Sensor vs ET Intelligent Raceway

[Van]

Sorry, but I don't agree with your view about an IGBT dimmer dealing well with many different load types. History proves differently.

The ET IGBT dimmer operates in either forward or reverse phase control mode. A load with any inductive component cannot be used with reverse phase control. Either you manually force the dimmer into forward phase control mode for such a load, or you rely on the dimmer's internal sensing of the inductive load to automatically switch to forward phase control. This does not always work perfectly, in my experience. The result can be a failure.

Now a well designed sine wave dimmer that uses IGBT's as the power devices is a different story. That type of dimmer has wide tolerance of a lot of "odd loads".

In fact, SCR dimmers are quite tolerant of many types of resistive, inductive, and capacitive loads.

As your your "safety" comment--please elaborate, since right now I see no basis in fact or history behind that statement.

ST

I have never NEVER had a failure, nor have I heard of a case in which an ET IPS dimmer failed to correctly identify a load type. While you can run an inductive or capacitive load on an SCR based dimmer you must needs have a dedicated dimmer type to do so.

Safety? IGBT dimmers will "clamp" to a dead short faster than a circuit breaker, and that ability is not diminished over time by corrosion, and it doesn't get "loose" like a breaker either. I think the safety issue is rather self evident.

 

[STEVETERRY]

I have never NEVER had a failure, nor have I heard of a case in which an ET IPS dimmer failed to correctly identify a load type. While you can run an inductive or capacitive load on an SCR based dimmer you must needs have a dedicated dimmer type to do so.

Safety? IGBT dimmers will "clamp" to a dead short faster than a circuit breaker, and that ability is not diminished over time by corrosion, and it doesn't get "loose" like a breaker either. I think the safety issue is rather self evident.

I'm glad to hear you have never had a failure--that's a great endorsement! Others have not had the same experience, however.

Electronic short circuit protection is a requirement of an IGBT dimmer due to the relative fragility of the power device itself in the presence of a short circuit. A circuit breaker cannot act fast enough to protect the IGBT. This speed, however, does not translate into "safer".

In fact, UL does not accept electronic short circuit protection as the only overcurrent device--they require an upstream breaker or fuse. In the case of the product we are discussing, that is a standard thermal/magnetic breaker in a panel. That breaker is only rated for 80% continuous loading rather than the 100% of a typical fully-magnetic breaker on a professional dimmer rack.

This raises another compromise: the raceway system has two 2.4kW dimmers fed from single 20A feed, so the maximum aggregate load across the two dimmers is advertised as 2.4 kW. In reality, if this system is fed from a 20A thermal/magnetic breaker in a panelboard, the aggregate maximum load across the two dimmers is only 1920W continuous, due to the inherent 80% rating of the breaker.

That means that two adjacent dimmers cannot support 2 x 575W continuous loads each, when both dimmers are on. This may be too much of a derating compromise for some users.

Finally, there has been some discussion here about heat. The heat load of the distributed dimmer is insignificant compared to the heat load of the lamp it is driving. So, we don't need to worry about bigger air conditioning in a space for distributed dimmers.

However, the sensitivity of an IGBT convection-cooled dimmer to increased ambient temperatures in much greater than that of a rack SCR dimmer. The product we are discussing deals with that by reducing its rise time (or fall time when operating in reverse phase control mode). That means than an advertised rise time of 500 or 800 microseconds may be considerably less than that when the dimmer is fully loaded and operating in elevated ambient temperatures caused by being in close proximity to lots of hot lights. That means noisier filaments under those conditions, another compromise that potential purchasers need to be aware of.

