60 Hz Motors and 1750 rpm

What do you consider "in writing?"

This message is "in writing," and I'm going to tell you as a registered professional electrical engineer that 60 Hz motors run at 1450 rpm on 50 Hz power, and is indeed independent of horsepower or voltage. The reason for such is a function of number of magnetic (electromagnetic) poles in the motor and the power line frequency.

Variable frequency drives (VFD) can be used on 60 Hz motors to make them run on 50 Hz power at speeds greater than 1450 rpm.

Bill:

This idiot I am trying to satisfy wants to see something from a technical manual, that is the "in writing" I was referring to.

Thanks for your reply.

Ken

This is an excerpt from Freescale Semiconductor (formerly Motorola):

"AC Motors: Invented in the same era as the brush DC motor, the AC motor itself is divided into two major categories: asynchronous (induction) and synchronous. When driven by a fixed-frequency AC source with a constant load, the induction motor operates near the frequency of the input source (or multiple thereof), while the synchronous motor will operate at the input source frequency (or multiple thereof). As the frequency of the source is varied, both motor classes will accordingly change rotational speed. However, as the load changes, the difference between the input line frequency and the rotational speed of the rotor for the induction machine will be greater than that of the synchronous machine because of magnetic slip (the difference in rotor speed versus stator speed in a motor) caused by induction."

You can get more at http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02nQXG3MYxCKS2JjTF

Other excellent sites for motor theory are http://www.reliance.com/mtr/mtrthrmn.htm and http://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee2/bdeee2_1.aspx

Bill:

Thanks for your help. I am a Mechanical Engineer, so if you ever need any advice or help from my side of the pile, just let me know.

Ken

make sure that the motor is VFD rated, when you use a VFD with on it.

or install a gear box on the end of the motor to change the output speed.

Quite.

Yes, it's possible, i.e by inserting a VFD between power supply and motor.

Ask to VFD manufacturer such as Allen-Bradley (Rockwell), Siemen, Yaskawa, etc wether they have VFD with input frequency 50Hz, and output freq. max. 60Hz?

But you should consider the prices, which one is low cost, buy new VFD or Motor, it's depended on kW.

Then, you should think too, the effectiveness of that VFD. because VFD is a control unit which maintenance and trouble-shooting are required. If you will have trouble with VFD someday while you have no man who's capable in trouble-shooting, you will have new trouble to be solved then.

In short term, are you sure that you need VFD in your manufacturing line?

regards,