What is it - variable phase angle regulator

England runs on 50 Hz and your motor will have a long and prosperous life @60 Hz, It will normally run 20% faster and produce only a little more vacuum. Probably your black box makes it run somewhat slower. For a quick fit you could use a variac, direct to the motor or a different speed controller. Yours seems to have died, normally shortening the triac and bringing the whole load to the motor that asks more current and hopefully tripped the breakers on time. Also clean your filters on time or when there are none, clean the house. See if it runs with a lower voltage to test - without load - say 110 or 120. If it has a field capacitor SUSPECT it badly too... if not starting.

This machine was built in Canada which is also 60 Hz, so I don't think it was because of that. I do think you are onto it when you say speed control. I finally surmised that must be what it is for. Vary the angle of one leg and the phase to phase voltage will fall.

They have run this machine 8 hours per day, 5 days per week for 14 years, so I want to have it running on Monday. Think I can wire around this and run the motors pedal to the metal? The operators had the control set to nearly 100% already.

By the way - I looked at the "turbines" and they are indeed a motor - a cheap open frame motor, but a motor.

I am not fully with you with the "legs".

Is your motor single phase or 3 phase?

Does it have a condenser somewhere? Is your pedal a mechanical thing that turns the poles?

I have seen industrial sewing machines that had that kind of speed control.

I need more info from you to understand your problem. What is on the nameplate of the motor?

What are the colors of the wires that come out of the motor. Probably the motor and your black box are both from the UK. The turbines I know of run continuously and a valve is opened when vacuum is needed.

"Variable Phase Angle regulator" says it all:

The Triac inside the "Black Box" is triggered to drive (conduct) at a variable point on the phase angle of the supply voltage. This is done via the variable resistor on the unit. By reducing or increasing the angle at which the triac conducts, you are varying the voltage and conduction time (==> total power supplied) during the AC Cycle (Sinusoid). The motor torque is the main item that varies and therefore, for the type of load here, the speed of the motor.

Very good, that far we are also. That is what triacs are used for. A simple single phase dimmer does exactly the same. And what about the legs? You have a solution? What motor is it? That box is probably that black because it only contains 5 components. I'd like to know what triac circuit I can supply him with, the Variac idea works also. And the speed he probably can control with a few capacitors too. IF HE TELLS WHAT THE MOTOR IS... anyway thanks for posting.

Sorry for the delay and thank you for you reply - I am out of touch with the whole world for the weekend - I am throwing a curve ball at you, using Americanisms. Legs are phases in the colonies, and a black box is an unknown device. We actually use these terms in our EE classes, but never think that the rest of the world probably doesn't. The pedal is as in the trucker term - "pedal to the metal" - full speed. Ten four? By the way, the device is actually housed in a black colored box.

An explanation of the motor wiring. Here in the states, we like life a bit more than you do over the pond. We have 120VAC to ground and 240VAC phase (leg) to phase (leg). So what you would run with a phase and neutral we run with two phases. This allows the voltage on our convenience receptacles to be a mere 120VAC to ground, not 240VAC. Thus I was able to survive my little experiment at 20 months of age where I stuck a fork into a receptacle. Had I been in jolly old England, this would not be happening now.

The triac solution is it - modify the phase angle in one phase versus the other connected leg, and the phase to phase voltage varies with it. Equal angle and zero voltage. Shift to 120 degrees and full voltage. I also arrived at this solution about 5 hours after my original post. The device is a "light dimmer" in one leg.

Now, how about the idea of eliminating the device, and running full phase angle all the time? (pedal to the metal) Anyone see a problem with that?

Most likely your "turbine" motors are what are called Shaded Pole motors; they can be controlled via voltage control, so your "black box" makes sense. It is, as you surmised, just a "dimmer" control. The pot is causing a delayed firing angle of the triac, which reduces the RMS voltage getting to the motor. Motor torque will drop by the square of the voltage change, so although you are not directly controlling the speed, you are controlling the torque and THAT is having the indirect effect of allowing the motor to run at a lower speed. If it had internal fusing it can probably be replaced, but most likely it did not, it probably had a "fuse wire" which is a little piece of wire designed to melt. like a fuse does, at a predetermined current level. Once that melts, it's not typically repairable. But a dimmer switch will work fine it you want to replace it, just check the motor wattage and ensure that the dimmer you select is rated sufficiently to handle it, allow some fudge factor in there as well.

Running it at full tilt boogie (another colloquialism to confuse the non-Americans ) will not harm the motor, but it will mean you will not have control over the amount of vacuum, with whatever consequences that bears.

"full tilt boogie" - I thought about using this term, but among the various uses of it, some are rather sinister on the western side of the pond. Didn't want to freak anyone out.

Fortunately, I discovered, whilest manually tripping the controlling contactor and adjusting the potentiometer, that the potentiometer in the black box has a switch to by pass it when set to 100%. I heard a nice click, and suddenly it sounded like Saturday mornings. You know, when the wife starts after the dust bunnies under the bed with the Electrolux. So, yes, we are running full speed ahead and vacuum wrapping products very nicely.

Thank you for the torque explanation - I hadn't thought of that.