Motor Specification

[timjturner]

Hello,

I am writing my first motor specification and I'm unfamiliar with some terms.

I'm looking at an example that specs a 10:1 minimum speed range. What does this mean?

I need help determining insulation class. Anybody willing to provide or know of any sources on the internet for help on this issue? The example I have shows Class F Minimum, inverter rated per NEMA MG1.

Thanks!

 

[Skogsgurra]

A few very basic guidelines (mostly for EU) is given here:

http://www.bevi.dk/specifications/writespec.htm

More complex answers are given on AB, ABB, Baldor, Siemens etc home-pages.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

You should specify where you are in the world. Motor specs for North America are different than for the IEC countries. If you are in N. America, see if you can get your hands on a copy of NEMA MG-1, the basic design criteria for motors used here. If not, you can get snippets of it from internet sources. Here's a decent resource, it's not written as a specification guide but may have information to answer your questions: EASA handbook from Joliet Equipment


10:1 speed range by the way means that the motor is designed to be used with a VFD, and you can "safely" run the speed at 1/10th the rated speed without worrying about cooling, accuracy, loss of torque etc. So if you have an 1800RPM motor, you can run it at 180RPM without external cooling; theoretically anyway. Regular motors are typically only good down to 5:1 or maybe 6:1.

 

[sreid]

Class F insulation allows a maximum wire hot spot temperature of 155 deg C. 10:1 speed range and inverter duty kind of go hand in hand.

10:1 Motor will not overheat at low speeds.

Inverter Duty Insulation rated for Drive switching spikes

NEMA MG1 can be downloaded at the NEMA website.

 

[dpc]

NEMA MG1 can be downloaded at the NEMA website.

The last time I checked, only a condensed version was available on-line. Has that changed?

 

[timjturner]

Thanks for the help. I am in North America. I'm still attempting to get my hands on NEMA MG1. The IT department at our company has conveniently blocked nema.org. Unreal!

 

[dpc]

http://www.nema.org/stds/mg1condensed.cfm

This will take you to a free download of a condensed and out-of-date version of MG-1. The current 2006 version costs $239.

 

[jraef]

A lot of corporate IT departments routinely block access to all .org sites, assuming that they are not going to be work related. You should be able to ask to be allowed to access it. I can, and it usually only takes 4 or 5 days for that to transpire!