# 50hz motors on 60hz



## Peewee0413 (Oct 18, 2012)

How was the transformer wired? What all was in the circuit?

Sent from my SM-G998U using Tapatalk


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## backstay (Feb 3, 2011)

dspiffy said:


> Here's a question I get often. What's the cheapest way to make a 230v 50hz motor on 120v 60hz?
> 
> I know the CORRECT answer. Variable voltage, variable frequency power supply.
> 
> ...


Harmonics would be my guess.


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## paulengr (Oct 8, 2017)

If it works properly at all at 60 Hz, expect RPM to go up 20% over name plate. Since the motor has a thermal limit HP is fixed but max continuous torque is going to decrease to 83% if you feed it “240” or “220” or whatever you call it. Assuming single phase here. Set your overloads to 83% of name plate. Motors will tolerate up to 10% on the voltage.

Capacitor ratings are proportional to frequency with AC so all the caps should be decreased to 83% of the original size.

So if you take these two steps it should run just fine if you are talking about single phase motors.

If you truly want to run on 120 V then you’ll need a pretty large transformer. I’d suggest HP x 7.5 = kVA rating if you try to step up 120 to 230. If you just go to 3 phase there are voltage doubler VFDs that convert 120 single phase to 230 3 phase up to 2-3 HP. A three phase motor of the same HP and RPM is considerably cheaper than single phase but the drive won’t be cheap. The drive adjusts both frequency and voltage and replaces the whole starter. You can just run it at 50 Hz or almost any other frequency up to a couple hundred Hertz if the bearings will take it.


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## oldsparky52 (Feb 25, 2020)

dspiffy said:


> Here's a question I get often. What's the cheapest way to make a 230v 50hz motor on 120v 60hz?


What applications are we talking about that you get this question "often"? 

You are talking about a permanent installation or for a day or two until the right part comes in? Just a motor or a whole piece of equipment? 

Just curious.


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## oldsparky52 (Feb 25, 2020)

Lots of articles about this and pretty much it seems to me that it's something you should try to avoid w/out the correct equipment.


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## dspiffy (Nov 25, 2013)

oldsparky52 said:


> What applications are we talking about that you get this question "often"?
> 
> You are talking about a permanent installation or for a day or two until the right part comes in? Just a motor or a whole piece of equipment?
> 
> Just curious.


I used to work in a museum that specifically dealt with old fans, motors, machinery, etc. I still get people that collect old fans emailing me with questions (I also collect old fans.)

I also used to work on music equipment. Hammond Organs and Leslie speakers use both shaded pole and synchronous motors. The synchronous motors HAVE to have the frequency on the nail but the others are more forgiving. They make frequency converters specifically for the run motors, but not the others.

In both cases, it would be a semi-permanent solution, but not used heavily. Unless someone is talking about retrofitting a European product for constant use in their home.

Someone eMailed me yesterday asking about installing a collectible German ceiling fan in his US home. Ultimately I told him to transplant a US motor, but it got me thinking.


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## u2slow (Jan 2, 2014)

As already covered, most 50hz motors usually tolerate 60hz at reduced load/torque.

You may not have oversized the transformer enough - inrush and power factor.


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## SWDweller (Dec 9, 2020)

I do not run into this often so I just put a drive in front of the motor and set the Hz in the drive.


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## sayedmhussein (11 mo ago)

According to our formula speed = 120 x Frequency / No. of Poles.

So when you run a 50 Hz motor on 60 Hz power supply expect 20 % increment in the rotation speed, so you need to check your load if a change in speed will cause a change in torque characteristic of the load or the load will be affected negatively.


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## JRaef (Mar 23, 2009)

A fan will increase the LOAD on the motor by the CUBE of the speed change. So running a 50Hz motor on 60HZ will increase the speed to 120% of its design, that will increase the air flow and thereby the LOAD on the motor by 1.20 cubed or 173%. So for example if the fan has a 500W motor, you can assume that the fan load required somewhere around 500W, but by running the fan on 60Hz, the load becomes 865W, but you still have a 500W rated motor, so the motor overloads and burns up.


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## paulengr (Oct 8, 2017)

JRaef said:


> A fan will increase the LOAD on the motor by the CUBE of the speed change. So running a 50Hz motor on 60HZ will increase the speed to 120% of its design, that will increase the air flow and thereby the LOAD on the motor by 1.20 cubed or 173%. So for example if the fan has a 500W motor, you can assume that the fan load required somewhere around 500W, but by running the fan on 60Hz, the load becomes 865W, but you still have a 500W rated motor, so the motor overloads and burns up.


Air flow is only square of speed, not cube.


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## glen1971 (Oct 10, 2012)

paulengr said:


> Air flow is only square of speed, not cube.


Isn't the 3rd Fan Law:

HP2=HP1x(RPM2÷RPM1)^3 ?

Which, using JRaef's numbers:
HP2=500 watts x(1.2)^3, where 1.2 is the speed increase from 50 to 60 hz,
HP2= 864 watts


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## paulengr (Oct 8, 2017)

glen1971 said:


> Isn't the 3rd Fan Law:
> 
> HP2=HP1x(RPM2÷RPM1)^3 ?
> 
> ...


I don’t disagree with power.

I’m wrong too.

Pressure is proportional to the square of RPM.

Flow is proportional to speed.






Fan Affinity Laws


The affinity laws can be used to calculate resulting volume capacity, head or power consumption when speed or wheel diameters are changed.




www.engineeringtoolbox.com


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## dspiffy (Nov 25, 2013)

FYI I am reading all of these replies and learning.


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## JRaef (Mar 23, 2009)

I just said "air flow increases", the reference to the cube increase was related to required power.

HP2 = HP1 x (N2/N1)cubed 
Where N1 = old speed and N2 = new speed


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