Sorry, I don’t know any thing about your motor run device, you appear to be knowledable on matters electrical, but before removing the exist capacitor do ensure they are fully discharged. This can be done by short circuiting each capacitor terminals with an old screw driver, I hope I’m not telling grandma how to suck eggs. As you have already bought the new capacitors and haven’t disturbed any of the wiring why not fit them and see if the converter then works as before. I think the transformer is wired as an auto transformer, non isolating. Converters are now a thing of the past, inverters have taken over, so might be worth while altering the motor connections to Delta and fitting an inverter.

This information could be way out of date

… I think MapQuest just scrapes stuff from available databases …

But anyway:

https://www.mapquest.com/gb/england/motorun-phase-converters-506536552

MichaelG.

How very strange, Trevor … I will need coffee before pursuing that any further.

A couple of notes to keep things going:

1. I have so far found no reference to Motorun on Companies House, so it may be a “trading-as” name.
2. a search for the VAT number on your invoice also drew a blank

For general interest … this one looks nice & clean and bears a very legible label:

https://gandmtools.co.uk/product/motorun-4-h-p-phase-converter-80216092/

C’mon chaps … “The Chase is On”

MichaelG.

Hopefully, a gallon of the brown stuff will quench the hypotheses.

If my memory is still working, about thirty years ago I did a detour on the way to Southampton to collect my MRPC from said address. The operation was a “Cottage Industry”type business run by a couple of guys rather than a white hot development. Access was via a yard in front of either (now misty) a wooden or brick building. I remember the yard in front, as when loading box into car, a cacophony over head was the mid day Concord(e) winging it way to wherever. It was purchased to run, and still does, me 3 phase V10.

Regards  Ian.

For the purpose of getting it to work, there’s a good chance getting two capacitors the wrong way round isn’t a problem.  Short answer is in bold below, the following explanation can be ignored by anyone with TL;DR!

The reason is static converters are imperfect even when set up optimally.  True 3-phase power consists of 3 lines each alternating 120° out of phase with each other.  Static converters use single-phase L and N to produce a 3-phase system in which two phases are 180° apart, and then create a third phase about 90° from L/N by adding capacitors.   A capacitor only circuit gives 0°, 180°, and about 270° rather than 0°, 120°, 240°.   The ‘about 270°’ is improved somewhat by adding an auto-transformer.

In electronics, the time taken by AC to pass through a capacitor by charging and discharging it, is equivalent to a -90° phase shift.  An inductor adds a +90° phase shift.  Approximately!  Both depend on the frequency and the impedance of the load.  Impedance is a complex mix of inductance, capacitance and resistance and in a motor, inductance varies with current drawn.   Start current is usually much bigger than Run current, and Run current varies with the load.  It’s impossible for a static converter circuit to get this right automatically so they come with a bunch of switches typically labelled START, LOW and HIGH HP.  These allow the owner to find the combination of capacitors that start and run his motor.  He has to experiment.  If Trevor gets C1 and C3 the wrong way round, all that will happen is the HIGH, LOW switches will be set differently for motor best running.   A guess:  C1 (6uF) is connected to the LOW switch, and C3 (10uF) to the HIGH switch.

As static converters are a bit of a bodge, no surprise that not all motors work with them!   Or that the power output and smoothness of the motor are both somewhat inferior compared with accurate 3-phase.

Rotary converters do better by putting an idler motor in the circuit.   The idler motor responds to the current drawn by the working motor, so the false phase doesn’t jump about so much.   Better technical answer, but noisy, physically bigger, more expensive, and relatively inefficient.  They do support having a number of different machines plugged into them, which is important in some workshops.

These days Variable Frequency Drives are usually preferred for fixed installations.   Unlike static and rotary converters, VFDs output correctly phased 0°, 120°, 240° power.  Quietly and with high efficiency. Plus speed control and a long, long list of other goodies.   Disadvantages include: understanding the manual, not plug-and-play; affordable units only support one motor, no sharing;  EMC issues; and a spiky synthesised waveform likely to poke holes through the insulation of an electric motor made before 1970.

In the UK at least, Electricity suppliers are extremely reluctant to provide 3-phase to domestic users.  I guess this is partly economics – small users are unprofitable!  In the past single-phase installation costs were partly amortised over a 40 to 50 year supply life, usually in a scheme doing a whole village or new housing estate.   In contrast today, singleton domestic customers seem be quoted the full initial installation cost.   Not too bad if a 3-phase connection point is adjacent, but horrifyingly expensive if a deep trench is dug across a busy main road, poles put up, or. god forbid, a new transformer is needed.   Counter-intuitively, the per customer cost of converting a whole street to 3-phase is cheaper than running 3-phase to one small workshop; it’s because the installation expense is shared by many customers.   Electric cars may be the best bet for getting Model Engineering 3-phase. With luck, the government will encourage us to install 3-phase chargers en-mass by running an efficient roll-out scheme, where they carry the initial cost.   Unlike a small workshop using tiny quantities of 3-phase, car chargers will pay for themselves by being used!   And once 3-phase is on the premises for a car charger, then running a cable to the workshop will be much cheaper.

Dave

I don’t know if this will be of any help to anyone, but as I stumbled across it:

https://www.electro-tech-online.com/threads/3-phase-converter-schematic-miller-system.100563/

MichaelG.

Machine Mart sell Clarke branded static converters – the manual for their 2 hp version is here

The manual includes a circuit diiagram & a parts list that details the capacitors used.

I have one to drive a small Ingar manual surface grinder, though it would also run a 3 phase version of an RF30 mill-drill (now departed). Seems to work OK, though the current price of nearly £350 is way more than I paid for mine (around £200 on one of their “Vat free” promotions IIRC). At the current price it may now be more cost effective to swap the existing motor, which is 415v only, than buy the static converter.

Nigel B.

I seem to remember that Transwave statics have some sort of voltage sensitive boost device in them and I think it was on here that it cropped up as a fault. They are I seem to recall commercially available off the shelf ? This sort of got round the need for the start switch, only needing to match the run caps to the motor.

If the OPs problem IS a faulty cap a Good meter will give a clue as to this. I hope the caps are right voltage,400V+ and type ? Good Luck. Noel.