electric motor speed change 1

[monfils]

We are looking to vary speeds of 3 electric motors (400hp, 150hp, 150hp), without having to change pulleys. Motors are for running crushing mills where speed needs to be adapted to material being processed. Cost is an issue.

 

[itsmoked]

You seem to have nixed the mechanical transmission method. Sounds like a VFD application.

While I'd probably look at some sort of mechanical transmission since you likely only need a relatively small variable speed region, VFDs have probably crossed below the price of 450HP transmissions by now.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

What kind of crusher? Some will work with varying the speed, some will not; you cannot assume it will unless you have already tried it.

Generally though, VFDs are the likely choice. "Cost is an issue" is a relative concept. What kind of cost are you looking to maintain? VFDs are not inexpensive compared to full speed, but compared to other methods of continuously varying the speed, they are.

Your choices are (in my opinion): Mechanical Vari-Drive, CVT (Continuously Variable Transmission), Eddy Current Drive, Magnetic Drive, Wound Rotor Induction Motor (if you can find one), or fluid clutch. I would stay away from DC drives and motors in a crusher application, too much maintenance. Of those choices, a fluid clutch would probably be the cheapest up front, but not exactly easy to implement and energy inefficient. A Mechanical VariDrive is a maintenance nightmare on a crusher and the most inefficient choice. A CVT is very expensive and large, ECDs and Mag Drives are inefficient and WRIMs, while a favorite amongst us motor heads, are somewhat complex for the uninitiated, require rare motors and now custom control systems. A VFD can use a standard motor (rated for VFD use if at all possible) and they are so common now that there are lots of resources available to maintain and troubleshoot them.


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[ozmosis]

monfils
Are you looking at varying the crushers or the feed to the crushers? it sounds like you might need to slow/speed up the feed rather than the actual crushers themselves.

 

[waross]

Is this for crushers, rod mills, ball mills, autogenous mills or something else?

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

 

[monfils]

All 3 crushers are Hazemag horizontal impactors, a primary and two secondary.
We crush aggregate for the concrete industry. Our sand has too much 4/8 mesh retained fine gravel and not enough finer sand. The only variable we currently can't alter to resolve this is rotor speed.

 

[DickDV]

Sounds like a VFD for each motor. I would caution you to size the VFD's to cover the peak amps that the motors will require to develop peak torque.

This may well require a drive a size or two larger than the hp designations would indicate. Bottom line: size by continuous and peak amps, not hp.