Run animation motor from dimmer

[techietim]

I'm LD for a local operatic society where the directors wanted a cloud effect across the stage. For that I've got a couple of Rosco 2rpm animation motors with cloud breakups from SE.

 

All OK so far, but I'd like to know if you can run the animation motor from the same dimmer channel as the luminaire it sits in front of. i.e. put a grelco before the luminaire plug and a 15A-13A-IEC or 15A-IEC direct into the animation motor.

 

Reason for asking is that I've not been able to determine what phase the 13A sockets are on which would usually power the animation motors and am concerned they would be different to the Yellow phase the luminaires are on. I don't have enough spare channels on the dimmer to run the motors direct and then use the Jester desk I've got to toggle them on/off.

 

This is my first venture into a venue with 3 phases available (4 x 32A on B, R and 2 x Y phase) and I have been careful to keep luminaires on different phases apart - it's just this that has caught me out!

 

Cheers

Tim

[david.elsbury]

Why do you have to keep the phases apart? It's no longer a part of the regs...

 

You'll most likely be ok with putting the animation motors on a dimmer, the lamp will act as a dummy load.

(as I say, most dimmers are ok with inductive loads. What dimmers do you have?)

[jonathanhill]

It will work, as the lamp will act as a 'load' for the motor, but it is not best practice. If you were to plug the animation motors into the dimmers directly, the motors would run and possibly cause damage to the dimmer depending on age.

 

A concurrent post has been automatically merged from this point on.

 

Why do you have to keep the phases apart? It's no longer a part of the regs...

 

Best practice?

[david.elsbury]

WHY is it best practice though? Please think about your response and give me something better than just throwing around "buzzwords".

 

For example, here in NZ, it's not a problem, not even something we think about. Don't you think that your "best practice" would be followed here if it were actually best practice?

[jonathanhill]

I consider it best practice because 400V hurts.

[KevinE]

It's not good practice because the animation motors will be AC (rather than universal) and firstly not all AC motors will last long if they are run below their rated voltage (because they can stall and their windings take too much current) and secondly because if ever they were connected as the sole load to a dimmer (by accident or otherwise), the load may not be enough to properly latch the thyristors or triac and this could cause a distorted waveform through the windings (half-waving) and again damage them.

 

I'm talking from experience, not hearsay, small synchronous motors can and do fail this way..as they can on certain makes of solid-state switchpacks. It's not inevitable..but the risk is yours, you've been warned!!

[david.elsbury]

But surely if it was considered a problem, it would be in the regs still?

 

Please read this topic...

 

(let's not forget that the OP is planning to put the animation motor on a channel with the luminaire it goes on, a load of at least 500w. Should be more than enough to act as a dummy load.

[jonathanhill]

Whilst I realise that IEE no longer consider this to be a problem, most of the venues that I have worked in in the last 20 years have had a geographical separation of the phases. When specifing, calculating and processing a lighting rig this natural separation has crept into my work. It is now second nature for me to separate phases in the old-school method of allowing 2m separation between bars/areas on differing phases.

 

Sorry if this annoys, but I am too long in the tooth to change now.

[Davethsparky]

WHY is it best practice though? Please think about your response and give me something better than just throwing around "buzzwords".

 

For example, here in NZ, it's not a problem, not even something we think about. Don't you think that your "best practice" would be followed here if it were actually best practice?

 

Reading between the lines a little in the on-site guide, where it says that if outlets on different phases cannot be seperated that a warning label about the prescencee of 400 volts should be fitted, I would have thought it is acceptable to call it best practice to seperate the phases.

I'll look up references once I've got round to knocking the snow off the van and dug out the books.

[Piers Shepperd]

I wouldn't do this for another reason. IF you fade up these projectors slowly, you run the risk of seeing the clouds also spinning up to speed as the lamps come on. As you fade down the projectors the clouds will also start to slow down.

[KevinE]

Well, being synchronous motors, (the clue's in the name) they'll tend to jig and judder at low voltage, then suddenly work at full speed, and then do the same as they're faded down.

 

And lamps blow, so I'll stick with my previous suggestion.

[Ynot]

Reading between the lines a little in the on-site guide, where it says that if outlets on different phases cannot be seperated that a warning label about the prescencee of 400 volts should be fitted, I would have thought it is acceptable to call it best practice to seperate the phases.

I'll look up references once I've got round to knocking the snow off the van and dug out the books.

Oh, fer crying out LOUD!!

There USED to be a spec in the regs which stated phases had to be separated by 2m (6 ft in old money) BUT that was phased out AGES ago as being rather a) impractical to police and b) easy to circumvent, esp without realising.

In industrial situations there is an assumption that the majority of people likely to work on the wiring of installations using 3-ph outlets will have had the training and experience to treat it with the respect it deserves.

And 250v ALSO hurts and can kill just as easily as 440v!

 

Separation of phases is about as commonplace in theatre venues as is the laughable attempt to 'balance' the loads across all 3 phases.

 

We've DONE this, guys - I suggest a search and read up on the topic.

 

As for the OP, I would say DON'T put the wheel motor on the dimmer channel - for the reasons given above regarding motor judder and motor life. Stick it on a constant supply (13A if that's all you have) the motor won't object to being run constantly during the show.

[LXbydesign]

No - dont run the motor through the dimmers - as above -

 

However, if you also dont want the wheels running all through the show, you could always get hold of a DMX switchpack and have control of them that way or failing that, just get an on-stage LX to turn them on and off for you from a 13a supply

[adam2]

I consider it best practice because 400V hurts.

 

400/415 volts does indeed hurt and can be fatal, BUT consider what a large number of improbable faults would have to occur at the same time for anyone to receive a 400 volt shock.

 

Lantern one would have to have no earth (fault 1) and a live conductor touching the case (fault 2)

Lantern two would have to have no earth (fault 3) and a live conductor touching the case (fault 4)

 

And finally if the lanterns are rigged on the same lighting bar or similar support, they are probably earthed via the hook clamp in addition to the CPC in the supply flex.

 

As others post the requirement for 6 feet, latter 2M between phases was abolished many years ago for fixed installations, and enforcement was patchy for fixed installations and non existant for portable equipment.

 

Also note that several popular brands of dimmer pack can be, and often are wired for 3 phase supply.

The average user would neither know nor care that channels 1+2 are on brown phase, 3+4 on black, and channels 5+6 on grey.

 

Almost all dangerous electric shocks are between phase and earth, shocks between phases are very rare.

[techietim]

Thanks for the information and the interesting discussion my query prompted! My 2m apart guide was from Reid's book and I need to learn more about phase difference potentials! It's all hired in kit - DIG 6 dimmers, SL profiles as the projectors.

 

I will stick with the 13A feed and label up to be on the safe side. When we rig I'll just power up the SL to focus it, then when everyone is away from the bar will knock on the motor supply. I'll either run constantly during the show or just get other crew to turn on ready for the scene in question.

 

Thanks again

Tim