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Bob Fisher
06-19-2012, 03:41 PM
There is a rather large transformer like thing in series with the hot AC line input to this speed control. It is wound with very heavy copper wire. What purpose does it serve? Should have taken more electrical courses in college. Bob.

MaxHeadRoom
06-19-2012, 04:06 PM
It could be a toroidal transformer if it is fairly large, also in many cases a suppression device is fitted, again it often is a toroidal device, describe the size and if it looks like it has a donut core with just a few turns?
http://www.murata.com/products/emc/knowhow/pdf/26to30.pdf
Max.

deltap
06-19-2012, 04:54 PM
I think you describe a line reactor. It is more like half of a transformer. Used to reduce noise. More common between motor and drive. Then it's called a load reactor.

The Artful Bodger
06-19-2012, 05:09 PM
An inductance or choke, it resists changes in current. It is more effective at hight frequencies and may have minimal effect at 60Hz. It purpose is probably to stop sudden switching 'noise' getting back onto the mains and into your TV.

Bob Fisher
06-19-2012, 05:41 PM
I would take it that for my use, it is not necessary. I'm still trying to determine the resistance of the bad resistor, color code stripes do not make sense to me.Best measurement I could get says 292K, but colors don't matchi. It is difficult to determine the colors. It is a Proform TM and the resistor is R37. Maybe someone has one and can verify. Thanks, Bob.

MaxHeadRoom
06-19-2012, 06:22 PM
You mentioned 'Broken' resistor, if so this will be difficult to measure, if it is a precision value, there is another digit before the multiplier.
What are the colours? if you can make them out?
If it is not burnt, but just broken then there may be a chance of coming up with the value?
Max.

Bob Fisher
06-19-2012, 07:56 PM
Max, near as I can tell, the colors are :brown(maybe red) ,orange,yellow,white, and another brown/red. My measured value is 293Kohms .Difficult to measure since the lead is broken right at the resistor.Thanks for looking, Bob.

mixdenny
06-19-2012, 10:11 PM
There is a rather large transformer like thing in series with the hot AC line input to this speed control. It is wound with very heavy copper wire. What purpose does it serve? Should have taken more electrical courses in college. Bob.

It's a choke. In the original use, it evens out the pulses caused by someone walking on the belt, which tends to make the motor speed up.

Dennis

kbertoson
06-19-2012, 10:30 PM
Bob, here is a link to a good article in "instructables". The poster also has links to various schematics for different model treadmills. i hope this will help you out. http://www.instructables.com/id/Use-a-Treadmill-DC-Drive-Motor-and-PWM-Speed-Contr/?ALLSTEPS

jkilroy
06-19-2012, 11:09 PM
I have a large (4ft dia) shop fan with a treadmill motor on it. The large choke you will want, without it the motor has a hell of a loud Hummmmmmm!

Mike Amick
06-20-2012, 02:10 AM
wow ... good tip .. I was wondering how to get rid of that hum I have
with some setups...

thanx

Forrest Addy
06-20-2012, 06:37 AM
The hum is magnetostrictive noise from alternating fields within the motor. Line chokes in an SCR and PWM flywheel the skarp spikes that make this hum particularly annoying. There is a complication of back EMF sensing the motor control uses for feedback. Beefy inductors may smother it. Close regulation isn't particularly important on a treadmill or a machine tool.

But wait there's more: RFI. Treadmills and equipment that switch power to control motors have to pass RFI standards. Adding chokes, capacitors, varistors etc snuffs out the line spikes before they have a chance to radiate radio frequency noise (also known as "static buzz" "hash" or "RFI").

Run hash generating equipment like VFD's, PWM and SCR DC drives with long unshielded conductors and all you have is a radio station that plays RFI over a wide range of frequencies making AM radio a symphony of static. Enclose the drive and control station, shield the conductors and signal wiring and place the RFI filters close as you can to the switching devices, and run a proper bonded ground and there's little left to radiate to the world and the top 40 radio station playing on the Zenith you inherited from Grandma.

So, you with home installed VFD's and DC drives better run your conductors and control wiring in conduit or BX and add RFI filters to the line conductors as they enter the metal enclosure (hint hint) you have your RFI emitting devices mounted in. It doesn't have to be verwhelming just adequate and properly implented.