Synchronising ac motorsp

[gooseygumdrops]

Can anyone help me achieve the following. I have 2 motors driving 2 separate turn tables I wish these turntables to rotate at the same speed as the other and complete their revolutions in time. Both turn tables have different loading and may want to run quicker or slower than the other. Imagine 2 clocks I need the minute hand to constantly be pointing to the same number on each clock. So the main turn table speeds up slightly due to weight or motion I would want the other to speed up to match and the same for slowing. Any suggestions?

 

[roydm]

Synchronous motors

 

[davidbeach]

Vector drive VFD. If close is good enough, you might be able to get by with a sensorless vector drive. But through in a good encoder you ought to be able get extremely close.

Synchronous motors are theoretically a good option, but small synchronous motors can be very expensive compared to an induction motor and a drive.

But event better, is there any possibility of mechanically coupling them?

 

[Compositepro]

This used to be done mechanically with gears. Electric motor controls have been continuously improving for the last hundred years to be able to do the same thing. Thus this is sometimes called "electronic gearing" (do a Google search). There are quite a number of different motor technologies that can be used, and sometimes it is just a matter of personal choice as to which to use.

Since you already have the motors and turntables, that will determine the type of controllers you need. You have not said what type of motors you have. Things to consider are:
What level of positional precision is required?
How do you achieve or maintain synch at power-up and power-down?
What is your budget?

If you provide more details someone will give some useful advice.

 

[GroovyGuy]

what size of motor are talking about here? 2hp or 2000hp? Need the info....
I tend to agree with DavidB, a vector drive type of VFD would be my first choice.

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[waross]

In the days of transition from 25 Hz power to 60 Hz power a similar problem sometimes arose.
Some large plants chose to keep some 25 Hz equipment in service after the conversion to 60 Hz supply.
A 60 Hz synchronous motor could be used to drive a 25 Hz alternator through a suitable reduction gearbox. (12:5 ratio).
However one plant did not have surplus synchronous machines large enough to power a 25 Hz induction furnace.
The solution was to run two motor-generator sets in parallel.
The synchronous motors inherently run at exactly the same speed.
However in a multi-pole machine the machines may not be driven at exactly the same angular position.
For example with one machine at 12 o-clock the other machine may synchronize at 12 o-clock or at 6 o-clock.
For parallel connection of the 25 Hz machines both driving machines must synchronize at 12 o-clock.
A synchro-scope on the 25 Hz outputs will indicate proper angular alignment.
If the synchro-scope indicates 6 o-clock or some indication other than 12 o-clock the power to the motor running ahead may be momentarily interupted to allow pole slip until the proper alignment is indicated.
The motors will then remain in sync without further attention.
A small PMG generator may be attached to each motor so determine the position indication to send to the synchro-scope.
The PMGs should have the same number of poles as the main motors.

Bill
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"Why not the best?"
Jimmy Carter