Frequency question

You are dead on Greg. The motor will produce more power, for the same voltage, and will likely overheat. Same torque (roughly), higher speed. The different fan blade *will* alleviate the problem, and could be selected to move the same amount of air though.

He could also use a variable frequency drive, if the motor is large, and prevent the problem. Alternatively, he could drive the fan with a belt and select a different pulley-set for the different frequencies.

David A. Smith

Contrary to your other responders, assuming the fan motor is a commutator type (as it's likely to be) there will be almost no effect on operating speed, and the windings may run a little cooler.

Typically these types run DC to 100 Hz without dramatic consequences.

Brian Whatcott Altus OK

Yes the voltage is the same - 110V

If you run them with the original fan then they will be developing more power than at 50 Hz, so they will run hotter. So you could fit a new fan optimised to absorb the same power at the new speed. This is unlikely to shift as much air as the old one.

Now, the above could be entirely wrong, I'm a mechie, not a sparky.

Um, just a wild stab in the dark, is the voltage the same for both the

Cheers

Greg Locock

I'd guess that a fan coil motor would be open frame shaded pole AC. No commutator, no capacitor.

Versions built for 50Hz will surely overheat on 60Hz. A suitable resistor in series would reduce the current, and the heat, and the power and the airflow. So, it wastes energy. These motors are not paragons of efficiency in the first place.

Which has the side effect of allowing them to tolerate odd power supplies, like chopped AC, or even square waves. So you could run them with a cheap AC triac speed control, or rectify the 60Hz to DC and feed them a 50Hz square wave from that.

If you can chop 160VDC at 50Hz, you can chop it at other frequencies, too, and have variable speed with decent torque, and some acoustic noise.

-Mike-

Dear friends thank you for your responces. I am marine engineer and I had never thought that I would be involved in the above subject but I did. Fortunately it was a quotation for the installation of new small a/c system on an existing ship of 60Hz power supply with fan coils of 50HZ as manufactured in my country, which we wisely postponed till things clear out. A good responce came from an elec. eng. forum as follows.

"At the higher frequency, the motor will spin faster. This will increase the load on the motor and could cause it to fail quite quickly. It depends on how well loaded it is when running at 50 Hz. Typically, the load will increase by the speed increase squared. i.e. a 20% increase in speed willlead to a 40% increase in load. At the higher frequency, if the voltage is the same, the flux in the iron will be reduced, reducing the torque capacity of the motor. If the combination is not designed for use at 60Hz, you could have a problem." So we decited not to propose a converter but to find fan coil units with

Oh well, the intention was to help, but I must have been dozy when writing the post below.

Only auto fan motors are found with commutators, which are relatively insensitive to drive frequency. But since when does a 50Hz drive show up in autos?

Maybe this next thought may be slightly more pertinent. Variable frequency drives are showing up for commercial AC fan motors. This might be worth considering.

Brian