Re: Stepper Drivers

"Harrison, Doug" wrote:

> From: "Harrison, Doug" <dharrison@...>
>
>
> > Sometimes it gets tempting to just buy IRF640's rated for 200 volts
> > and simply rectify the line...
> >
> > Chris
> >
> Depending on what kind of isolation your amps have, this might
> work
> fine. I read of one manufacturer that does this.

I would suspect that no manufacturer gets away with this anymore in
industrial equipment,
due to OSHA and NFPA (electrical code) requirements. This is just
too dangerous. It means that any part of your circuit is potentially
'live', and can't be touched, probed by line-powered instruments,
etc. I certainly wouldn't have such a design in anything I will use
or service. But, especially since the motor is likely to be mounted
on a moving part of the machine, and connected by cables, it is just
too likely that a cable could get cut or pinched, and blammo!
If the machine was well grounded, it might not cause any personal
injury, but the motor driver and other equipment, like the computer,
would get blasted.

Now, of course, this is how the 3-phase variable speed drives
work, but when you are driving 230 Volt motors, you at least
know there are hazardous voltages there.

Jon