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Forum topic by EMVarona posted 415 days ago 568 views 0 times favorited 7 replies Add to Favorites Watch
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EMVarona

436 posts in 1437 days


415 days ago

Topic tags/keywords: electrical motors voltages and cycles question lathe

I have a 220 v 60 cycle lathe motor however our line is 220 v 50 cycles. It runs but everytime I turn it on, I have to rotate the shaft to help it. The lathe has a variable size pulley to change speeds. Unfortunately it works only in one speed. Is there a way of adapting this motor to the 50 cycle line?

-- Ed "Real happiness is one that you share."


7 replies so far

View Jim Jakosh's profile

Jim Jakosh

11072 posts in 1707 days


#1 posted 415 days ago

Hi Ed. I posed your question to an electrician friend of mine. We’ll see what he says.
Does the motor have a capacitor on it for starting?
Usually, if you have to roll the motor over to start is because the starting capacitor is bad.
I’‘ll see about the 50/60 cycle business from my buddy, Jim.

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

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REO

581 posts in 675 days


#2 posted 415 days ago

it should start just fine but run slower.sounds like jim said = capa

View Jim Jakosh's profile

Jim Jakosh

11072 posts in 1707 days


#3 posted 415 days ago

Here is what I found , Ed.:

Also, if it has a starting capacitor, have it checked. If you have to roll it to start it, that cap is usuallyl bad. Also, one thing I found out on my lathe. I was burning out starting capacitors every3-5 month. When I got the last one, the motor shop guy told me to use a capacitor rated at 220 instead of 110. That worked and I have not changed that capacitor in 3 years now. If you get one, get a 440 rated one!!

Here is the answer!

Using a 60Hz motor in 50Hz duty. w) It will turn 20% slower. x) Cooling will drop dramatically. y) The load’s horsepower requirements will drop, possibly dramatically. z) V/f will increase possibly causing a large increase in current draw.

Make sure the load will still do what is required of it when running slower. For instance, a fan load would now move less air. Still enough?

The cooling will reduce dramatically. Is it enough to matter? This depends on how the load has decreased. If the hp requirement dropped because the load has decreased the current will drop and less heat will be released internally. You would want to take temperature measurements until the motor reaches a steady state temperature running in its new frequency application.

The motor’s hp will drop because hp is a function of speed x torque. The motor’s torque doesn’t change but its speed has dropped so it is now a lower hp motor. If you change pulley sizes to return the load to its original speed your motor will likely be undersized, possibly seriously. Example: A 10 hp motor is now an 8 hp.

The most serious issue is the V/f issue. The V/f will increase. Likely enough to cause a large increase in the motor’s current. This coupled with the reduced cooling may cause rapid overheating. However the V/f problem can be fully mitigated! You reduce the voltage to the motor by the amount required to return the V/f back to its original value. This removes the hazard of excess current from an increased V/f.

Example: A 60Hz 240Vac motor is going into 50Hz service. V/f = Y Hence: 240/60 = 4.0

So if Y x f = V then by plugging in the new frequency of 50 we see:
4.0×50 = V
V = 200 Running the motor at 200V at 50Hz will remove the V/f problem.
New voltage = Old voltage x 50/60
New speed = Old speed x 50/60
New Horsepower = Old horsepower x 50/60
Note: This would instead be 60/50 for a 50 to 60 Hz conversion.

Another way to think of this is:

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

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EMVarona

436 posts in 1437 days


#4 posted 414 days ago

Thanks, Jim. I really haven’t checked the capacitor. I’ll do that.

-- Ed "Real happiness is one that you share."

View Shawn Masterson's profile

Shawn Masterson

1243 posts in 550 days


#5 posted 414 days ago

I am not an expert, but I wonder if a VFD (variable feed drive) would fix this. the way I understand it a VFD takes the AC power and converts it to dc then makes that into whatever you need. It would also give you variable speed. I know people use them to make 3phz, but I have seen videos where a VFD is used for the sole purpose of variable speed. It may be just what you need.

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Mainiac Matt

3837 posts in 930 days


#6 posted 413 days ago

Motors designed to run on 50 Hz have magnets with more “reluctance” (kind of like magnetic resistance), which enables them to generate adequate power with the slower alternating current frequency.

50 Hz motors will run just fine on 60 Hz power.

However, 60 Hz motors will suffer a decrease in power when run on 50 Hz.

-- Pine is fine, but Oak's no joke!

View EMVarona's profile

EMVarona

436 posts in 1437 days


#7 posted 411 days ago

Thanks, Guys for the information. These are things I am completely ignorant about.

-- Ed "Real happiness is one that you share."

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