generator limitations

[joe copage]

We have a shoot next month and need to run lights off a generator. Because of a limit on space we have to use a small diesel generator. The genie is 3 phase and a max output of 16kva. The lights we are aiming to use are: 1.2 HMI, 2.5 HMI and 3 red heads?

Thanks.

Joe

[Ed Conley]

You'll be ok with that generator.

 

It is a small genset so how is the power distributed? Does it it have camlock to be able to feed a Distro box?

 

The only item of concern is feeding the 2.5 with a 60amp Bates connection.

[Michael E Brown]

You'll be ok with that generator.

 

It is a small genset so how is the power distributed? Does it it have camlock to be able to feed a Distro box?

 

The only item of concern is feeding the 2.5 with a 60amp Bates connection.

 

The 60a bates is oversized for a 2.5k, it's just the next size up in standardized plugs.

 

With the genny running in three phase (3 pole) mode with a non-PFC ballast, it should be fine. The other option is to run the genny in single phase (2 pole) mode so that you get 50% more current per leg for high draw lights.

 

PFC 2.5k is only like 23-24 amps - would not be a problem at all.

[Ed Conley]

Every 2.5 I have used has a 60amps bates Connector on the ballast feeder- I know they don't draw that much power but the connector is a 60amp bates.

 

At least the ones I have used.

 

:)

[JD Hartman]

The generator head would have to be a 12 lead, to be re-configurable to single phase. Even if it was said animal, they aren't usually switch selectable for good reason. Be sure the unit you rent has camloks or lugs and not something like 50a "California Style" twistlocs.

[Michael E Brown]

Every 2.5 I have used has a 60amps bates Connector on the ballast feeder- I know they don't draw that much power but the connector is a 60amp bates.

 

At least the ones I have used.

 

:)

 

Ed, you are correct. I was simply pointing out that just because a light has a 60a plug, doesn't mean it draws 60a. That's the next size up from 15/20a plugs in the standardized world so there isn't much choice.

[Michael E Brown]

The generator head would have to be a 12 lead, to be re-configurable to single phase. Even if it was said animal, they aren't usually switch selectable for good reason. Be sure the unit you rent has camloks or lugs and not something like 50a "California Style" twistlocs.

 

If a rental company brings you anything but a 4 pole, 12 lead genset - they are living in the 80s. Probably towing it with a Mack truck also.

 

Both the major brands (Burrell's LitePOWER and Multiquip's WhisperWatt/Crawford) used in production definitely have single/three phase switch selection. On MQs, it's usually located inside above the tie in connections. The switch has a lock button below the switch that keeps it from being moved while the generator is running. You can switch from single phase to three phase in about 2 seconds.

[John Sprung]

If a rental company brings you anything but a 4 pole, 12 lead genset - they are living in the 80s. ..... You can switch from single phase to three phase in about 2 seconds.

 

That's when I was alive.... ;-)

 

Not having had a switchable generator in my working days, I'm wondering why would you choose three vs. single phase for lighting? I know the three phase advantages for motors, but what are the pros/cons for lights?

 

 

 

 

 

-- J.S.

[Michael E Brown]

That's when I was alive.... ;-)

 

Not having had a switchable generator in my working days, I'm wondering why would you choose three vs. single phase for lighting? I know the three phase advantages for motors, but what are the pros/cons for lights?

 

-- J.S.

 

I would say it's dictated by the type of distribution system you have available more than anything else, except for a few special circumstances.

 

If you only had single phase generators available, that's what the distribution was. Some small trucks still carry only single phase distribution so the flip side is if all you have is single phase distribution/cables - then you run the generator in single phase mode. That also means you can rent a smaller generator for a single phase truck (plus it's balanced, unlike hanging 2 legs off a 3 phase genset).

 

Most choose three phase for the simple fact that with US standard connections - you can get 50% more power. Using typical 400a camlocks limits you to 400a/leg - so you only have 800a total available with a single phase system vs. 1200a with a three phase system. There are larger connectors (and super heavy wire) available, but the 400a camlock is the standard and pretty much sets the max current per leg.

 

One reason to choose single phase OVER three phase is the example I stated first in this thread: your generator isn't large enough to power a large head. If you choose single phase mode, you get 50% more current on each leg - possibly allowing you to plug in a large HMI or tungsten fixture that otherwise would be too large for the genset at hand. Say you had a generator that was rated at 30a/leg three phase or 90a total but needed to plug in a 40a light. Switching the generator to single phase would now give you 45a/leg so you could plug that light in.

 

Another reason to choose single phase OVER three phase is leg-leg voltage. If you have some older ballasts or xenon gear that really wants 240v instead of 208v - single phase would help. Now many companies send out buck-boost transformers with gear that HAS to have 240v like some xenon stuff so you can run it on 208v anyway.

[John Sprung]

Thanks, Michael -- That's the kind of detail you can only get from a working professional.