ST

 

[SteveB]

This raises another compromise: the raceway system has two 2.4kW dimmers fed from single 20A feed, so the maximum aggregate load across the two dimmers is advertised as 2.4 kW. In reality, if this system is fed from a 20A thermal/magnetic breaker in a panelboard, the aggregate maximum load across the two dimmers is only 1920W continuous, due to the inherent 80% rating of the breaker.
ST

Steve, 2 comments/questions:

1) If I understand the ITS literature correctly, you feed 3 - 2.4kw dimmers with a single 20amp, 3 pole breaker (3 hots, 1 neutral). On the raceway series, you can split loads across a 2.4kw, to be 2 dimmed circuits, loading either side as desired, up to the max. capacity of the single non-split dimmer. The dimmer strips and packs need to be pre-selected and purchased as either 3x2.4kw dimmers or 6x1.2kw dimmers, which are still fed via 1-20amp, 3 pole panel breaker per every 3 or 6 dimmers. The raceway design is seemingly advantageous if the load is expected to be individual fixtures per dimmer at 575 or 750 watts, as you can load up 96 fixtures, each on individual dimmers on a 96ft. raceway, or whatever length is appropriate. In this case the de-rating of the panel breakers is an issue for 1kw loads, but not for lesser loads, which in my mind is a good reason to throw out all those old 1kw PAR64's for ETC S4 Pars (grin).

2) Are standard panel mount industrial type breakers (as opposed to the typical breaker on Sensor dimmer or relay), available as 100 percent continuous loading ?. This de-rating due to distro. panel requirements can be a deal breaker in some cases, IMO.

3) If the desire, and the ETC Load Survey seems to support this, is individual fixtures @ 575w, 750w, but NOT 1000w loads, ea. on individual dimmers, then the ITS IGBT system is attractive to a system designer/end user. All things being equal, I could see recommending this design if the architecture supported fixtures in this wattage size(s), such as FOH coves or catwalks, where the flexibility of having 2.4kw circuits is not required (I cannot fit a 2kw fixture in my coves, as example).

Just some food for thought.

Steve Bailey
Brooklyn College

 

[STEVETERRY]

Steve, 2 comments/questions:

1) If I understand the ITS literature correctly, you feed 3 - 2.4kw dimmers with a single 20amp, 3 pole breaker (3 hots, 1 neutral). On the raceway series, you can split loads across a 2.4kw, to be 2 dimmed circuits, loading either side as desired, up to the max. capacity of the single non-split dimmer. The dimmer strips and packs need to be pre-selected and purchased as either 3x2.4kw dimmers or 6x1.2kw dimmers, which are still fed via 1-20amp, 3 pole panel breaker per every 3 or 6 dimmers. The raceway design is seemingly advantageous if the load is expected to be individual fixtures per dimmer at 575 or 750 watts, as you can load up 96 fixtures, each on individual dimmers on a 96ft. raceway, or whatever length is appropriate. In this case the de-rating of the panel breakers is an issue for 1kw loads, but not for lesser loads, which in my mind is a good reason to throw out all those old 1kw PAR64's for ETC S4 Pars (grin).

2) Are standard panel mount industrial type breakers (as opposed to the typical breaker on Sensor dimmer or relay), available as 100 percent continuous loading ?. This de-rating due to distro. panel requirements can be a deal breaker in some cases, IMO.

3) If the desire, and the ETC Load Survey seems to support this, is individual fixtures @ 575w, 750w, but NOT 1000w loads, ea. on individual dimmers, then the ITS IGBT system is attractive to a system designer/end user. All things being equal, I could see recommending this design if the architecture supported fixtures in this wattage size(s), such as FOH coves or catwalks, where the flexibility of having 2.4kw circuits is not required (I cannot fit a 2kw fixture in my coves, as example).

Just some food for thought.

Steve Bailey
Brooklyn College

1. My understanding is that in the raceway system 6 x 2.4 kW are fed from a 3-phase 20A feed. Any one dimmer can be loaded to 2.4kw, but pairs can only be loaded to 2.4kW total.

2. While there are 100% electronic-trip breakers available, I am not aware of any at the 20A level.

3. I like derating as much as the next guy--but I want to choose where to derate. If we are accepting 1.2kW dimmers for a good reason--like less expensive sine wave dimmers where absolute silence is required--fine. But if we're dropping the power on a non-sine-wave dimmer, given that a 1.2kW SCR dimmer costs the same as a 2.4kW SCR dimmer--I can't see the logic.

I want to be able to put 2.4kW loads wherever I want--as long as I'm not compromising for the quiet of cost-reduced sine wave dimmers.

