60Hz to 50Hz Appliance

Hello,
I was wondering if an American Made Referigrator rated 120V 60Hz could work
efficiently with the use of a step down transformer in Africa where the
electricity is rated at 240V 50Hz.
Thanks,
Reply to
Kissi Asiedu
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It's not recommended to do so. The motor will not perform as intended.
Reply to
Tom Biasi
As usual, the answer is: It depends.
If you can, contact the manufacturer to get more information.
You can try monitoring the current to see if it becomes excessive.
If the refrigerator does not have to work hard, You might want to get an transformer or autotransformer to change to 100V. That would mean that as the transformer rotates at the lower speed, current for the same output torque will be close to what it would be for 60Hz. Bit do not expect the refrigerator to work at full capacity.
Reply to
Salmon Egg
Good way to burn your house down...
The change from 60Hz to 50Hz is an issue with heat. Running a synchronous electric motor at low voltage is also an issue with heat.
The transformer does not rotate, and the lower voltage would not change the speed of either the transformer current or the motor rotation.
Reply to
Floyd L. Davidson
The first thing to do is look at the nameplate on the appliance. Most modern appliances are designed to work on both 115 volt 60hz and 100 volt 50hz power. If you post the manufacture and the model number we might be able to find that information for you if you cannot.
Reply to
Rich.
I do not think you know much about modern refrigerators. They usually use induction motors lubricated by the refrigerant. There are no slip rings or other electrical connections with rubbing parts.
If the refrigerator manufacturer is not cutting corners too much, there should be enough iron and copper to prevent such catastrophe. Even if the motor cannot run at 50Hz and 120V. it should be able to run no load at 50Hz/100V at about the same CURRENT as at the 60Hz/120V. The only problem comes when you add the load of the compressor. If you get satisfactory performance without exceeding the the rated current for 60Hz/120V, you should be ok. That is, for 50Hz operation, do not exceed a VA input more than 5/6 of the VA allowed at 60Hz operation. Just take the resultant loss in performance.
Reply to
Salmon Egg
There is merit in what you say, however, the efficiency loss will manifest as heat since the reactance is not optimal and the starting capacitor will not be doing it's job properly. And manufacturers do cut corners considerably to compete in the US market. I still would not do it.
Reply to
Tom Biasi
Seconded, back in early history one of my first electrical tasks was fitting an auto tranny to imported American Frigedaire refrigerators to compensate for our 50hz supply.
Reply to
Rheilly Phoull
Salmon egg has it right- Motor control generally follows a constant V/f ratio. The efficiency hit is not significant as the load current content at rated torque will be roughly 10% higher but the magnetizing current (roughly half the total current) will be lower. Heating and efficiency will be about normal but the motor cooling will be less effective due to the lower speed. Starting transients are not a consideration in terms of losses and efficiencies. Will the motor run hotter- maybe - because cooling isn't as good at the lower speed
Slip will be a bit higher so speed will be a bit less than 5/6 the rated full load speed. Yes, starting current will be higher and the starting capacitor will not be optimum and if starting is marginal (However after the days of brownouts killing fridge motors in the past, I expect that newer fridges have a bit more capability in this respect).
Reply to
Don Kelly
(However after
If he does do it I hope your expectations are correct.
Reply to
Tom Biasi
In one of my responses, id did say that the transformer rotated.While that is incorrect, it is not far off base. An induction motor is a transformer with a rotating winding. That is how you get slip. sometimes, I just do not think of a transformer and a induction motor as being fundamentally different.
There also is an induction regulator which is an induction motor which is blocked from turning freelhy and serves as a variable transformer.
Reply to
Salmon Egg
If you use a polyphase wound rotor machine with the rotor and stator windings independent- then, depending on the position of the rotor, you have a phase shifter. In this case the output voltage magnitude doesn't change. If you take the same machine and connect the windings as an autotransformer you have your regulator. I have used the former but a ganged 'variac' is more efficent as the magnetizing current is much lower. It is said that the "variac' has discrete steps in regulation vs a smooth variation for the regulator --but-- the mechanical adjustment for either may result in discrete steps.
There have been many, sometimes weird, devices based on the induction motor- and, before modern electronics, many of them were intended for speed control.
Reply to
Don Kelly
I vaguely remember something called a "phase shifter." It had something to do with efficient operation of an induction motor far off synchronous speed. IIRC it used one or two additional rotating devices to maintain torque and/or decent power factor. Do you know anything about that, Don?
Reply to
Salmon Egg
The phase shifter I referred to would simlpy change phase- it had a 1:1 turns ratio. However using it as an autotransformer would provide a variable voltage I don't know how a device external to the motor would improve efficiency of the motor. However- what you refer to may be a Schrage motor which fed back from the rotor (apparently involving a second rotor and stator winding to convert from slip frequency to line frequency (and with brush shifting in between to shift phase as needed. )and would involve some phase shifting. This machine could maintain torque over about a 10:1 speed range, possibly with decent efficiency(?) It was bulky and complex- I did run one when an undergrad about 60 years ago and never since met one, thankfully.
Reply to
Don Kelly
Tom, you did bring up some good points and these lead to Valid "ifs and buts" -all related to starting. If the load was a fan or similar, there would be no problems but with a compressor, effects of frequency variations with capacitor start may certainly reduce motor starting torque and if there is back pressure ?-a problem. I had thought a fridge compressor did provide a high back pressure at start but it appears that I may be wrong about this- it makes a difference. In addition, there could well be a problem with the centrifugal switch If it's normal opening speed was too high (which is a good possibility), then the starting winding wouldn't be disconnected-not good- smells expensively funny. The transformer, if 60Hz would have to be 288/120V -say 1KVA. Considering the cost of purchase, shipping, transformer etc- it may well be that one should purchase a 240V 50Hz fridge in the first place. A quick search indicates that every major manufacturer of fridges (us and elsewhere) have 240V 50Hz models - some sources have 240V 50 Hz compressors which could replace 120V 60Hz units.
So it really comes down to experience when trying this.
Reply to
Don Kelly
Don, As usual you let logic prevail. My recommendation not to do it was largely based on the practical aspects of being able to find a local version of what the OP wanted vs. the known problems associated with doing this. Combine this with an increased ambient temperature (ie. Africa) I recommended against doing it. Your analysis is certainly noteworthy however.
Reply to
Tom Biasi

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