05-25-2012, 05:28 PM
Scavenge a cooling fan from an old computer power supply or check out the fans at the local electronics repair place and attach it too the fan cover of the 3 phase motor. Hook up a DC 12V power supply to power it and then it will keep your motor cool.
Walter
Walter
(05-22-2012, 01:37 PM)Hopefuldave Wrote:Highpower Wrote:Yes, that is a good point John.
If you run the motor too slowly - for too long, they will overheat since the motor cooling fan blade slows down as well. Work on and off for short periods of time in order to let the motor cool down between times, or set up an additional external fan to help cool the motor as it runs.
They do make special inverter duty motors that have a separate motor and fan built in to handle that, but they are somewhat expensive.
Just use common sense and keep an eye on the motor temperature if you are using a standard TEFC motor.
Wot he said...
A lot of VFDs have configurable relay outputs - on my ABB inverter I have one configured as Normally Closed, opening when the VFD output frequency goes above 30Hz - that way it switches an external mains-powered fan *OFF* when the internal fan's running fast enough to cool the motor, back *on* when the motor speed drops (including when the motor's at rest or the VFD's powered off for a cool-off!) The fan at the moment is a cheap desk-fan-in-a-plastic-cage that cost 50 pence at a carboot sale hung on some sheet ally brackets, I'm hoping to find a way to fit something a bit more, er, industrial :)
A lot of the DC motors used in smaller lathes could benefit from a separate fan, too - often they get used at low speeds with heavy loads, a recipe for overheating!
Dave H. (the other one)
starlight_tools, proud to be a member of Metalworking Forum since Apr 2012.