Motorun 2HP statin 3phase converter

[45chopParticipant @45chop]

Hi there,

Can anyone help me make the right power connections on my Elliott Omnimill.

The 3 phase output from the converter has 4 core & earth (Brown, Black, Grey, Blue & earth)

The Elliott Omnimill was connected with 3 core & earth (Brown, Black, Blue & earth)

I have no knowledge as to whether the converter is working correctly as I just purchased it from eBay untested. I plugged it in and took some readings with my multimeter, photos attached.

Hopefully someone here can advise me please.

Thanks, Stefan

[Clive FosterParticipant @clivefoster55965]

Stefan

Summary:- Just follow the colours.

PM me your E-Mail address and I’ll send you a PDF copy of the instruction sheet I got with mine many years ago. Seriously foxed but legible!

The immediately relevant paragraph says :-

——

Three Phase Output

The output of all converters is through the rubber 4 core cable,. phase colours are BLACK, BROWN, & BLUE, GREEN-YELLOW is EARTH.

On machines with  push-button contactor starters, the phase leads have to be connected as follows:-

Connect BLACK & BROWN phase so they feed the outer two terminals on your contactor, with the BLUE phase on the middle terminal. Often its not possible to see which wire goes to which terminal, then simply connect the phase into your input at random the press the starter. If the contactor buzzes and does not pull in or does nothing then change any of the phases and try again. If the contactor pulls in and the motor rotates in the wrong direction then reverse BLACK and BROWN phases.

———

Translating for mere mortals.

Assuming the innards haven’t been got at by the re-wiring bodger the BLACK & BROWN phases come direct from the transformer and will be at full nominal voltage. So these are the ones that should drive contactor for reliable operation. The BLUE phase is the generated “wild” leg so its voltage and exact phase cannot be relied upon. If that phase drives the contactor coils it may not operate properly.

In a static converter, with no integral motor, the BLUE phase (or its equivalent) doesn’t exist until the machine motor starts turning. The machine motor interacts with the various capacitors to generate the “wild” phase.

In a rotary converter the integrated motor generates the “wild” leg but its voltage and relative phase is not as reliable as the phases derived directly from the transformer. The integrated motor only has limited generation capacity. Frequently the high currents demanded on start up not only deplete the generated phase leg voltage but also shift the relative phase. This variation is often sufficient for the contractors to drop out. Especially if starting under load.

In general it’s not a good idea to start motors under load when using a converter, especially not with static ones which basically only run on two (and bit) phases during start up.

I added an external pony motor to my 4 Hp(?) Motorun static converter which made things work much better. Maybe 3 hp or 5 hp. After entry a quarter of a century memory has faded.

Clive

[noel shelleyParticipant @noelshelley55608]

IF you have 4 wires + earth then you MAY have 3 phases + neutral + earth. It is also possible that one wire is NOT connected. In the context of a static  converter to talk of 3 phases is not strickly true, but it works. Noel.

[45chopParticipant @45chop]

Thanks Clive and Noel, hopefully all will go well, famous last words.

[Clive FosterParticipant @clivefoster55965]

Noel

Fortunately the Motorun static converter doesn’t have a neutral connected to the star point so it’s just a matter of identifying the phases directly derived from the mains incoming voltage to make the control gear behave.

Quite robust really. Short circuiting the mains derived phases (BLACK & BROWN) together will let the magic smoke out tho’.

Clive

[45chopParticipant @45chop]

Hopefully the magic smoke can be avoided, here’s some photos of the vertical motor & the original connections in the control panel marked up A B & C

[BazyleParticipant @bazyle]

Hard to see in the picture of the motor. Is the brown wire going from B to N? It looks like the yellow earth wire is going to A and the Blue phase is on the chassis! Perhaps the previous owner was colour blind or suicidal.

[45chopParticipant @45chop]

[45chopParticipant @45chop]

I think this is star configuration

[Clive FosterParticipant @clivefoster55965]

EEEK!

Your motor connections are A, B, C for the three phases and N for the neutral, star point.

Maybe consider pulling new wires through the conduit in the current, post 2004 standard colours.

Pre 1977 flexible cables used red, yellow and blue for phases 1,2,3 respectively and black for the neutral, star point, connection. Earth was solid green.

Post 2004 flexible cables use brown, black, grey for phases 1,2,3 respectively with blue for the neutral, star point, connection. Earth is green and yellow.

