Assuming that the voltage will be the same, the motor will run at 5/6 speed. So for instance instead of 1725rpm, it will run at 1437rpm. This may also afect the cooling of the motor, and it will tend to run hotter, eventually shortening it's useful life. It will also put out 6/5 more torque which may cause mechanical problems in some applications. So instead of 30 ft-lbs at 1725rpm, it will put out 36 ft-lbs at 1437rpm.
"Venditori de oleum-vipera non vigere excordis populi"
Cross posting is not a good idea. Try to post only in one forum and then if you dont get the response you want, then post in another forum. It saves confusion and aids a productive discussion.
There are many posts that have addressed this, try using eng-tips search feature.
Assuming we discuss an ordinary AC induction motor:
1) Yes, the motor will run at 5/6 speed.
Provided the supply voltage is also 5/6 of the nominal voltage for the motor, this is appropriate. (As correctly stated by Skogsgurra).
But:
2) A normal AC motor will put out as much torque as the driven machine requires, until it stalls.
This will in many applications be OK, but expect only 5/6 power output from the machine. The current uptake and heat generation will also remain what it was at 60Hz. It might run a little hotter, due to the reduced capacity of the fan.
3) There is no direct dependency between variation in reactive power uptake and variation in frequency. If you look at the equivalent diagram for the motor, the L (inductances) should remain constant, so the reactances should be proportional to the frequency.
This is all for now, as I'll try to keep it short.
Did you really read and understand the quesetion and answers given by me and jraef?
The higher torque (mentioned by jraef) is a real problem since it will shorten life of (possibly break) couplings and gear during start. It is true that the load torque is dependent on load - but that is not even necessary to mention here.
And, yes, the reactive power consumption will increase if you go from 60 Hz to 50 Hz without adjusting the voltage. mehteh asks for things to watch for when changing from 60 to 50 Hz. And this is one of them. I think you should consider what happens when the reactance is decreased - which is what happens when you decrease frequency.
