Relay Coil Limitation

[DonsDaMan]

I never knew the reason for the shading coil! It was always on my "magic stuff you just accept" list until now.

I wonder what happened to our original poster?

 

[Terry Woods]

When I was in the Navy, we electricians were responsible for changing out motor bearings. We always found it convenient to lay the new bearing on a warm steam-pipe for a while before setting it on the rotor shaft. It would slip on with just a few taps - it worked great.

Sometime later, after I was out of the Navy and working as an electrician in an industrial environment I found that there were no steam-lines available for heating the bearings. However, there was this device that worked just as well...

I always find it interesting when someone finds a way to turn lemons into lemonade.

This particular device was a very poorly built transformer. The primary side (buried inside of the unit) was wound with copper wire. The secondary side (exposed) was composed of two parts... an upright "U" shape and a very loose fitting cross-bar that would close the "U" into an "O".

The laminations on the secondary side were few and poorly bound. And of course, the cross-bar was even more poorly bound to the main body.

This device is a "bearing-heater". The cross-bar is removed and the "U" is revealed. The bearing is set so that one of the uprights passes through the center of the bearing. The cross-bar is re-installed. The unit is turned on. After only a few minutes, the bearing is ready.

At some point in electrical history, someone made a very poor transformer. They knew it was poor because it provided low power at the secondary and besides, the damned thing turned into a space-heater! They then set about trying to figure out how to make it better. They came to realize that there were these "eddy-current" thingees happenin'. They figured out that these eddy-current-thingees produced heat... a lot of heat. Power that was supposed to be delivered out the secondary was instead being lost in the form of heat. After many tries, they found ways to minimize those eddy-currents. They figured out that it was better to use many thin laminations than solid iron. Thus was born the modern transformer.

The events that led to the transformer were recorded.

At some point later, there was a call for a device that would produce heat... a lot of heat. Somebody remembered the events surrounding the development of the transformer... he remembered that original lemon.

He (whomever he was...) decided that the best solution in this case was once the worst solution for another case!

This device is designed to produce a great many eddy-currents in the secondary. This device is designed to become a small, local space-heater!

Ain't "Duality" interesting?

 

[Rod]

Shoot! We just used a Calrod unit under a stepped cone. How inelegant.

Heating those 36" ID roller bearings was a different animal - and you can't use a 'rosebud'

Rod (The CNC dude)