5k on 30a 240v dryer outlet?

Alexander Smith · April 23, 2010

Would a high-wattage step down converter like the ones listed in the link below (7500-15000w) modified with the appropriate connectors be able to convert a dryer's (or Honda generator's) 60hz 30a @ 240v to 60hz 60a @ 120v and power a 5k tungsten or 4k hmi?

http://www.voltage-converter-transformers....ransformer.html

John Sprung · April 24, 2010

Search this site for posts from Guy Holt. He does that, and explains it very thoroughly in many threads.

-- J.S.

Christopher Santucci · April 27, 2010

You could just use a 240 volt 5K globe with the 240 volts/30 amps coming from the dryer outlet.

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Guy Holt · April 28, 2010

You could just use a 240 volt 5K globe with the 240 volts/30 amps coming from the dryer outlet.

That is only an option with 5k Fresnels and not an option with other popular luminaries in that range. For instance, a step down transformer will enable you to also operate 2.5 & 4k HMIs with magnetic ballasts, Par 64 Six Lights (6000W), Par 36 Nine Lights (5850W), as well as the new Mole Richardson 5kw Quartz Par off of dryer receptacles and 6500W generators.

The ability to operate the new Mole 5k Quartz Par off of dryer outlets and portable generators is a huge improvement in location lighting. For those not familiar with it, the new Mole Richardson Quartz Par places the lamp on its side and, like an HMI Par, uses a highly polished parabolic reflector and converter lenses to adjust the field of light. Mole has computer engineered the interaction of lamp, reflector and converter lens to maximize the light output from a 5k globe. This fixture is able to achieve output comparable to a standard 14 inch 10K Fresnel, but is similar in size, weight, and design to a 2.5/4k Single Ended HMI Par. The new Mole 5KW Quartz Par puts out as much light as heads twice its size, yet draws only 42 Amps (compared to a 10k’s 84 Amps). However, since it places the lamp on its side it uses a 120V General Electric 5KW Tungsten Halogen lamp specifically designed for Axial Operation. 240 Volt 5k globes can not be used in the new Mole 5KW Tungsten Par. Since it uses a special 120V lamp, you will need a step down transformer to power it from a dryer outlet or 6500W generator.

Guy Holt, Gaffer, ScreenLight & Grip , Boston

Guy Holt · April 28, 2010

Would a high-wattage step down converter like the ones listed in the link below (7500-15000w) modified with the appropriate connectors be able to convert a dryer's (or Honda generator's) 60hz 30a @ 240v to 60hz 60a @ 120v and power a 5k tungsten or 4k hmi?

As John mentioned, I have covered this in other posts in this forum, so I won’t go into details here. For details read my posts:

“How to Plug 5k Quartz & 6k HMIs into wall sockets”

“More Power from Small Generators”

While transformers can offer many benefits, certain features are required in a transformer to make it suitable for motion picture production. The Simran 7500W Power Converter (transformer) you linked in your post has none of those features. It is ill suited for production work.

Simron 7500W Transformer

In developing our HD Plug & Play Pkg. product line, we had considered this very same transformer and ruled it out for a number of reasons. If you look at the pictures I have attached below of the Simran transformer with it’s cover off you will see, that it is a traditional air cooled Open-Core Design in a Nema 1 enclosure that it is only suited for indoor use. Like all transformers it consists of two coils called windings wrapped around a core. A transformer works when a source of AC voltage is connected to one of the windings and a load device is connected to the other. The winding connected to the source is called the Primary. The other winding, which is connected to the load, is called the Secondary.   The Primary is wound in layers directly on a rectangular form. The wire is coated with varnish so that each turn of the winding is insulated from every other turn. When the primary winding is completely wound, it is wrapped with insulating paper. The secondary winding is then wound on top of the primary winding. After the secondary winding is done, it too is covered with insulating paper.

Open-Core Transformer Design

If you look at the transformer in our HD Plug & Play package (pictured below) you will notice it looks quite different. For our HD Plug & Play package we decided instead to use an Epoxy Encapsulated-Core Design Transformer. Epoxy encapsulated transformers use a mixture of silica sand resin and epoxy to completely encapsulate the transformer in a heavy gauge steel casing. Their steel cases are welded and treated with conversion coating before priming and painting to withstand the harshest elements.

