there you could always buy another identical hotplate, wire them in series and cook two things at the same time.

Looking at the title "Convert US power cord to european" I am assuming it is a hotplate designed to plug into an outlet here, 117 Vac@60 Hz, and He desires to plug it into a 220 Vac @50 Hz outlet over there.

In any case always remember this. No hotplate is worth burning down your house (or anyone Else's for that matter). This is in no way a put down or insult: by asking the question you demonstrate being unfamiliar with power service wiring for either your grid or the hotplate. Therefore even less familiar with safety issues. My advice: pay an electrician the bill will be far lower than the possible costs should things go wrong. You could also get a 220 to 110 step down transformer but it would need to be a 2KVA model to give 50 percent de-rating.

Needed as hotplates draw several amperes and you do not want enameled turns to overheat and short together. Remember being a hotplate one must assume it is going to be on for quite a while at a time.

@AndersHoveland
"I do not think the frequency is really that important, especially such a small difference."

Exactly. What I was saying in this very post just above: "The hotplate is not going to worry about a 10 cycle difference in frequency as it is merely a resistive heating element." It is useful to read all of a post before posting the same thing over again while quoting from the post obviously not read to begin with.

However other things may care a great deal what the frequency, not important for the OP's question but I add it for clarity.

Anyway hopefully I confused no one by answering AH's post below in this location, just saving adding another post.


[Edited on 8-26-2013 by IrC]

AndersHoveland - 25-8-2013 at 12:31

You might be able to get your hot plate rated for higher voltage to run on lower voltage. Certainly there would be no harm in trying. Likely the power would be only about a fourth as much, but you might be able to boil water if you set in on the highest setting. Even if it cannot boil water, it might still have some use distilling alcohol, especially if you have a vacuum pump.

I think European voltage is typically 230V, and American voltage is typically 120V.

A hot plate is a rather simple circuit, for all practically purposes it is essentially just a resistor-like load. It could be able to take somewhat of a range of voltages, assuming it does not overload (but if you wanted to try running an American hotplate on European voltage, I would strongly recommend putting it on the lowest setting, and measuring the heat to make sure it is not any greater than what it should be).
Quote: Originally posted by IrC  
No transformer will convert 110 Vac@60 Hz to anything at 50 Hz.

I do not think the frequency is really that important, especially such a small difference.

phlogiston - 25-8-2013 at 16:40

Quote:
Looking at the title "Convert US power cord to european" I am assuming it is a hotplate designed to plug into an outlet here, 117 Vac@60 Hz, and He desires to plug it into a 220 Vac @50 Hz outlet over there.

Quote:
You might be able to get your hot plate rated for higher voltage to run on lower voltage.


There is clearly some confusion as to what you are trying to do, so you should clarify it a bit more.

I am assuming you are want to power a hotplate designed for US 120V from a european 230V socket.

As AndersHoveland says, they often are essentially just a big resistor, and then the frequency, waveshape etc do not matter. You do need to limit the power to the thing to prevent it from overheating. So, a cheap solution might be to run it via a dimmer circuit set at approximately 50%. These typically work by PWM. Make sure it is rated for the power you need.

woelen - 25-8-2013 at 23:23

@IrC: Over here we do not have a configuration as you suggest. In a single-phase installation we have two identical poles, one is firmly connected to earth and the other is at 230 V AC. Plugs can be rotated 180 degrees and fit again. We have a separate earth pole as well, which can easily be touched, while the other two poles are deep inside the socket. Because of the rotation-possibility we need that third pole, otherwise two poles would be enough.

So, there is no center-tap with two 115 V AC poles which are each other's inverse voltage. We need a real transformer to bring down the voltage to 110 V or so. I expect no problem at all for the hot plate if it operates at 50 Hz instead of 60 Hz, so I would buy a sinple 1 : 2 transformer and put that between the AC-outlet and the hot plate. The transformer, however, needs to be a fairly large one, because it should be capable of supplying at least several hundreds of Watts (look at the max. power rating of the hot plate).

Use of a dimmer circuit _might_ be possible, but I am reluctant to suggest the use of such a thing. A dimmer circuit only alters the shape of the wave form (it chops off part of the sine wave), but it does not change the peak voltage. If the dimmer is set to 50% (time based), then you still have twice the power of normal full power operation at 110 V.

IrC - 26-8-2013 at 00:16

So you have a single ended grid. Forces you to do everything at 220. That sucks. I agree the lamp dimmer idea is not a good one (or not so bright). In my post above I stated likely a 2 KVA step down transformer is needed for safe 50 % de-rating since the hot plate will be on a long time, and typically on high they pull 8 to 12 amps. Or around 1 kilowatt constantly. Problem is a 2KVA 220 to 110 transformer is going to be very expensive. Makes no sense to me. Buy two and run them in series heating two things at once is far cheaper but stupid. Obviously the sane route is to toss it and buy a 220 volt model. Far cheaper in the long run. Occurs I should ask: look at a pole pig outside. Is there two or three bushings on the side? (the terminals which run into the weatherhead on your home). If three are only two connected? On top is there two taller bushings going to overhead wires or only one? If two, is there two or three wires in the high tension run between poles?

