220V to 110V

[georgeten]

I want to use a water pump from US in Europe. Using a step-down transformer 220V to 110V causes the pump to heat and thermal protection trips. As well it will vibrate and it's power seems reduced.

Please confirm if the following setup will work:

Socket (out: 220VAC/50Hz) ...... Power supply (out: DC12V/10A)......Pure Sine Inverter (out: 110V/60Hz/180W)........Pump (110V/60Hz/30W)

Thank you,
George

 

[bychon]

I would generally refuse to confirm that a setup will work after you have confirmed that it doesn't work, and in this case, I can see that the motor uses 30 watts, but the DC supply is 24 watts. Thus, I confirm that you have confirmed that it doesn't work.

 

[bychon]

Oops...how did I see 2 amps on that 12 volt supply?

 

[georgeten]

I edited the PS specification, typed them wrong.

The initial setup which did not work was:

Socket (out: 220VAC/50Hz) ...... Transformer (220V/50Hz to 110V/50Hz) ........Pump (110V/60Hz/30W)

Thus the issue was the frequency.

 

[bychon]

I gotta have my glasses checked!

but I still can't confirm that a circuit works after you have confirmed that it doesn't work.

 

[georgeten]

I got high expectations that it will work with the pure sine inverter, my doubt is if I can connect it directly to the PS without using an intermediary battery

 

[bychon]

If the 12v supply is a 50 Hz rectifier, it may need some more capacitance on the output...remember, a battery is a form of capacitor. If it's a high speed switcher, it will track the load, just fine...I think. Try it. You seem smart emough to pull the plug quickly if it chatters.

 

[Hero999]

I'm surprised the transformer didn't work, the pump must not have liked the lower frequency.

Yes, using a 12V PSU and a pure sinewave inverter should work but it's not very efficient.

Is it possible to replace the pump motor with a 220V 50Hz unit?

Another option is a motor/generator set but at that size, it's probably no more efficient than the DC PSU and inverter idea.

 

[MikeMl]

Another idea is to raise the voltage to the pump, even though it seems counterintuitive. I used to work for a company that exported equipment to 50Hz countries. Raising the voltage to the pump motor from say 110V to 130V will cause it's line current to decrease by the inverse percentage (i.e. 110/130 = 0.85). Since heat losses in the motor are proportional to I^2 (0.85^2 = 0.72), the almost 30% reduction in heating will let the motor work.

 

[georgeten]

Unfortunately the 220VAC model is not yet available for this pump. I spoke with the manufacturer and they expect the 220V model in a couple of months.

Increasing the voltage to 130V made is worse. The pump tripped in less than 15mins, compared to ~30mins with 120V/50Hz.

This pump seems very sensitive to the frequency.

Still waiting for my pure sine inverter to arrive. I will post the results by then. It seems that I don't have any other options left.

Thanks all for your replies

 

[MikeMl]

What does the rating plate on the pump motor say?

 

[georgeten]

Rating plate on motor says 120V AC 60Hz 20W

 

[crutschow]

Another idea is to raise the voltage to the pump, even though it seems counterintuitive. I used to work for a company that exported equipment to 50Hz countries. Raising the voltage to the pump motor from say 110V to 130V will cause it's line current to decrease by the inverse percentage (i.e. 110/130 = 0.85). Since heat losses in the motor are proportional to I^2 (0.85^2 = 0.72), the almost 30% reduction in heating will let the motor work.

It's not only counterintuitive but is contrary to what can happen in a 60Hz motor operating on 50Hz. The problem is that if the motor is marginally designed, the magnetics will saturate at 50Hz causing the magnetizing current to increase significantly and overheat the motor, as the Op noted. Increasing the voltage will only make that worse. Lowering the voltage in proportion to the change in frequency however, can help (to 50/60 x 120 = 100V). The motor will draw higher current for a given load, but as long as the magnetics don't saturate, it's temperature should stay within limits, particularly if the motor is driving less than full load.

 

[georgeten]

Indeed, running the pump at 96VAC/50Hz helps; it starts heating up after 2 hrs of operation. I presume it will continue to heat-up and finally trip again. Maybe if I could run it below 90V it would not reach the trip threshold.
The drawback is that it's power is decreased a lot, making it useless for the operation. It's a salt water tank protein skimmer pump.
As I posted before, salvation might come from the inverter, hopefully.

 

[MikeMl]

The 60Hz motors that ran better on a higher voltage when operated on 50Hz were 1/2, and 3/4 HP induction motors. I'm guessing that the 20W motor is a shaded pole type, and if it saturates at 50Hz, it makes sense that it heats more at higher applied voltages.

 

[georgeten]

The pump works perfectly with the 120V/60Hz/180W pure sine inverter supplied directly from a 10A 12VDC power source.
Thanks all for your replies and suggestions