 

Back in my day, distribution consisted of spider boxes with 1/4" thick copper bars in them, and 50 ft. pieces of 4/0 cable with brass lugs. The lugs clamped onto the bars with those setscrews with the 5/16" square heads. (IIRC, it was 5/16") We used to carry little 6" Crescent wrenches for that. I think I still have a pile of those brass lugs in the garage someplace....

 

 

 

 

-- J.S.

[Guy Holt]

The genie is 3 phase and a max output of 16kva. The lights we are aiming to use are: 1.2 HMI, 2.5 HMI and 3 red heads?

 

With the genny running in three phase (3 pole) mode with a non-PFC ballast, it should be fine. . . PFC 2.5k is only like 23-24 amps - would not be a problem at all.

 

I have to agree with Ed Conley

 

You'll be ok with that generator… The only item of concern is feeding the 2.5 with a 60amp Bates connection.

 

Small gen-sets like these don’t use camlocks so you can’t feed a film standard distro box? They are typically outfitted with two (2) 120V-20 amp GFCI duplex receptacles, Two (2) 240V-30 amp twist lock receptacles, and Two (2) 240V-50 amp twist lock receptacles.

 

The problem Joe faces is that most 2.5 ballasts are configured to operate at 120V and are wired with a 60A Bates, even though the electronic ballasts can operate 240V. At 120V a Magnetic ballast will draw 28A, a Non-PFC Electronic ballast will draw 35A, and a PFC Electronic ballast will draw 23A. Where none of these ballasts will run on the 120V outlets provided on the generator, you have two options. You must either use an electronic ballast that will also operate 240V and replace it’s 120V 60A Bates plug with a 240V-30 amp twist lock receptacle of the same NEMA configuration as the generator output panel; or use a 240v-to-120v step down transformer like the one we manufacturer for our modified Honda EU6500is generators that put out 7500W.

 

A transformer will convert the 240 volts supplied by 240V-30 amp receptacle back to 120 volts in a single circuit that is the sum of the two legs of the circuit. For instance, a 7.5KVA transformer will make a 60A/120v circuit out of the generator’s 30A/240v circuit that is capable of powering bigger lights, like a 2.5kw at 120V regardless if it is a magnetic or electronic ballast.

 

If you do not familiar with the use of transformers, use this link - http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorTransformer/Distros%20verses%20Splitter%20Boxes - to a technical article I wrote for our company newsletter that explains how to use step-down transformers on set. .

 

 

This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." Of the article Harry Box exclaims:

 

"Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

 

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."

 

Since a transformer, in addition to enabling Joe to power his 2.5kw, can also give you access to more house power through common 240V house outlets, often eliminating the need for tie-ins or generators, it is well worth reading. The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

[Michael E Brown]

Small gen-sets like these don’t use camlocks so you can’t feed a film standard distro box? They are typically outfitted with two (2) 120V-20 amp GFCI duplex receptacles, Two (2) 240V-30 amp twist lock receptacles, and Two (2) 240V-50 amp twist lock receptacles.

 

This may be a geographical thing, but all the small rental units around me (Southeast) have the bare wire tie in option along with the twist locks (it's a factory option on the MQ units, not sure about LitePower). So one just needs to make sure there are Cam to bare wire tails available, which of course is standard. I would think a unit without any way to tie in other distribution would be something used mainly in construction, etc which I wouldn't not want to use on a set anyway since they tend to be poorly maintained.

 

Now, I've never seen a 16KVA unit - only 20 and 25 so I can't say for certain about them. A quick Google search actually indicates that the 16KVA size would be more common in Europe, so the connections may be considerably different anyway.

 

The OP really needs to give some additional information in order for anyone to get specific.

[Guy Holt]

Now, I've never seen a 16KVA unit - only 20 and 25 so I can't say for certain about them. A quick Google search actually indicates that the 16KVA size would be more common in Europe, so the connections may be considerably different anyway.

 

Don't lump a 16KVA generator with larger units like the Multiquips - the smallest of which is a 25KVA. There is not much need for bare end lugs on a generator that puts out only 37Amps a leg. They are more similar to a large Honda than a Multiquip, and you don't see bare end lugs on Hondas. They are configured how I have described them above. 16KVA generators are very common in this country. They are principally used in road construction and will quite often have a light tower attached.

 

I agree, the OP really needs to give some additional information on how the particular 16KVA generator he will be using is configured in order for anyone to get specific. Short of that a step-down transformer is a guaranteed option.

 

- Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental in Boston

Edited October 12, 2010 by Guy Holt

[joe copage]

Hi guys, thanks for all the input, unfortunatly the 16kva diesel generator we had broke down just before the shoot so we had to run off 2 x 5kva petrol genies, The lack of space was due to the genies being on a wakeboard boat. we rigged 2x 800w and a 2k on the boat and from the shore we used a 2.5 and 1.2 hmi's. This was a personal project for me.any feed back much appreciated.

thanks

joe.