Encapsulated-Core Transformer

Encapsulated Transformers offer a number of advantages over open-core designs. The most obvious benefit arises from the physical protection that the encapsulate and outer steel casing provide to the windings, core, and lead connections. With these fragile components sealed in epoxy inside a tough, waterproof casing, encapsulated transformers will withstand the harshest indoor and outdoor applications - making them the clear choice for exterior location production. However, physical toughness and environmental ruggedness are not the only advantages. Constructed of a welded heavy gauge steel casing filled with epoxy, an Encapsulated Transformer forms a single solid mass with no moving or loose parts that can vibrate. Encapsulating the transformer significantly reduces its’ audible noise – another important feature in motion picture production.

A PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 powered by a modified Honda EU6500is through a 60A Full Power Transformer/Distro

The most important benefit to encapsulation, however, is the improvement to the thermal and electrical performance of the transformer that results. Encapsulation greatly improves the transformer’s K-Rating. What is a K-Rating?  It is a value used to determine how much harmonics a transformer can handle without exceeding its’ maximum temperature rise level. Encapsulation is a design element K-rated transformers use to deal with the heat that harmonic generating loads create – an increasing problem in motion picture production today.

Over the past several years there has been dramatic growth in the use of production equipment that generates harmonic distortion. Examples are the AC power supplies of video cameras, lap top computers, video display terminals, battery chargers, and electronic lighting ballasts (HMI & Kino.) These electronic devices contribute to the distortion of the current waveform and the generation of harmonics because they use switching power supplies called SMPSs (an abbreviation for Switch-mode Power Supplies.) SMPSs generate harmonics when they rectify AC line current to DC, and back again in supplying current to the load. In the process, a capacitor is charged then discharged in each half-cycle of the AC line current. This process is repeated 120 times a second. This action of recharging capacitors 120 times per second causes AC current to flow only during the peak portion of the AC voltage wave, in abrupt pulses. These abrupt pulses distort the fundamental wave shape and create harmonic currents, which in turn generate heat in distribution equipment and neutral conductors. If you haven't already, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting. In it I cover some of the basic electrical engineering principles behind harmonic distortion and how it can adversely affect power generation and distribution equipment. The article is available on our website at http://www.screenlightandgrip.com/html/ema...generators.html.

Harmonic currents cause transformers to heat up more than other types of distribution equipment because the currents cycle in their Primary windings. The heat harmonics generate can cause non-K-rated transformers to overheat - possibly causing electrical insulation failure and electrical arcing. K-rated transformers are designed to handle this additional heat and are tested to rigid UL standards. Design features K-rated transformers use to handle the adverse effects of harmonics is double sized neutral conductors, multiple conductors for the coils, more core and coil material, different designs, and different construction techniques like epoxy encapsulation.

Encapsulation is used in K-rated transformers because it greatly improves thermal and electrical performance and consequently the transformer’s K-rating. The mixture of silica sand resin and epoxy compound used for potting has a high coefficient-of-thermal conductivity and is very effective at dissipating heat away from the windings and core; while the heavy gauge steel casing serves as a heat sink. This thermal management reduces winding temperature differentials and allows for the generation of more heat without exceeding allowable temperatures for the insulation class.

Besides causing equipment to overheat, Harmonics can cause device malfunctions, breaker tripping, and excessive vibration. Harmonic currents cycling inside the primary of the transformer can cause Open-Core transformers to vibrate and hum loudly. Epoxy encapsulation dampens the vibration and significantly reduces the hum created by cycling harmonic currents. Encapsulation also increases electrical insulation reliability when compared to tape or paper insulation. Potting is done under vacuum to eliminate air gaps around the windings. With no air around the windings, there is reduced potential for corona and electrical arcing under surge conditions. Even though, K-rating is a heat survival rating, not a treatment of associated power quality issues like voltage distortion, encapsulation can reduce harmonic losses to a slight degree as well.