Let's remember that the noise performance of an IGBT dimmer operating in forward phase control mode is identical to that of the equivalent rise-time SCR dimmer. And the noise performance of a reverse phase control IGBT dimmer is not equivalent to a sine wave dimmer.

ST

 

[SteveB]

ST Wrote:

"1. My understanding is that in the raceway system 6 x 2.4 kW are fed from a 3-phase 20A feed. Any one dimmer can be loaded to 2.4kw, but pairs can only be loaded to 2.4kW total."

Well THAT makes no sense !. On a system where I might spec. 32x2.4KW Sensor circuits, they would put in a raceway with 32x2.4kw IGBT's (that "Or Approved Equal" clause), but only provide power to load ea. dimmer at 50%, or have 64 split dimmers at 1.2kw, but really ony 600 watts ea. Maybe I'm not getting it, but I would be very un-happy with that design.

A very preliminary design for our new building showed the renovated theater as having 2 dimmer racks - presumably the typical 96x2.4kw rack(s), ea. fused at 400 amps, 3 phase, per rack. I've been down this road before, and won the last time, when I pointed out that sizing the feeds and main breaker at this rating essentially down rates ea. 2.4kw dimmer by approx. 30% or so, or basically ea. dimmer becomes a 1.8kw. I believe it was ST who recommended to me (advise we followed) to fuse at 600 amps per rack, with 800 total for 2 racks, so at least we could load up a "zone" of the theater if needed. Steve, I believe you wrote a trade journal article about this subject a few years (decades ?) ago.

Which brings up the question - All is fine and well when you have a Sensor 48, with 96x2.4kw dimmers, all rated at 100% continuous load, but is the main breaker, be it a 600 or 800 3 pole, now downrated by 20% ?. If that's the case, I would and can make the case that all racks shall be fed from 600 amp main breakers.

"3. I like derating as much as the next guy--but I want to choose where to derate. If we are accepting 1.2kW dimmers for a good reason--like less expensive sine wave dimmers where absolute silence is required--fine. But if we're dropping the power on a non-sine-wave dimmer, given that a 1.2kW SCR dimmer costs the same as a 2.4kW SCR dimmer--I can't see the logic."

I could see the logic if we were following the implications of the load survey, and stopped using 2.4kw circuits in a lot of places that don't need them, then could save on wiring costs by running #14 wire, instead of #10. If it were a rack with 192 x 1.2kw dimmers in the space of a 96x2.4, then when combined with the smaller wiring, the costs come down a lot. Trouble is, I doubt the New York City electrical (or Nat'l Code for that matter) would allow me to run 10 amp branch circuits for stage lighting, as I believe 20 amps is the minimum.

But a thanks to ST for some very informative comments and as usual I learned a bunch.

Steve B.

 

[STEVETERRY]

ST Wrote:

"1. My understanding is that in the raceway system 6 x 2.4 kW are fed from a 3-phase 20A feed. Any one dimmer can be loaded to 2.4kw, but pairs can only be loaded to 2.4kW total."

Well THAT makes no sense !. On a system where I might spec. 32x2.4KW Sensor circuits, they would put in a raceway with 32x2.4kw IGBT's (that "Or Approved Equal" clause), but only provide power to load ea. dimmer at 50%, or have 64 split dimmers at 1.2kw, but really ony 600 watts ea. Maybe I'm not getting it, but I would be very un-happy with that design.

A very preliminary design for our new building showed the renovated theater as having 2 dimmer racks - presumably the typical 96x2.4kw rack(s), ea. fused at 400 amps, 3 phase, per rack. I've been down this road before, and won the last time, when I pointed out that sizing the feeds and main breaker at this rating essentially down rates ea. 2.4kw dimmer by approx. 30% or so, or basically ea. dimmer becomes a 1.8kw. I believe it was ST who recommended to me (advise we followed) to fuse at 600 amps per rack, with 800 total for 2 racks, so at least we could load up a "zone" of the theater if needed. Steve, I believe you wrote a trade journal article about this subject a few years (decades ?) ago.

Which brings up the question - All is fine and well when you have a Sensor 48, with 96x2.4kw dimmers, all rated at 100% continuous load, but is the main breaker, be it a 600 or 800 3 pole, now downrated by 20% ?. If that's the case, I would and can make the case that all racks shall be fed from 600 amp main breakers.