These days if I were putting that converter into service I’d buy myself some 4 or 5 core cable in the correct modern colour codes and replace both the converter output cable and the machine wiring. By modern standards the old Motorun output cable colours are seriously confusing.

Having (finally) gotten out of the minimal change bodger habit my practice for the last 20 odd years has been to use 5 way commando plugs at each end of a modern colour code, steel braid re-enforced, flexible connecting cable. Internal machine wire is either old style 3 red for phases, black for neutral and green for earth or re-done in current colours.

Not a fan of loose boxes with a fixed cable to the machine.

Clive

[45chopParticipant @45chop]

Thanks Clive, So the Motorun I have is already correctly wired with Grey, Black, Brown, Blue and earth in a 5 way commando plug.

Grey is the ‘wild leg’, black and brown are the two phases and blue for the Neutral ?

Unfortunately I’m still confused as in, does it now matter in how the Grey, Black & Brown connect to A, B & C ?

[Clive FosterParticipant @clivefoster55965]

Objectively no because the motor input connections are effectively the same because each goes to one end of a motor winding and the other ends are connected together at the star point.

In practice I’d stick with the phase 1, 2 , 3 conventions and connect :-

Brown to A – as phase 1

Black to B  – as phase 2

Grey to C   – as phase 3

which should leave the motor running the correct way. Interchange any two phase wires if it runs backwards.

I have multiple machines so sticking with the convention removes one potential source of confusion if I need to do any electrical stuff. Not such an issue with only one machine.

Clive

 

[45chopParticipant @45chop]

Update, not quite there, powered up that I know of, as in the inverter clunks and hums but pushing the contact switch on the control panel doesn’t hold down

[45chopParticipant @45chop]

Another update, it is working now but the contact coil vibrates, occasionally holds and the motor runs but occasionally won’t hold, switching from overhead to horizontal motor sometimes starts it.

[45chopParticipant @45chop]

5 minutes running, is it too warm or normal 

[Clive FosterParticipant @clivefoster55965]

On a day like this that temperature isn’t too bad but things don’t sound really right.

Unfortunately I don’t have a circuit for the Motorun unit, or any other commercial one for that matter. Back when I was into such things I hovered up a lot of data from the internet of varying dubiousness but no clear fault finding guides.

When you say contactor buzzing presumably you mean the ones on the machine.?

Your Motorun unit is much newer than mine. Mine simply had big switch to turn it on, no contactor inside just as voltage sensing relay to disconnect the additional capacitor needed for start up.

If it has a contactor inside to do the on/off duties it should be completely reliable.

The relay or contactor used to control the start capacitor should tun on briefly as the motor runs up then release.

Machine contactor chattering is generally due to insufficient coil voltage. Verify voltage and make sure its operating coil goes directly to the mains fed phase, both when operated by the ON button and when running. As I understand things its best to hold the on button down until things come up to speed.

Not problem I ever had.

Lumpy running is due to phase voltage and angle imbalance. You need to find the best switch setting for the additional capacitors used to help create the “wild” leg. As I recall things the best switch setting on mine was rarely what the label and motor rating implied.

The DIY folk tend to advise simple experimentation.

Check the phase voltages supplied to the motor. You should be able to find a switch setting that makes them reasonably close. Never the same.

As I said mine annoyed me sufficiently that it got converted to a rotary style with a permanently connected motor. Much better behaved.

I’ll have look through my literature later tonight when the weather has cooled enough to restore normal brain functions to see if I’ve got anything useful. As I recall it the Transwave folk have some useful stuff on line. Unfortunately most of what comes up on search is American and they do it a bit differently.

Clive

[45chopParticipant @45chop]

We haven’t cleaned up the motor yet, maybe some of the grime is on the brushes and commutator causing excessive start up. I have adjusted the spring rate on the coil, when set on the low end it definitely will not start, however at the max end of the scale marked as 4amp it starts with the least chatter. The inverter definitely needs to be in start mode and definitely clicks in and out as it starts. I’ll also see if the inverter switch gear HP have any bearing on motor temperature

[SillyOldDufferModerator @sillyoldduffer]

Just a guess because I’m having difficulty relating the wiring in the photos to what I understand of 3-phase motors!   The plates suggest three 3-phase motors.   Two of them support star or delta connection, but the little one (coolant pump), may be star only.   Is it possible the mill is wired in Star, and is intended to run connected to a 440V supply?  At least one photo suggests star, but maybe it becomes delta behind the scenes.

