Hi Guys,
Here's one for you.
A mate of mine that works as a Maintainence tech in a factory that prints newspapers, related this story to me recently and I must admit, it has me stumped.
OK,
There are a set of machines that they use to roll plastic film over the papers (to prevent them from getting wet after they sit on your lawn after being delivered).
The machine uses a set of rollers and various other mechanisms, to roll the paper and wrap the film over it.
The machines are driven by a 230V 50Hz 1 HP single phase , cap start Cage induction motor and this in turn feeds a set of chains and sprockets to effect the rolling, etc.
Now, here is the crux of the problem, the motor, when started up for each roll, drives the chains at the full speed of the motor and is geared down to suit the rolling machine.
However, they have noticed that every now and then, the motor will accelerate to speeds beyond what the motor is ought to (or even designed to) run at.
How on earth is this even remotely possible?. [Linked Image]
I was under the impression, that the speed of an induction motor was controlled by the supply frequency.
BTW, this motor has no speed controller or governer on it to reduce the operating speed under normal operation.
It's the first time I've ever heard of such a thing.
Can anyone help at all?.
Thanks,
Mike.
[Linked Image]


[This message has been edited by Trumpy (edited 08-19-2006).]