"3. I like derating as much as the next guy--but I want to choose where to derate. If we are accepting 1.2kW dimmers for a good reason--like less expensive sine wave dimmers where absolute silence is required--fine. But if we're dropping the power on a non-sine-wave dimmer, given that a 1.2kW SCR dimmer costs the same as a 2.4kW SCR dimmer--I can't see the logic."

I could see the logic if we were following the implications of the load survey, and stopped using 2.4kw circuits in a lot of places that don't need them, then could save on wiring costs by running #14 wire, instead of #10. If it were a rack with 192 x 1.2kw dimmers in the space of a 96x2.4, then when combined with the smaller wiring, the costs come down a lot. Trouble is, I doubt the New York City electrical (or Nat'l Code for that matter) would allow me to run 10 amp branch circuits for stage lighting, as I believe 20 amps is the minimum.

But a thanks to ST for some very informative comments and as usual I learned a bunch.

Steve B.

A main breaker is a thermal/magnetic device rated at 80% continuous load, unless it is specified as a 100%-rated electronic-trip breaker.

On a two-rack system, I would buss them together and feed from a single 800A breaker.

ST

 

[derekleffew]

... I believe it was ST who recommended to me (advise we followed) to fuse at 600 amps per rack, with 800 total for 2 racks, so at least we could load up a "zone" of the theater if needed. Steve, I believe you wrote a trade journal article about this subject a few years (decades ?) ago.

Summer 2002, in the ESTA quarterly, Protocol. See attached. Any revisions you would make today, Mr. Terry?

...As other have pointed out, there are many ML's wanting 208v, though I question as to the application of the larger and brighter ML's that need 208, being needed in smaller spaces. You still need "some" 208 around, so best plan for it, but I have a question - are the fixtures needing 208, using 208 only because they are brighter ?, or is the feature set of the larger fixtures what people are after ?...

Not just because they are brighter, although that's a prime reason. Just as because of the CompactDisc, audiences demand hifi sound; seemingly more onstage lumens are required for each production. We're talking theatre, and theatre requires hard edge fixtures with shutters, right? So the choices are Revolution or VL1000T in the incandescent range; and VL1000A, MAC2000Performance (120V or 208V) or VL3500SPOT (208V only).

 

[STEVETERRY]

Summer 2002, in the ESTA quarterly, Protocol. See attached. Any revisions you would make today, Mr. Terry?

Only that it is probably somewhat extravagant to use a full size main breaker on each rack fed by a de-rated main. A much more economical approach is to use factory-bussed racks and a single de-rated main breaker. You lose the advantage of a separate disconnect for each rack and the associated fault propagation control, but it sure gains you a lot of dollars in switchgear and labor to go with the bussed system. And it changes nothing in terms of your derating philosophy.


In addition, the recently-available Harmonic Mitigating Transformer (HMT) is a preferable option to a K-rated transformer for feeding a phase-control dimming system. See Transformer, Harmonic Mitigating in the Glossary for details.

ST

 

[SteveB]

Only that it is probably somewhat extravagant to use a full size main breaker on each rack fed by a de-rated main. A much more economical approach is to use factory-bussed racks and a single de-rated main breaker. You lose the advantage of a separate disconnect for each rack and the associated fault propagation control, but it sure gains you a lot of dollars in switchgear and labor to go with the bussed system. And it changes nothing in terms of your derating philosophy.


In addition, the recently-available Harmonic Mitigating Transformer (HMT) is a preferable option to a K-rated transformer for feeding a phase-control dimming system. See Transformer, Harmonic Mitigating in the Glossary for details.

ST

Can you say "Cut and paste" ?.

Actually, I was just writing the section as to how the transformers planned should be K rated, which is now HMT

I'm sure the consultant is now going to have to do some research - What the hell is a "Harmonic Mitigating Transformer" ?. (grin),

So a big Thank You.

SB

 

[STEVETERRY]

Can you say "Cut and paste" ?.

Actually, I was just writing the section as to how the transformers planned should be K rated, which is now HMT

I'm sure the consultant is now going to have to do some research - What the hell is a "Harmonic Mitigating Transformer" ?. (grin),

So a big Thank You.