I have noticed few actually read all of a post before commenting, usually the first line that's it. Is that true or is it just my imagination?


[Edited on 8-26-2013 by IrC]

woelen - 26-8-2013 at 11:01

We do not have wires in the air, all wiring is underground. Only the main transport net is above ground (110 kV, 150 kV, 220 kV, and 380 kV). This is transformed down to nearly 11 kV in most places and this 11 kV then goes to suburbs where it is transformed down to nearly 400 V AC.

Actually, we have three phases and a single common neutral (earth). Each of these phases is at 230 V AC, relative to earth (the common neutral), with a phase shift of 120 degrees between each of the phases. So, in a fully connected 3-phase socket we have four poles, three for each phase and one for grounding. Between two phases there is nearly 400 V AC (230 * sqrt(3)). For many houses, it is decided to only use one of the three phases plus the neutral, but as a end-user you can also have all three phases for equipment, which needs higher power.

IrC - 26-8-2013 at 11:59

You have no idea how much I envy you then even if it does force you to buying big transformers to acquire 117 VAC. Underground wiring means no crap on my receiving gear (at least far less). Plus the added bonus of serious 3 phase power which in my 2 story tall Tesla coil days back in the late 80's would have been great. I had to rent an industrial location for my big coils as home number 2 service was very lacking for the mad scientist in me.

Wye or Delta? I'm assuming Delta or is the 4th conductor just a safety neutral?


papaya - 26-8-2013 at 12:14

If I understand it right you want to run stuff designed for 120V at 220V ? I can suggest you to place a powerful diode(it can be not very large) in series with your plate - that must give about the half of power of what you would get from just directly powering it at 220 (correct please if I'm wrong).

woelen - 26-8-2013 at 12:38

@papaya: That does not sound like a safe thing to do. The hot plate still receives peak voltages of 300 V and still has two times the power of a full load at 110 V. The insulation in the heater may break down at such high peak values (the heater is designed for 110 V). I would not feel comfortable with such a heater operated at double peak voltage and double power.

@IrC: As far as I know, the transformation from 11 kV to 400 V uses a delta configuration at the high voltage side and a delta configuration at the domestic voltage side, but I am not 100% sure of this. Sometimes there are other configurations. But every house has a hard ground pole and the three phases all have 230 V relative to ground and 400 V between phases (120 degrees phase shift, which implies a factor of sqrt(3)). This property almost certainly excludes a wye configuration at the domestic voltage side (otherwise the neutral point could fluctuate in case of asymmetric load on the different phases, which is not the case).



[Edited on 26-8-13 by woelen]

papaya - 26-8-2013 at 13:49

How you managed to calculate double power woelen ? Diode strips the "half" of the wave, so ideally power is halved, even if peak voltage remains high. Taking into account how inert thing is the heating element in regards to thermal response speed - you can think of it as an integrating element, but I agree in general that the idea is risky - be prepared to burn it (if diode fails for example).

IrC - 26-8-2013 at 20:24

Another advantage you have woelen is minor CME's from the sun could easily reduce us to batteries whereas your grid is so well protected by the shielding effect of the earth. Plus your view is so great. We have to see all that crap hanging around everywhere we look. I have always despised wires strung all over the place. Hate to count how many scenic pics I have had trouble with due to power lines. And If I put up an antenna I need to worry about disasters only feet away waiting for the antenna to land against. Really irritates me our grid is so decrepit and ugly. I could also add likely your power does not go out in every storm. They should have started over 40 years ago replacing our overhead grid with underground power.

On the diode question the PIV should be at least twice what it sees, it's amperage rating should be at least double as well. At such currents the diode must be mounted on a heat sink meaning hope you never have an insulator to the sink short.

Assuming it's a kitchen hotplate, A diode say for example 1KV PIV 25 ampere would be hard to find. Stud mount with a few inches ^2 of heatsink with HV insulator, or pressed in meaning entire sink a shock hazard. Just not a great idea to do all this to properly engineer the idea of papaya.

Also woelens math is correct and therefore papaya's idea will not turn out as He thought. All He would do is burn out the element early while dealing with a fire hazard in the lab.

A lamp dimmer rated over a kilowatt to provide reasonable de-rating is just a bad idea. Dissipation and therefore heat is too great meaning only the transformer is the proper route.

Since the OP does not bother to come back in with bfessers requested information it's all moot anyway. Was He speaking of a kitchen hotplate drawing 12 amperes at 117 VAC, or one for chemistry with a much lower wattage? Who knows.

