Hi All,
I have recently moved from Canada to the UK. I have not moved most of my fusor equipment over here yet, but I'm starting to work on bringing stuff over. However, one thing has occured to me... Running 120v/60hz pumps on 220/50hz AC....
My large rotary pump probably will never come over as I can just buy another one here if I need.. But I think it has taps on the motor to run at 230 and a different frequency might just mean a slightly slower speed that should not make much of a difference. However, I do have one of my other pumps in transit right now. It's a Tribodyn td-30/120 (see http://www.pchemlabs.com/product.asp?pid=2088).
What do you guys think about running this from a step-down transformer? I figure the turbo-drag stage should be fine as the controller will just conver the mains to DC to drive the brushless motor in the pump unit, however my concern is the diaphram backing pump that it's mated to inside. Will a diaphram pump intended to work for 60hz work fine on 50hz? Will it run slower? if that's the case, do you think the slower / lower pumping speed would make a significant difference on backing the turbodrag unit? Is there any danger of it being insufficient to properly back the drag pump?
If I do need to drive this thing at 60hz, what are my options? I have not been able to find any sort of phase converter for 50/60hz. I could build one by rectifying the 230, and then drive a step-down transformer at 60hz with a full or half bridge of mosfets (A modified sine-wave would be sufficient, I think...), but that's an overly complicated option... Or I could get a beefy 12v power supply and connect it to a 120v/60hz inverter... Any other suggestions?
Hopefully I'm worrying too much about it and the diaphram pump will run just fine from 50hz... I suppose there's no harm in trying it to see what will happen anyway. But any comments you can provide would be appreciated.
Thanks,
Troy.
Diaphram pump on lower frequency
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Troy Peterson
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Doug Coulter
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Re: Diaphram pump on lower frequency
You might find on close inspection that the pump/motor is already rated for 50hz, much quality gear is. Or that it's a DC motor in the first place. If it's a normal AC motor, it will run about 20% slower on 50hz, and get warmer because the series inductance it has will pass more current at the lower frequency. The slower speed probably won't matter too much, but the motor may get too hot, you'll just have to test that. Remember it can take awhile of running to find out how hot it's getting, since the heat takes time to reach the outside.
I run 100% off inverters here (whole place is solar powered). Modified sine inverters the size you might need are dirt cheap, probably cheaper than you could build, document, and maintain yourself. They will run most motors fine, but cap start large motors can be a real issue. I find that most motors make more noise, but also have more torque on the modified sine waveform here, and in fact, rather than throwing away my inverters of that type when I upgraded to true sine, wired them to my larger machine tools instead - they perform better than with "official" power(!). Then all you need is low volt high current DC to run the inverter - a battery and a charger work well for that, the battery acting kind of like a huge filter capacitor. The better, bigger inverters tend to be for 24v or more input. Xantrex makes the best, a SW 4024 runs my entire campus except for an air compressor and milling machine.
I doubt you need that - it will probably work fine on 50hz if the voltage is right. You might have to tune the exact voltage down a bit to keep things cool, but good quality scientific gear is usually a step above the usual consumer crap, and probably has some fudge available.
In my own system, FWIW, my large Pfeiffer "XtraDry" oil free forepump already has a converter drive (they say it was from a conveyor belt system) that ramps the pump speed up and down and does not care what the mains frequency is at all -- the way it came.
I run 100% off inverters here (whole place is solar powered). Modified sine inverters the size you might need are dirt cheap, probably cheaper than you could build, document, and maintain yourself. They will run most motors fine, but cap start large motors can be a real issue. I find that most motors make more noise, but also have more torque on the modified sine waveform here, and in fact, rather than throwing away my inverters of that type when I upgraded to true sine, wired them to my larger machine tools instead - they perform better than with "official" power(!). Then all you need is low volt high current DC to run the inverter - a battery and a charger work well for that, the battery acting kind of like a huge filter capacitor. The better, bigger inverters tend to be for 24v or more input. Xantrex makes the best, a SW 4024 runs my entire campus except for an air compressor and milling machine.
I doubt you need that - it will probably work fine on 50hz if the voltage is right. You might have to tune the exact voltage down a bit to keep things cool, but good quality scientific gear is usually a step above the usual consumer crap, and probably has some fudge available.
In my own system, FWIW, my large Pfeiffer "XtraDry" oil free forepump already has a converter drive (they say it was from a conveyor belt system) that ramps the pump speed up and down and does not care what the mains frequency is at all -- the way it came.
Why guess when you can know? Measure!
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Chris Bradley
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Re: Diaphram pump on lower frequency
TroyPeterson wrote:
> I have recently moved from Canada to the UK.
{How unfortunate for you!! }
> What do you guys think about running this from a step-down transformer?
It should be fine, but depends on how much 'head room' you have for this. viz. if you have a 4-cylinder pump you should do fine, but a 2-cyl may already be making the drag pump work a bit hard.
I have acquired two such pumps over the last couple of years, 2 and 4 cyl types and both designed for the lower V/60Hz. I test-ran them with a variac and they do run a bit faster if you put more volts in them, but I got the feeling they were running 'harsh' if you put too many volts into them. I also acquired a 12V-115V 60Hz inverter for operating them, too, when one came up on ebay cheap.
AFAIK turbo pumps will always pull a better vacuum with an equivalent lower backing pressure.
> I have recently moved from Canada to the UK.
{How unfortunate for you!! }
> What do you guys think about running this from a step-down transformer?
It should be fine, but depends on how much 'head room' you have for this. viz. if you have a 4-cylinder pump you should do fine, but a 2-cyl may already be making the drag pump work a bit hard.
I have acquired two such pumps over the last couple of years, 2 and 4 cyl types and both designed for the lower V/60Hz. I test-ran them with a variac and they do run a bit faster if you put more volts in them, but I got the feeling they were running 'harsh' if you put too many volts into them. I also acquired a 12V-115V 60Hz inverter for operating them, too, when one came up on ebay cheap.
AFAIK turbo pumps will always pull a better vacuum with an equivalent lower backing pressure.