Does it damage a motor that is made to run at 60 cycles if it is run at 50?
I was talking today with a woman whose family owns a house in Barbados that I have rented five or six times. Last year the three BR fans were all out. She told me that they had been bought in Canada and taken there, but they bought new ones there and she hoped the problems were over. They had remote controllers and the new ones will have pullstrings. I speculated that the electronics went wonky from constant being shaken, but she speculated that it was the wrong frequency that destroyed them. I could see that they might run at only 5/6 speed, but it is not obvious that that would damage them. Does any Doper know?
Some airplanes I fly are limited to certain RPM ranges. I don’t mean the maximum redline - I mean certain intermediate speeds that would be normal for other aircraft. From what I’m told, running them in the forbidden zones could set up an unfavorable harmonic with the airframe and cause shaking.
No. I can’t find a cite, but me, as an Electronics Technologist says it shouldn’t make a difference one way or another. Slight difference in power factor? Perhaps. Any notiable difference? No.
Nope, not a problem. I worked a lot with variable frequency controllers that allowed you to adjust the speed of electric motors by controlling the frequency of the inccoming AC. If you get too slow, the motor can’t overcome internal friction and it won’t spin…but a motor isn’t an IC chip…it’s wire and a magnets.
Most electric fans use an AC induction motor (shaded pole type). Those are generally not harmed by a variation between 50-60Hz.
Possibly the electronics in remote controllers could be, but unlikely – they probably run on 2-5 volts DC power (a battery in the remote, and inside the fan a power supply that converts the mains power to low-voltage DC).
One minor problem is that they choose the thickness of the laminations - the separate layers of silicon steel - used to construct the cores of the electromagnets on the basis of how much inductive heating will result. The higher the frequency, the thinner they need to be to create the same amount of heat. It’s because of how large a loop you can have inside the thickness of the lamination, that acts like a shorted loop of copper in the winding would. For this reason, a motor designed for the 20 Hz power used on some railroads would overheat on the 60 Hz power we give to houses. I know that going the other way, using low frequency on a thin lamination, is expensive in the sense that making the laminations thinner costs more, and it’s wasted when they don’t need to be as thin as they are. I think there’s some other thing that goes wrong, too, but don’t remember what it is.
In any case, I doubt that the motors themselves or the controls (which would be using some kind of DC power supply) would mind going from 60 to 50. The only specific issue I can think of is that some DC power supplies use a capacitor to couple the line to a bridge, which reduces the voltage without a transformer and without wasting energy or generating heat. In this case, 50 Hz replacing 60 would do the voltage what dropping 120 V to 100 would do, so maybe there’s a little brownout happening in there. But AFAIK building DC power supplies this way isn’t very common, perhaps because capacitor shorts drive the power supply bridge input to +/- 180 V or so, which is dangerous.
Given that its Barbados, I’d suspect salty and humid air as a culprit. And perhaps their power distribution system has more/bigger voltage spikes than one would like (which could be bad for more sophisticated controlling systems).
Many interesting answers, which don’t quite agree. Still it seems unlikely that it could be a serious problem. I do not understand this V/f business. Exactly why would a fan, presumably turning at 5/6 the speed of its design parameter, draw more power, rather then less. I should have mentioned that the voltage is the same nominal 110 that we have here.
Here is an amusing story. After posting the question I tried googling it. I should have tried that before raising the question, but then I wouldn’t have the story to tell. The first hit, was ask-wiki which had the exact question, but the answer was useless: “Ask a local electrician”. What skill set would a local electrician have that would be relevant? It is an electrical engineer that is needed. Even “Ask the manufacturer” would be better, but you would probably have to speak a Chinese language. Clicking a few more links, I eventually came to a site called (I think) Ask-Yahoo.that had a link to my question. I clicked on this and it led directly to my question on the board! This probably within an hour or so of my having posted it.
A fan running at 50 Hz would draw more current than a fan running at 60 Hz because of the inductive reactance (XL) in ohms.
XL = 2 (pi) f L
f = frequency
L = inductance of coil
So as the frequency decreases, the amount of reactance (opposition to alternating current) also decreases. Decreased reactance results in more alternating current flow, which results in a higher power consumption.
This happens all the time on some of the carribean islands that operate at 50hz and people bring down appliances that were purchased in the States- they all burn out prematurely typically due to overheating issues.