Edit to add: Being logical, how much did OP really save finding a US made hotplate? Obviously the step down transformer would make the most sense. Too bad the OP never bothered to answer any question by members after bothering us all with the thread. I think it's safe to assume no one would buy a cheap kitchen hotplate and pay shipping overseas. Thus leaving the conclusion it must be a chemical lab hotplate. Looking at a typical 120 volt example:

Cole-Parmer Stirring Hot Plate, Ceramic top, 12" x 12"
YO-04803-15 Power 115VAC 60Hz

I see no actual useful information for someone designing a lab and needing to calculate the power service. The spec should have been labeled 'voltage', not 'power'. No rocket science on the part of whoever put their site together. Nasco site same thing. I looked around both sites and it seems neither company bothered to state this important information. How many amperes. Cimarec same story. Even on models in the $200 to $300 range none gave either the wattage or amperage making this difficult to comprehend. Why do so many seem to think this is not important information. No I did not spend hours searching the sites, such information should be easily seen on the description page. Thankfully Thermo Fisher Scientific had employees with enough common sense to at least indicate the wattage which allows us to know the required value to pick a transformer with the proper ratings. Except at 750 watts we are right back at my initial thought of using a common kitchen hotplate to decide upon the proper rating of a step down transformer. Full circle expense would be high enough to safely assume the smart route is sell it and buy one designed for EU power. Nothing else makes sense, common or otherwise. I do not see the point in the OP's plan. Nor any savings.


[Edited on 8-27-2013 by IrC]

woelen - 26-8-2013 at 22:48

Quote: Originally posted by papaya  
How you managed to calculate double power woelen ? Diode strips the "half" of the wave, so ideally power is halved, even if peak voltage remains high. [...]
If you double the voltage, while keeping the load the same, then you take 4 times more power. You cut away half of the wave form, so what remains is 0.5*4 times the original power, hence double the power of a full 110 V AC wave.
Power is proportional to the square of applied voltage!

@IrC: Indeed I think that we have a very reliable power grid over here. Outages are very rare, I have a little server running in my house (this server runs my website) without UPS and it can have uptimes of a year easily.

[Edited on 27-8-13 by woelen]

phlogiston - 27-8-2013 at 12:22

I agree that a transformer is the most straightforward and best solution, but it is a little expensive. So expensive, in fact, that it may well be cheaper to sell this hotplate and get another one.

Admittedly it's not perfect, but I don't really see why a dimmer is such a very poor idea as a cheap alternative.
They are typically around 99% efficient, so energy loss/heat dissipation in the dimmer should not present a big problem. You can buy commercial dimmers for 2kw terrace heating, and I do have in fact an old lab hotplate myself that has a built-in triac-based PWM dimmer circuit for temperature regulation. Most dimmers can be freely adjusted to any setting, including 25% power, or 110V RMS voltage as desired, so the heat dissipation in the hotplate itself will be according to its design.
The only objection I agree with, as Woelen pointed out, is that the peak voltage will be somewhat higher than the 155V seen on 110V rms, but I would be surprised if it cannot handle a moderate increase in peak voltage.

TS, if you are still interested you should probably give us a bit more info, including the following:
1. Clarify what the hotplate is designed for and where you want to use it.
2. What is its power rating?
3. How is it designed internally?

[Edited on 27-8-2013 by phlogiston]

papaya - 27-8-2013 at 14:24

Quote: Originally posted by woelen  
Quote: Originally posted by papaya  
How you managed to calculate double power woelen ? Diode strips the "half" of the wave, so ideally power is halved, even if peak voltage remains high. [...]
If you double the voltage, while keeping the load the same, then you take 4 times more power. You cut away half of the wave form, so what remains is 0.5*4 times the original power, hence double the power of a full 110 V AC wave.
Power is proportional to the square of applied voltage!
[Edited on 27-8-13 by woelen]


You are right, I was confused saying that, because earlier I managed to reduce the power of a regular 800 watt hot plate (non lab) by placing a diode in series and a key in parallel to it so I could switch between normal/lower power that way (but this has nothing to do with voltage!). It works nicely and the diode is only 10A max. average current one with metallic casing which is not heat-sinked, it is placed inside the plate and gets very hot from the filament (just by itself it becomes only a little warm if operated outside) more than 100°C, but it served a long time without failure so diode doesn't need really to be a huge one in such things.

ScienceSquirrel - 27-8-2013 at 14:42

We have a similar system to Woelen in Jersey and France.
AC with three poles and an earth.
Most houses run on single phase eg one pole and earth at 230 V AC at 100 to 150 amp but three phase at 100 - 150 amp per phase is available for commercial and light industrial premises.
It is easy to buy boxes that change 230 V to 110V. These are often used on building sites or to run US equipment.