SB

Tell him to look at the websites for Powersmiths: Powersmiths - Power for the Future or Mirus: Mirus Harmony Transformers.

You can also send him a copy of my "New Power Tools" article on the subject, which has a link in the glossary entry: http://www.controlbooth.com/forums/glossarys/9011-transformer-harmonic-mitigating.html.

ST

Edit by DL: See also the articles referenced in the glossary entry: Harmonics.

 

[derekleffew]

Not intending to open any healed wounds, but felt the following from a non-partisan individual on the Light Network might be pertinent, and beneficial to the discussion:

As an early experimenter in FET and IGBT dimming, there are some problems that need
to be understood. These are problems that usually don't affect theatrical style lighting.
They can be a problem for fllash and dash. Mind you, these are all problems that confront
normal SCR dimming; we've just gotten away with them.
Classic dimmer design applied overall feedback around the dimmer. This provided for
predictable curve and response, and improved line and load regulation. Most modern
digital designs use line regulation only, with varying success. I believe that ETs use overall feedback. But a modern digital dimmercan be FAST. The only limitation is when the next half cycle comes around.
It should be understood that incandescent lamps are not a linear load. The impedence of
the lamp drops significantly as the lamp cools. A lamp driven by 50% voltage draws
considerably more than 50% of its rated current. A dead cold PAR switched on at the peak
of the AC line voltage may draw somewheres around 12X its rated current. This current
spike may last only for part of a half cycle, but it may take 5 or 6 cycles before the lamp reaches operating temperature. With an SCR IsquaredT ratings of 500 are possible in
an SCR used in a 20A dimmer. The SCR can take a vast overload for a few milliseconds.
Which is good since we have no way to turn it off until the zero crossing. SCR dimmers can be protected by the choke and a circuit breaker. You don't have that luxury with FET dimming. Current limiting must be nearly immediate and the inrush current of a dead cold lamp limited.
I knew a club in NYC whose walls were lined with hundreds, if not thousands, of standard A bulbs. There was also a large theatrical rig, including a lot of early Vari-Lites. On the
conventional console there was one bump button pinned to flash all the conventionals.
Pushing this button when the system had not been used for 12 hours would cause serious
mechanical stresses on the buss bars of the 1200 A 3 phase entrance. You could hear the buss bars trying to rip loose 3 floors up. It was a great blink effect. There was no current limiting and no slow response. But the disturbance this produced on the local electric grid was not pretty. If I was Con Edison, I'd have had words with the club. (Or at least my
friend, the head tech. You know who this was, Fester.....)
The day is coming when the power companies will not want us to blink the way we do now.
And switching to generator power won't be the answer either - I nearly stalled a large
Rolls Royce generator accidentally doing the same thing.
So you gotta pick your dimmers to suit your needs. Bob Goddard
Goddard Design Co.

 

[SteveB]

What I found especially amusing is that one of the selling points for IGBT is that they provide "Dead Short Protection". What they don't tell you is that the circuit HAS to have Dead Short Protection.

Kind of like Airbus making a selling point of how well their airplanes float.

SB

 

[STEVETERRY]

What I found especially amusing is that one of the selling points for IGBT is that they provide "Dead Short Protection". What they don't tell you is that the circuit HAS to have Dead Short Protection.

Kind of like Airbus making a selling point of how well their airplanes float.

SB

Want a job in ETC marketing?



ST

 

[SteveB]

Want a job in ETC marketing?



ST

Sure, but you're gonna have to put up with endless questions like "When does the temperature go above -20" and "Where's the ocean ".



SB

 

[derekleffew]

SteveB and SteveT could carpool/[-]planepool?[/-]/share the corporate Gulfstream jet.

 

[SteveB]

SteveB and SteveT could carpool/[-]planepool?[/-]/share the corporate Gulfstream jet.

Yeah, and those Fred F paid-for junkets to Florida and the Bahamas, that all the senior ETC VP's take advantage of regularly.

From company e-mail "The jet for Fridays meeting on the Ion Jr. will be leaving at 7AM SHARP".

SB