415v star delta motor how to time
415v star delta motor how to time
(OP)
I have recently been asked if a 415v star delta motor that drives part of an extraxtion unit can be timed to operate for 5 minutes every hour. If this is possible can anyone please advise. I would have thought that this kind of timing to such a motor may cause more wear to it. I believe under normal circumstances this motor would have been running throughout most of the day. I believe that the motor in question is supplied by three phase and earth.





RE: 415v star delta motor how to time
RE: 415v star delta motor how to time
Check: a) The starting time is less than 3 seconds.
b) The current does not exceed the nameplate.
If so, your motor could work the proposed cyclic load without problem. Verify the steady temperature of the windings after 12 to 20 hours of work; it should not exceed the insulation class limits.
RE: 415v star delta motor how to time
RE: 415v star delta motor how to time
RE: 415v star delta motor how to time
The motor works 5 min every hour and starts wye, runs delta. The starting current is reduced to 1/3 of full voltage inrush and the mechanical stress is reduced proportional to I^2. See original post.
RE: 415v star delta motor how to time
http://www.sea.siemens.com/motorsbu/product/White%20Papers/Selection%20of%20Copper%20vs.%20Aluminum%20Rotors%20for%20Induction%20Motors.pdf
for 5000 motor starts limit
However, there are motors that exceed this number, e.g. fan motors that are frequently switched by a toggle switch.
RE: 415v star delta motor how to time
RE: 415v star delta motor how to time
on the other hand, have you thought about adding a VSD?
RE: 415v star delta motor how to time
RE: 415v star delta motor how to time
One start per hour would not be of concern for most motors provided that the starting time was within allowable limits for that particular motor. i.e. if the motor was designed to be used with a very low inertia load, and you started a high inertia load with it, you would expect to have a premature rotor failue.
Thermally, provided that the laod inertia was within the limits for that motor, there should be sufficient cool down period (as I read it 55 minutes) for the motor temperature to remain well below the rated temperature of the insulation.
Best regards,
Mark Empson
http://www.lmphotonics.com