Efficiency of EM Ampli-Speed Magnetic Drives

[frohara]

I am looking for the efficiency of a 600 HP Magnitic Drive manufactured by Electric Machinery (EM), model Ampli-Speed. Does anyone know where I can find this information or has experience comparing this technology with other variable frequency drive types in terms of efficiency?

 

[jraef]

E-M is now part of a new company called ConverTeam.

In general, I've always known Magnetic Drives to be slightly less efficient than VFDs. This chart came from another Magnetic Drive mfr. It's probably pretty accurate although I'm struggling with understanding why the VFD would use more energy in the summer, maybe they are factoring increased cooling load on an indoor installation. Might be a valid point in some installations.

Their real claim to fame is that they say they are less expensive than VFDs, so if you are doing it for energy savings the payback is faster. But some of the literature I have read uses some fairly wild cost estimates for the VFDs. For example I read one where it said the Mag Drive would cost $44,00.00 and the VFD would cost $68,000! I don't know where they went shopping for a 200HP VFD that ended up costing $68,000, I think they were skewing the numbers just a tad...

As they say, there are lies, damned lies, and statistics. But when you really want a dose of untruthiness, look at marketing literature!



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[Skogsgurra]

What technology do they use? GTO? Magamps ?

Gunnar Englund

http://www.gke.org

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[jraef]

No GTOs or MagAmps, I perceive you might be thinking it's related to an amplidyne or Magnetic Amplifier because of the name, it is not.

It's actually more like an eddy current clutch drive than a VFD, but with even less electronics. To control speed they move a set of permanent magnets close to a plate or back it off and let it slip. Very little electronics at all and none of it involves the motor power. The only ones I've seen used in the field were on pulp refiners; high HP, no starting torque required.
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[Skogsgurra]

Thanks, Jeff. Yes, I was thinking transductor control.

Eddy current clutch? Not very efficient. Losses equal to speed difference times torque. Or are there some other tricks involved also?

Gunnar Englund

http://www.gke.org

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