VFD retrofit Hobbymat BFE65

**birchy** · 10-09-2013

Originally Posted by manofgresley

...to variable DC speed control...

I assume you meant AC control? If so, the mechanics are probably the hardest thing to do...in particular getting a motor small enough to fit the machine without giving up too many horses.

Regarding motors, the basics are that a 4-pole will run at approx 1425RPM at 50hz and a 2-pole will run at around 2850RPM at the same frequency. The big decision is whether to choose the slower 4-pole (for more torque at low speeds) or the higher top speed of the 2-pole but with reduced torque at low speeds. You can use stepped pulleys or gears to overcome this but I just didn't have the room for such niceties on my machine.

**EddyCurrent** · 10-09-2013

Maybe you could fit a DC motor with associated speed controller, think of a variable speed mains electric drill for example or even a lower voltage system.

**manofgresley** · 11-09-2013

Hi

Yes, that's what i was thinking of, DC motor control, do you know of any info i could look at ?

Regards

Ray

**EddyCurrent** · 11-09-2013

Sorry, I don't know why I didn't see that in your original post, I think the term VFD in the thread title immediately made me think of AC (which it is)

Fracmo | Brushless DC Motors, Fractional DC Motors, Gearbox Design & Electric DC Geared Motors

These look to be the part but no prices, I'm assuming it's something like 250Watts you need ?
They seem to be used in electric wheelchairs etc. so maybe a company who repairs them may have second hand units ?

also http://www.drivesystemsuk.co.uk/dc-m...earmotors.html

There are loads of DC controllers on ebay or Amazon at very low prices but obviously would need to be compatible with the motor and supply voltage.

**m_c** · 11-09-2013

DC is different.
For cheap motors, old treadmills seem to be the way to go, combined with a KBIC speed controller.

Unless you really are trying to do the conversion as cheap as possible, I wouldn't use anything other than a KBIC, as they're quite popular, reliable, and not that expensive to buy new. I run a KBIC in my little lathe, as it came with a DC set-up and a dead Cheetah drive, and a KBIC was the cheapest main stream option I could find at the time.