If star, the static converter won’t provide enough oomph to reliably start and run the motors, because a static converter is typically limited to 240 across phases, and further disadvantaged because 2 phases are firmly locked at the wrong angle, whilst the third is faking it!  Although fiddling with the switches generally fools the motor into starting OK, the arrangement is far from perfect, and may not be ‘good enough’.   This is why folk spend the extra money on a pony motor, which does a better job of faking the 3rd phase, and why VFDs are so popular.  The 3 phases output by a VFD are much closer to the real thing than static or rotary converters.

Not much evidence of it, but another possibility is the electrics are set-up to start the motor in star and then and then switch to run in delta.  Unlikely, but that too would bemuse a static converter!

Is the multi-meter able to measure capacitance?   The capacitors used in static converters take a hammering and don’t last forever.  Not unlikely in a second-hand unit that one or more of them is no longer up to spec, in which case the converter may not be able to match to the motor(s).   Symptoms as listed by 45chop, including overheating.   Cure, identify and replace low-capacity capacitors.   If more than one is faulty in an ancient converter, probably wise to replace all of them.

Going back to the star/delta uncertainty, knowing how the mill was connected before purchase might help.   Wired industrially to 440 3-phase, or run from a static converter, or what?

If it were me, I’d trace the entire circuit, paying particular attention to the motor windings.   If they’re star wired, the fix is to reconnect in delta.

Dave

 

 

[45chopParticipant @45chop]

Hi Clive, buzzing/chattering from the control panel contacter coil. There appears to be a spring loaded adjustment, which when set at it’s loosest position (4amps) allows the motor to start with the least buzzing/chattering.

[Clive FosterParticipant @clivefoster55965]

Dave

The Motorun static converter has an autotransformer converting the 220 volts mains to 440 volts so that it can be used on star connected motors.

Mine worked fine except that I was never happy about the phase voltage imbalances.

 

45chop

That spring loaded knob is the overload setting. There is a bimetallic temperature sensitive switch device in the output power feeds. If the motor draws too much current the bimetallic switch heats up and breaks the coil circuit causing the contactor to release and turn the motor off before it gets damaged. Generally take a couple of seconds to react so the short term high start up current goes through OK.

As you have it wound up to maximum there is clearly far too much current going through on one, or more, phases during start up.

I’d try disconnecting the motor after the contactor and see if it operates OK on its own. This will confirm that the coil is correctly connected to the mains fed (via the auto transformer) phases.

My money is on the phase currents being seriously out of balance due to incorrect capacitor values.

Clive

[45chopParticipant @45chop]

Hi Clive,

Is there anyway of measuring those voltages ? When I measured the output on the plug, I got what seemed to me some odd readings but then, I really don’t know about 3 phase.

[Clive FosterParticipant @clivefoster55965]

Result, sort of.

The wild leg is way, way out of balance.

I notice from one of your earlier pictures that the wires from the contactor to motor are marked 1, 2, 3 which helps identify the phases

To recap :-

Brown is phase 1 which should align with wire numbered 1

Black is phase 2 which should align with wire numbered 2

Grey is phase 3 which should align with wire numbered 3

Blue is the neutral which your machine doesn’t use so shouldn’t be connected anywhere. Take it to the commando plug but nothing on socket.

In an earlier picture you have blue going to one contactor connection. So you have 2 phases and neutral on the contactor not 3 phases.

Replace the blue with the grey wire and all should be well.

When its running you should see around 200 to 240 volts between any pair of the phase wires ie :- brown, block , grey

Clive

[45chopParticipant @45chop]

Hi Clive,

Incredibly, I’ve managed to get the polar opposite of your suggestion ! The earlier photos with blue wire is as I purchased the machine and definitely hasn’t helped me in the slightest. I have terminated the neutral where it enters the control panel. I’ll try swapping out the order of the Brown, Black & Grey tomorrow, I’ll also reset the thermal cut out back down to 3 1/2. If I do find the voltage measurements across the coils to be wildly out of kilter,  what would the preferred course of action be ? I’ve read a little bit about 3 phase VFD, would that be likely to work or will I need to go down the route of a rotary inverter conversion ?

[noel shelleyParticipant @noelshelley55608]

Clive is right about the adjustable knob, it is the overload protection and should be set to the motor Full Load Amps as per the data plate on the motor. Neutral is not used in this application so leave unconnected. Brushes and Commutator ? I thought this was an induction motor ? Good Luck. Noel.

[45chopParticipant @45chop]

Did a little bit more work today, motor was filthy. Coolant pump impeller has rotted through and won’t lift the coolant more than  a foot. 

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