Week 160 (Variac Panel)

Some things take longer than others.  A little more than two years ago I advertised that the studio would be using Variac transformers instead of more modern technologies.  This was not a “retro at all costs” decision (though Variacs can be used to provide a really, really great dimming system), but due to the the fact that the pre-eminent lighting control company refused to sell us the very reasonable and very standard system that virtually every other studio employs, and instead would only quote us a package that cost 200% more than it should have.  Their absolute unreasonableness caused us to design them out of the main studio, albeit at an extraordinary expense of time.   Our proven ability to design around them led to a very easy negotiation the next time around when it came to outfitting the Annex.  Go figure.  But now, the variable transformers that we procured in 2008 are finally now being installed:

The design is ultra-green (in my book), as follows…

First off, Variacs are tremendously efficient at dimming because they change voltage without using resistance.  Conventional rheostats use a constant amount of power and merely control whether the energy comes out of the lamps or out of the heavy-duty resistors in the walls.  A step up are switching controlled rectifiers that overlay a variable high-frequency pulsed duty cycle over top of the normal 60Hz duty cycle of AC voltage.  Energy only flows when the duty cycle is on, hence a short duty cycle really does reduce the amount of energy used.  But it’s not ideal: there’s energy loss as the switches turn rapidly on and off, but worse, the high-frequency switching introduces a huge amount of harmonic noise, and in a studio environment large debuzzing coils are needed to control that noise.  But the best solutions are the ones that don’t create problems in the first place.  Variacs work on the simple principle of a variable ratio of primary and secondary transformer coils; the frequency of operation remains a solid 60Hz (no change there), and transformer loss is typically less than 5%, so they are very efficient.  And quiet.

The innovation you see above adds a switch that either engages the transfomer, breaks the circuit, or completes the circuit but bypasses the transformer.  The transformer’s loss is greatest when operating at full power: 5% of 1000W is 50W of loss.  Bypassing the transformer at full power means we don’t suffer that loss.  If dimming is required, we can engage the transformer and turn down the voltage.  At 50% voltage, we lose only 25W per circuit.  Not so bad!  Here’s a detailed view of the back side of one of those switches:

The two Variac sizes you see are 10A (larger) and 5A (smaller).  Two of the Variacs are now operational (and quiet!), and the remaining ones should be hooked up very shortly.

In other wiring-related news, hundreds of more wires have been terminated in the QR, and we have begun placing equipment into racks to give those terminations something to attach to.  A Trinity clocking unit provides a home to many terminations:

Elsewhere you can see the steady progress of the wiring team:

Here’s the back side of a CAT6 wiring panel that’s about to be filled with connections:

The trick is to make progress every day.

Elsewhere, the fascias of the Music Room, Control Room, and Booths A and B have all been completed.  Here’s a nice fascia from the Music Room:

And here’s a flash making the beautiful cherry in the Control Room look ugly:

Meanwhile, we’re back in the business of pouring concrete.  Since Thanksgiving (late November 2010) we have not had two days in a row with temperatures above freezing.  Such is perfectly in keeping with the average winter night-time temperature in North Carolina, but what is not normal is for there to be so little variation over a 60 day period.  Usually there are entire weeks of warm weather that come like blessings to December, January, and February, but we have had no such luck this year.  And we have basically run out of patience waiting for ideal concrete-pouring weather.  This week we did have some warm days, and we made the nights warmer by tenting our pours and protecting them from the cold, clear air:

Under the tent, concrete is poured, stained, and ready to be worked:

A second pour completes the tip of the West Patio:

Two more pours next week, and two more the following week, will finish the patio at slab level.  We still have a lot of work to do to build the water features to the North, but we really need warmer weather to start laying blocks for that.

That’s the progress for this week.  I hope you enjoyed reading the report!

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