Hi all,

Soon I should have most of the components necessary to build my phase
convertor. I'd like to do a few trial runs in which I wire the
components together and test the convertor's performance before I go to
the time and expense of building a metal chassis to mount it on.

So today I was wondering how I could create a variable load in the range
0.5 to 2 hp. Has anyone done this before? The only three phase workshop
machine I have is a power hacksaw with a 1 3/4 hp motor. This runs
through a static phase convertor I built and I don't really want to
disturb the wiring if I can avoid it.

Ideas I had are as follows, with some disadvantages listed:

Motor bolted to wooden board. Insert 2" x 4" under pulley and lever
upwards to create load. Load control is a bit crude, as is the whole
setup, but I've used it before and it works after a fashion. Sets fire
to wood, too.

Motor bolted to board with slightly more sophisticated homebrew braking
system, possibly allowing weights to be loaded onto a lever. Still
crude, but a bit more controllable.

Motor driving variable pitch propeller in small tank of liquid. Neat,
but I don't know where to get a variable pitch propeller for little
money, or how to match it to the motor.

Bolt car brake disc/drum to motor pulley. Use hydraulic calipers to
apply load. Could be quite neat, but it would be a faff to build because
of needing a reservoir, flaring pipes etc. I'm also not sure how to
regulate the pressure. Plus car parts dealers in our area charge big $$$
for car parts.

I rather like my final idea. A while back a friend offered my a
hydraulic pump from a concrete crusher (i.e., a test rig for measuring
compressive strength). I think it has a 2 hp three phase motor and is
the kind where the motor is mounted vertically on top of the pump, with
the pump hanging down into the reservoir. So I thought I could cut a 47
kg propane cylinder in half, make a plate to cover the opening and mount
the motor/pump unit on top. Then I could have the oil circulating
through a needle valve which regulates the load. Plus I'd need a
pressure relief valve, contactor etc. It sounds like a neat idea but I'm
unsure how much the hydraulic bits would cost.

Any thoughts? Has anyone done this before? I don't want to spend too
long on this, because I want to put my effort into the phase convertor,
but it would be nice to have a controllable load.

Best wishes,

Chris