Znoble
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So I goofed...
My very fist hotplate/stirrer combo just came in from india, and I had an "I'm an idiot" moment where I realized that they use 250 volt outlets in
india. I'm looking at spending another $20 on a 120v/240v upconverter (still only spent $130 in all), but I don't know if the different frequencies
used in the different countries will render the stirring unit worthless. Any advice? Should I just sell it on ebay and make it someone elses
problem?
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elementcollector1
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It's worth a try, even if only to ascertain this for other people. If you can't use it, sell it again.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Magpie
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What is the nameplate frequency?
The single most important condition for a successful synthesis is good mixing - Nicodem
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Znoble
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could you explain what you mean? I figure that the stirring part of a hotplate stirrer would work in a similar way to a motor, namely by alternating
current to induce alternating magnetic polarities at a particular frequency, causing a magnet in the center to turn. If a motor was designed to
operate at 50hz (india), would it work at 60hz (us)?
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bfesser
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Most hotplates and stirrers have nameplates on them somewhere which will list the operating voltage, frequency, and other specifications. If you can,
post a photo.
Example nameplate:
[Edited on 12.12.13 by bfesser]
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Znoble
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My jank indian hotplate doesn't have one. I asked my dad (he's an engineer) if a different frequencies would render the stirrer function useless, and
he said it just might stir a little slower or faster. I just bought a power converter, we'll see how this flies. I might have just found a source
for cheap, new hotplate/stirrer combos 
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
quote]
[Edited on 12.12.13 by bfesser]
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Magpie
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That would be my guess also, ie, it might work fine but just run a little faster, like at 60/50 th of the expected speed.
But we have some electrical engineer members and others skilled in this field who should be able to give us much better answers, w/explanations, than
I can offer.
[Edited on 12-12-2013 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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zed
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Maybe work, maybe no. If it is a simple machine probably ...Yes! If it has some sophisticated electronics inside....No! Unfortunately, many
formerly simple devices, now contain a little bit of computer wizardry within. These machines are very conservative. No change!
A little variation in voltage or cycle, just doesn't compute properly.
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Tsjerk
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My experience is that using a device designed for 240V works on 120V but only with a quarter of the power, I can't recall exactly why it is a quarter
and not half but somebody ones told me and an experience with a hairdryer brought from Europe to the US convinced me he was probably right.
The frequency is the same though so that shouldn't matter, they always state it as 50-60 Hz. An apparatus designed for 120V plugged in at 240V will
give problems though, as the internal resistance is to low so the amperage will go up.IIRC
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Magpie
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Here's the reason you only get 1/4th the power:
E=IR (ohm's law); I=E/R
P=EI=E^2/R
R(resistance) is the same in both cases.
In the first case P=[(240)^2]/R
In the 2nd case P=[(120)^2]/R
[(120)^2]/[(240)^2] = (120/240)^2 = (1/2)^2 = 1/4
The single most important condition for a successful synthesis is good mixing - Nicodem
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Znoble
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Okay, so update on this. My voltage step-up converter came in the mail today, and I immediately plugged it in and turned it on. The fuse on the
converter blew. I pulled it out and saw it was 1.3 amps, and the hotplate takes 6, so I went out and bought a 6.3 amp fuse (the highest they had for
that particular size at radioshack), and plugged it in again. Lo and behold, there was heat! And stirring! And a godaweful burning plastic smell...
I looked over at the converter and it was smoking. So much for that experiment... I'm going to do one of two things:
1. we have a 250v outlet for washers and driers in my house, I could try to convert the power cable to go into that
2. bum off the hotplate on ebay
[Edited on 17-12-2013 by Znoble]
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Magpie
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Fuses are sized by the designer/manufacturer to protect the device. I guess you learned that the hard way. But you did demonstrate that the stirrer
will work at 60Hz. If you can plug in to that 250VAC outlet, which you can do by buying the proper plug, you will be in business. 
-------------------------------------
Edit: If a 250VAC stirrer is constructed the same way as a 120VAC stirrer then there will be a hot wire (normally black) and a neutral wire (normally
white). There likely will also be a ground wire (normally green). I think that if the two 250VAC hot wires from the new plug are connected to the
stirrer hot (black) and neutral (white) wires, respectively, the stirrer should perform normally. The ground wire (green) should be connected to the
ground wire coming from the plug.
This would be the way I would do it. Comments/corrections from those with a better understanding would be helpful here.
[Edited on 17-12-2013 by Magpie]
[Edited on 17-12-2013 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Master Triangle
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Pop the thing open and have a look at the wiring, if the heaters and motors have two coils in series then you can just put them in parallel and they
will run straight off 120V. With heaters that will always work if the heaters are of the same resistance, but the windings on a motor are not always
intuitive, post a picture of them to get opinions.
Although if you actually have a 240V outlet and it is a convenient place then just use that, look up plug layouts and mains wiring colour codes so
that you don't fry it. As far as I understand 240V outlets in 120V countries are actually two phases so there is no neutral. (My country uses a
civilized 240V system, so don't trust me)
Also, just try connecting it straight onto 120V, you won't be overpowering it so it shouldn't overheat or anything.
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