7.5HP Three Phase Motor Conversion

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Senior Member

Joined: 17/04/2008
Location: Canada
Posts: 196
Posted: 05:15am 28 Sep 2008      

Good question Gordon.

True, there's not much need to cool the rotor. The stator may benefit from the extra airflow, though.

My main reason for keeping the fins on is that they keep the rotor laminations together. That last time I turned a rotor down (for someone else's project), once the rotor had been turned down so far that the fins were cut off, the individual laminate disks started to spread apart. The person I was doing this for decided to bolt them back together through a set of lightening holes that were available. This rotor here doesn't have any lightening holes, so if the laminations started to separate, that would be the end of it - I would end up removing them all and making a new big cylinder to replace them. Admittedly that would give a better return path for magnetic flux... but lots of pain for little gain, really.

So it's actually a structural reason, more than anything else.

I won't take you up on the 720 RPM motor: I already have one and it weighs twice as much as this 4-pole motor!
Steven T. Fahey