Running 50HZ design on a 60Hz supply 3

[airwin27]

Good day!

I would like to ask a help from experts here about something that tickles my mind. We have a machine with a single phase motor 220V/50Hz, but our frequency here is 60Hz. Will it have any problem on its operation? Our machine is located on an area with a room temperature of 7-15 degrees centigrade. Upon running the machine, it generally stopped. As we turn the machine off and put it into rest, a minutes or an hour, we turned it on again and it functions well. But after a while, the machine shuts off again. May I ask what would be the cause of an abnormal function of my machine?
Thank you & hoping for your prompt help.

 

[DRWeig]

Check the FAQ:

http://eng-tips.com/faqs.cfm?fid=1224

Welcome to eng-tips!

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[itsmoked]

You haven't said if your motor is single phase or 3 phase. I'm going to guess it's single phase. That would be the only explanation for it stopping and eventually re-starting. It has a thermal overload buried in the windings (since it's single phase). It's overheating and tripping off. After cooling enough it will restart again.

It's overheating because it's running 6/5ths faster than it's supposed to due to the frequency increase. That's causing the load to increase over its design by 1/6th or more, possibly MUCH more.

Solve it by changing the gearing of the machine to reduce the machine operation back down to the original 50Hz speed it was running at. If it's impossible to re-gear it come back and we can help you come up with an alternative solution.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

The motor may also have a fault that has nothing to do with the frequency.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

He did say it is single phase.

The problem is not just the speed however, unless the motor is on a centrifugal pump or fan, it is more likely the ratio of voltage and frequency. You are giving this motor a lower V/Hz ratio than it was designed for, so the motor is producing less torque and at the same load and therefor is working too hard. So if reducing speed reduces the load, then yes, that will work. But many types of machines do not operate that way, there is no way to tell without knowing a lot more about what the motor is doing.

Your other choices, if you can otherwise live with the higher speed, are to 1) increase the voltage to 264V using what's called a "buck boost transformer", 2) buy a new motor designed for 60Hz operation, or 3) look for other mechanical ways of reducing the load by at least 20%. For example if the load IS a centrifugal pump or fan, simply restricting the flow to what it was supposed to be will be actually be sufficient to reduce the load. The end goal can be simply measured by looking at the current going to the motor. If it is under the Full Load Current (Amps) shown on the nameplate, you are fine.

If you cannot live with the increased speed, then your only choice is to replace that motor with a 3 phase version and get a VFD.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[petronila]

Hi airwin,

Another alternatives are send the motor to workshop in order to rewind it (redesign for 60 Hz) in this case one important consideration is if the motor has or not centrifugal switch, note that if the motor will run at high speed then the centrifugal switch could not work proper and the starting winding can´t be disconnected so will smokes up.The work shop most consider include the centrifucal switch replacement by some electronic key or adapt a 60 Hz centrifugal switch, so this alternative could be spencive.

Taking account that you are saying that the motor is not continous rated another alternative could be use a three phase motor (1.3 times single phase power ouput) and run like single phase with steinmetz connection.


Regards

Carlos

 

[airwin27]

Thank you for your replies and i would like to apologize for some short information i have not added. the machine is an automatic slicer intended for slicing ham..something like this:

http://www.pacificfoodmachinery.com...meat-cheese-ham/ss-350a-automatic-slicer.html

is there any possible cause why that incident happened..take note that the machine is brand new.
Thank you.

 

[jraef]

Not knowing the exact details on the type of motor, it's most likely a simple Capacitor Start/Capacitor Run (CSCR) or maybe a Permenent Split Capacitor (PSC) type and the problem is going to be the the V/F ratio issue causing the motor to run hot to do the intended work. Then like Keith said, it has an internal protective switch that heats up faster than the winding damage happens and disconnects the power to the windings in the motor to prevent them from catching on fire. Repeated use like that will lead to failure in short order.

So you need to take one of the suggested actions: boost the voltage, replace the motor, or have it rewound. Rewinding a motor that small will likely be the most expensive option, but if the motor mounting is special, may be necessary because a commercial off the shelf motor made for 60Hz may not fit.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[Compositepro]

The slicing blade is turning 20% faster, the blade is being fed into the meat 20% faster than designed, and the volts/Hertz is lower than designed, so it is very likely that the motor is over loading. A variable frequency drive(vfd) set at 50 Hz would give the motor what it was designed for. A vfd will only work for certain types of single phase motors. It will not if the motor has a centrifugal start switch. I doubt that a meat slicer would use a start switch since it does not need a high start torque.

Rewinding will not fix the over-speed issue.

 

[airwin27]

Hello everybody, your replies are very appreciated.
Now may I know if a 50Hz machine with a single phase motor and 240V will be able to run continuously for production?
Please see the link below:

http://www.pacificfoodmachinery.com...meat-cheese-ham/ss-350a-automatic-slicer.html

With this kind of specifications, is this recommended for plant operation, I mean for production use with an 8-hour operation?

 

[waross]

Rewinding won't address the overspeed issue. The machine is probably rated for a sync speed of 1500 RPM. Rewinding for 60 Hz will give a sync speed of 1800 RPM.
An auto transformer to boost the voltage up to 265 Volts will preserve the Volts/Hertz ratio and get the maximum torque. If there is some surplus torque then it may be able to drive the load at 1800 RPM.
Another option is to locate a 50 Hz UPS adequate to run the motor and feed it with 220 Volts 60 Hz. If the UPS is not too sophisticated it may accept 60 Hz in and output 50 Hz.
I have just looked at the link that you posted. The machine is rated for 240 Volts, 50 Hz.
To run on 60 Hz the voltage should be 288 Volts.
Will it run continuously?
You will have to supply 288 Volts and try it.
240 Volts 60 Hz into a machine designed for 240 volts 50 Hz, will result in a torque of only 70% of normal torque.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[airwin27]

Happy New Year everybody!

Thank you for your replies. I would like to ask again if the machine has a design of:
415 Volts
50 Hz
3 Phase

Can it be used on an area with a source of:
440 Volts
60 HZ

If not, what actions should be made so the machine can perform well?

Thank you!

 

[waross]

Buy a VFD that is suitable for your supply voltage and frequency and suitable for the rated full load current of the motor.
Configure the motor as 415 Volts and 50 Hz or the exact nameplate values.
It should work perfectly.


Bill
--------------------
"Why not the best?"
Jimmy Carter