One phase into Three will go?

[nicholgd]

Hi I hope this post is in the right place.
 Can you run a three phase dimmer from a single phase supply ,with a current limiting circuit breaker?
 I'm the lighting man for our local drama group / village hall capacity 100. We have two 4 way dimmer packs , one 5A and one 10A. These run a motley collection of 8 frensels and Preludes plus some mismached led pars all controlled by a basic 18 channel desk.
We had our Panto last weekend. Dress rehersal lights working fine. Friday night I turned on the lights and there is no response from the second dimmer with two of its channels stuck half on . After getting over the panic attack and some frantic re plugging and repatching we manage to do one of our best Panto yet.
After the shows, swapping out DMX cables and connecting directly to the dimmer with a second desk proves the dimmer to be faulty.
This is where the plot thickens. I rescued some lighting bars and two twelve way dimmers from a local church that was being refurbished.  The dimmers are Electron model E 1612 ,but these are three phase and the village hall has only single phase supply.
On the Electron dimmer units the first phase supplies dimmer channels 1 and 2 , 7 and 8.The second phase 3 ,4 ,9,10 and the third  channels 5,6,11,12. So it would be awkward  to use the dimmer with only one phase connected.
The big question, is it Ok to common the mains inputs so all 12 dimmers will work , and limit total current draw via a circuit breaker/rcd? This would replace both existing 4 channel dimmer units.
In the instalation manual of theStrand Act 6 dimmer unit it shows how to common the inputs for 1 or three phase supply.

[Andrew C]

Yes (if competent etc).

 

The current drawn will be entirely dependent on what lanterns are on at any one time.  Don't fall into the trap of "if I have these channels at 50% the lanterns draw 1/2 the current" - it ain't so!

[sunray]

In essence the answer is yes. However from your description I've been unable to identify the dimmer or instruction manual.

BUT check the size/capacity of the internal neutral arrangements/connexion. One I repaired was a 12 channel 2KW pack analogue (0-10V control) designed for 3phase 32A supply, the wiring from the inlet 4 bolts was rings of 1.5mm² tri rated, thats a ring feeding 4x 10A MCB per phase and a ring feeding all 12 neutrals. All of that was tightly cable tied into a neat form. It was wired directly to an 80A fuse.

It had been in use for several years until a rather spectacular flash, bang and black smoke stopped the show. Not knowing what it was, SM saw the black smoke and went straight into evacuation announcement.

In 3 phase mode the wiring was only just adequate but in single phase at 80A the neutral would have been overloaded by a factor of >3.

Repair was very simple as it was just cleaning out the debris and replacing/upgrading wiring.

Ever since I've been wary and check internal construction before using 3ph packs on 1ph supplies, regardless of what the instructions say.

 

As a rule of thumb if you use an over current protection device no larger that the rating of one of the 3 phases you should be OK, ie for the 3x32A pack I mentioned a 32A single phase supply should be OK.

 

Andrew has is right, competency is essential and this is an area to not get wrong.
 

[timsabre]

Also, aside from the electrical power considerations, you may need to reconfigure the dimmer's control circuitry in some way to work on single phase if it has been previously used on three phase. The trigger timing for the triacs is different for 3 phase power - some dimmers handle this automatically but some need PCB jumpers or software/menu options to be changed.

Like Sunray I cannot find any info on these dimmers so it's difficult to know how old they are.

[alistermorton]

It appears from your original post that you're running your LED pars off the dimmer packs. Is that right? I'd normally expect to run those on hard power.

[nicholgd]

No led pars are not via dimmers. LED PARs are DMX mains directly.

I cannot find a circuit diagram for the dimmers ,they were made by a Greek company but there is no reference to them on their web site. I will check size of neutral looks comparable to the sum of the three live feeds.

I  will try a low power test with 150 watt lamps to check dimming is Ok. 

It looks like each phase supplies 4 dimmer channels so hope dimming will be ok.

I will ensure a 32 amp is installed.All wireing will be done by qualified and experienced electrician.

Thanks for all the advice.Very much appreciated. 

 

[Stuart91]

23 hours ago, Andrew C said:

Don't fall into the trap of "if I have these channels at 50% the lanterns draw 1/2 the current" - it ain't so!

More out of curiosity than anything - is there a correct answer to this? I'd guess that the triac/switching circuitry draws more power, but for shorter duration?

Thankfully my days of playing Buckaroo with generics are largely over, instead it's managing the leakage from LED fixtures that is the challenge...

[Edward- Z88]

Hi @Stuart91

23 hours ago, Andrew C said:

The current drawn will be entirely dependent on what lanterns are on at any one time.  Don't fall into the trap of "if I have these channels at 50% the lanterns draw 1/2 the current" - it ain't so!

9 minutes ago, Stuart91 said:

More out of curiosity than anything - is there a correct answer to this? I'd guess that the triac/switching circuitry draws more power, but for shorter duration?

Different dimmers will of course all have slightly different curves, but the graph below shows you the power drawn by a 1KW PAR64 when dimmed by an Alphapack 2 dimmer, with a 230v supply:

 

Edward