Finally, in motion picture production it is beneficial to have the transformer compensate for line loss by slightly boosting the voltage output on the secondary side. To assure full line level (120V) on set, our 60A Full Power Transformer/Distro is designed to compensate for the slight line loss you will have over an extended cable run. That is, it is designed to slightly boost the voltage on the load side (secondary) so that if you were to feed the supply side (primary) of the transformer 240 volts from the generator, 127 volts would come out on the secondary side where you plug in the lights. This slight boost enables you to place the generator further from set where you won't hear it, yet assure that the supply voltage on set does not drop too low. This boost enables you to add up to 200' of heavy duty 250V twist-lock cable between the generator and the transformer/distro. This way the generator can be further away, while your plug-in points remain conveniently close to set. You also eliminate multiple cable runs to the generator and the subsequent drop in voltage from line-loss from using standard electrical cords.

The Simran 7500 you link to steps down/up voltage in a fixed 2:1 ratio. As specified on their website, if you feed the supply side 240 volts you get exactly 120V on the load side. If you feed the supply side 220 volts you get exactly 110V on the load side. If you were to put a fixed 2:1 ratio transformer, like this Simran 7500, at the end of a 200’ cable run, the line loss over the long cable run, may result in a line level on set that is too low. For this reason alone the Simran 7500W Power Converter (transformer) is ill suited for production work with generators. Encapsulated-core boost transformers like the one we use in our HD P&P Pkg, are ideal for use with generators and for motion picture production applications in general. Use this link - http://www.screenlightandgrip.com/html/hd_...n-play_pkg.html - for more details about using step-down transformers to power larger lights on interior sets.

Guy Holt, Gaffer, ScreenLight & Grip , Boston

John Sprung · April 28, 2010

The winding connected to the source is called the Primary. The other winding, which is connected to the load, is called the Secondary.   The Primary is wound in layers directly on a rectangular form. The wire is coated with varnish so that each turn of the winding is insulated from every other turn. When the primary winding is completely wound, it is wrapped with insulating paper. The secondary winding is then wound on top of the primary winding.

Finally, in motion picture production it is beneficial to have the transformer compensate for line loss by slightly boosting the voltage output on the secondary side. To assure full line level (120V) on set, our 60A Full Power Transformer/Distro is designed to compensate for the slight line loss you will have over an extended cable run. That is, it is designed to slightly boost the voltage on the load side (secondary) so that if you were to feed the supply side (primary) of the transformer 240 volts from the generator, 127 volts would come out on the secondary side where you plug in the lights.

The secondary doesn't have to be physically wound outside the primary. Which is which depends only on how you connect the line and load. For instance, if you were to put power into the 120 volt side of these transformers, you'd get 240 out the other side. The transformer is just two coils and a core, it has no way of knowing or caring which way around you hook it up. Where this gets really important is if you use a small generator at home during a power failure. It's illegal in most places to connect a generator to the wiring in your house, because you can back feed the utility transformer and kill the guys who are trying to fix your power. Permanently installed emergency generators are required to feed through a transfer switch to prevent this.

Guy, do you get your 240:127 from a multi-tap transformer? Years ago on the Universal lot, I remember they used to shift taps at their substation twice a year, because they needed the boost during air conditioning season.

-- J.S.

Guy Holt · April 28, 2010

Guy, do you get your 240:127 from a multi-tap transformer? Years ago on the Universal lot, I remember they used to shift taps at their substation twice a year, because they needed the boost during air conditioning season.

We don't use a multi-tap transformer because it would make the transformer larger and heavier. Instead we have them made specifically 240/127 because we know that the applications in which they will be used will have some line loss.

Guy Holt, Gaffer, ScreenLight & Grip, Boston

John Sprung · April 29, 2010

Wow -- Custom winding transformers. You really went Rolls-Royce style on this.

-- J.S.

Hal Smith · April 29, 2010

Search ebay for what electrical companies call a "dry transformer". Either winding of a dry transformer can be the primary while the other is the secondary. There are some differences in primary and secondary design but not enough to be an issue at the sizes of transformers likely to be used around movie lights.

For reference: http://www.mgmtransformer.com/faq.html

Isabelle Landers · April 30, 2010

Search ebay for what electrical companies call a "dry transformer".

I searched ebay under "dry transformer" as you suggested. Even though I got a lot of returns, none of them fit Guy's description of an epoxy encapsulated K-rated 240:127 boost transformer. From what I understand from the websites I have read (including the link you provided) that particular configuration 240:127, verses the standard 240:120 configuration, is custom just like John says in his post. Apparently there is something to what Guy says in his post about motion picture production requiring a custom configuration.

Isabelle Landers, Gaffer, Nashua, NH