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jes25

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Midwest
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Electrician
Gentleman, What problems do you think would be possible in connecting a 60hz 230V window AC to 50hz 220V power supply, other than the obvious UL issues. The 220v is within the range on the nameplate. I imagine the compressor would run a little slower due to the 50hz power. This is on a military installation. Is there any other issues with the change in frequency?
Thanks, any comment appreciated.
 
It'll require more current and work less efficiently then the nameplate says.
 
Thanks for the comment. The article was helpful as well. I wonder how serious of a fire risk exsists due to the increase in amperage?
 
LarryFine said:
He doesn't mean an electrical installation. :)
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I just noticed that his location was "midwest" and he was talking about 50hz, which is where the puzzle started. I thought that perhaps there were some military bases in the midwest with their own 50hz systems. Aparently not.
 
jes25 said:
...I wonder how serious of a fire risk exsists due to the increase in amperage?
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i don't know that there will be an increase in amperage. V/H ratio is likely the same - compressor and fans turn slower, but I would not anticapate and increase in amperage. My expectation is the amperage would go down, cause the motors are doing less work (slower turning)

The compressor-motor is likely sealed so you won't be able to tell if it is overheating.

I'm guessing if it works at all and doesn't burn up within a few months, you are a hero.

Hook it up per NEC 527.3C. Make sure the overcurrent protection is good and within spec. Monitor the current to make sure it is within nameplate. Don't let it run unattended until you get some confidence.

Good luck. Stay safe.

carl
 
Less Coolling:

Less Coolling:

You will get less than the rated cooling with the compressor and fans running slower.
 
coulter said:
i don't know that there will be an increase in amperage. V/H ratio is likely the same - compressor and fans turn slower, but I would not anticapate and increase in amperage. My expectation is the amperage would go down, cause the motors are doing less work (slower turning)



carl
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The amperage is increased because I used my amprobe on it. Nameplate was 12 and it drew about 16. The same principle is stated in the link to article left by cadpoint on the top of the page. It makes sense that the increase in current and the lack of mechanical cooling will overheat the compressor and damage the unit.

I openly admit I don't know enough about motors to explain why the current goes up.
 
Jes -
jes25 said:
The amperage is increased because I used my amprobe on it. Nameplate was 12 and it drew about 16. ....
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Bummer - you were so close to being a hero.
jes25 said:
... The same principle is stated in the link to article left by cadpoint on the top of the page. ...
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The autor of that article did not do a very good job with the limitations of his explanation. Plenty of three phase 60hz, 460V motors are used on 50 hz, 385V - and they do just fine. You only get 5/6 the rpm, and 5/6 the Hp, but at 100% torque, the current is 100% nameplate FLA. The important part is to keep the volts to hertz ratio the same. Aparently that isn't the case with single phase stuff.
jes25 said:
...Nameplate was 12 and it drew about 16. ....
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Hummm. Not much of any way around that. Any chance your ammeter is calibrated for 60hz and is off high on 50hz? Probably not.
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jes25 said:
...I openly admit I don't know enough about motors to explain why the current goes up. ....
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I don't know much about single phase motors either.

carl
 
We had a 3 phase pump motor a while back drawing amps way over FLA (220 when should have been around 190). Turns out the generator feeding the unit was only generating at 57 hz. Sped up generator and it was an instant fix.
 
jes25 said:
Gentleman, What problems do you think would be possible in connecting a 60hz 230V window AC to 50hz 220V power supply, other than the obvious UL issues. The 220v is within the range on the nameplate. I imagine the compressor would run a little slower due to the 50hz power. This is on a military installation. Is there any other issues with the change in frequency?
Thanks, any comment appreciated.
Click to expand...

I believe it will be an induction motor in the compressor, and I'm guessing the window air conditioner is pretty basic, just a free running motor which is cycled on and off by a thermostat and there is no variable speed compressor with all the feedback and electronics associated with that type.

The compressor will turn at a 1/6 or 16% slower rate and the current draw should also be 16% less. I think the starting torque would be lower which could lead to motor stall, but I doubt it is an issue. The running cycles will be longer to achieve the same cooling.

EDIT: after some thought, this is not a free running motor (i'm no compressor expert BTW). The motor turns the piston each revolution, and it takes the same amount of energy to compress the coolant back to liquid, so the motor should draw more current per revolution. I doubt the manufacturers were generous enough to build your motor coils for the extra current, you will get extra heating in the motor.
 
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I just had this same thing thrown at me as 'they' wanted to send a 230vac 60Hz single phase motor/pump on a demo unit to China for a trade show where they have 220vac 50Hz.

I talked to several major motor mfgs and my local suppliers to confirm what I thought was true.

Since this sounds like a single phase motor, it may have a winding / capacitor that is switched in for starting, out for running. At 50Hz vs 60Hz, the rpm speed sensing switch will most likely not open up and that would be bad. High amps and heat bad.

What we ended up doing was to change our motor to a 3 phase one and run it at desired speed with a vfd.
 
Cody K said:
We had a 3 phase pump motor a while back drawing amps way over FLA (220 when should have been around 190). Turns out the generator feeding the unit was only generating at 57 hz. Sped up generator and it was an instant fix.
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Likely the voltage stayed up at rated spec, so the V/H ratio was up. This overexcites the motor, which saturates the iron, which drives up the current.

I worked on some Navy shipboard installations that used a steam turbine as a VFD - main coolant pumps for a pressurized water reactor. To slow down the motors, the turbine speed was reduced, down as far as 15Hz. The voltage regulator brought down the voltage in ratio, to 120V. Worked well. Although it kind of reminds me of the Flintstones.

carl
 
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