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traneus
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Re: I remember
traneus   2/28/2015 12:27:01 PM
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@zeeglen: I always wondered why a phase-locked-loop could not be used to perfectly synchronize the generators rather than a human manually adjustiing the frequency and phase...

Short answer: Because the human was a more reliable phase-locked loop than was an electromechanical device.

Back in the day, there were no semiconductor devices except low-power diodes. A phase-locked-loop would have had to be built with electromechanical devices (which was perfectly feasible) , with perhaps vacuum tubes to provide gain and gas tubes to provide switches.

Electric-power engineers tend to be very conservative and, until recently, came from a purely electromechanical background.

Forty years ago, using power semiconductors for electric-power rectifiers, let alone control, was novel. I remember the first generation of megawatt-level silicon rectifiers and thyristors: an entire wafer dedicated to a single device (admittedly these were one-inch wafers), in hockey-puck packages clamped between two big heatsinks. At 1000 amperes, one diode drop gets hot.

zeeglen
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Re: I remember
zeeglen   2/28/2015 10:49:41 AM
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@mhrackin The official procedure was to manually bring it within a couple of degrees of sync (lagging), then pop the '"big switch."

As a young lad working as a radar console operator on the DEW Line in the Canadian Arctic, I often got a phone call from the 'inside mechanic' that he was about to bring another diesel generator online so he could shut down another for routine maintenance.  Therefore any equipment alarms were caused by the resulting power bump, not due to an actual equipment failure.

I always wondered why a phase-locked-loop could not be used to perfectly synchronize the generators rather than a human manually adjustiing the frequency and phase...

donq_#1
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Re: I remember
donq_#1   2/27/2015 5:30:13 PM
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"there was a huge "BOOOOOM" and the entire building quaked."

Reminds me of stories I heard in the military back in the day. When another truck mounted generator needed to be added into the grid at a field location, they would have to phase it by watching a couple of lights. When the waxing and waning was in sync, the operator would throw the switch merging into the grid. Apparently, if not done correctly, as the rotor was snatched in one direction, the rest of the generator and truck it was attached to would be snatched in the other direction. The story was that it could flip the whole show on its back in the blink of an eye.

BigTech0
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Reminds me...
BigTech0   2/27/2015 4:40:29 PM
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Reminds me of Robin Scott Wilson's story, "The Big Connection" (http://www.isfdb.org/cgi-bin/title.cgi?697925) in Harry Harrison's Nova 1 anthology.  Fun!

Crusty1
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Re: I remember
Crusty1   2/27/2015 4:06:32 PM
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@mhrackin: My real question is that I assunme ther is some sort of clock drivung the logic; yet ther is no mention of any capacitors (or a crystal) in the detailed list of components used!

It's amazing how good a time base the UK AC power supply is over the long term. I have used synchronous motors in analogue clocks for years, with great time keeping except during power outages. I have also squared the AC sine wave to count cycles and drive counters to show time. Maybe this uses something like this.

Even simpler is the humble pendulum and electro magnet which ahs been used in clock movements to regulate time, by many clock makers, I have repaired a few of these and they keep excellent time for very little energy input.

mhrackin
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Re: I remember
mhrackin   2/27/2015 3:58:06 PM
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@max: ...it says that he's using the 60Hz mains frequency as his clock...."

That can be extremely accurate!  Pre-GPS, but post-formation of the power grid, US generating stations (like the one I worked in for my first job) had to maintain long-term frequuency to maybe 1ppm or better to 60 hz. There was a fair amount of equipment in place to maintain phase sync as well, because getting out of phase sync could create HUGE reactive power flows!  Back in 1961, when we had to start up a turbine "cold," the chief engineer had to manually bring the turbine into sync BEFORE it could be connected to the grid.   Our lunchroom was in a partial wing directly over the turbine room.  One day, while we were eating lunch, there was a huge "BOOOOOM" and the entire building quaked.  I jumped out and shouted "What was that?' as all the "old hands" were laughing their butts off.  My "buddy" explained that was a routine occurrence after maintenance, as the 260 MW turbine generator was  brought back on line. The official procedure was to manually bring it within a couple of degrees of sync (lagging), then pop the '"big switch."  There would be a short but very big surge, as the grid pulled the 150 ton rotor into phase lock.

Max The Magnificent
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Re: I remember
Max The Magnificent   2/27/2015 3:00:01 PM
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@mhrackin: My real question is that I assunme ther is some sort of clock drivung the logic; yet ther is no mention of any capacitors (or a crystal) in the detailed list of components used!

From what I gathered from his site -- I think it says that he's using the 60Hz mains frequency as his clock.

 

mhrackin
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Re: I remember
mhrackin   2/27/2015 2:38:47 PM
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@aubrey:  I too remember DTL.  LEDs will generally work fine with nominal 5V or 6VDC.  At that level, there's enough to work with the forward drop, and not enough to cause problems  with leakage in the reverse polarity state.  With the usual single transistor inverter following the diodes forming tha actual gate, there isn't a problem with cascading gates.  If one prefers a non-inverting structure, a complementary pair does the job with the bonus of better current drive capability.  Remember that the "T" in DTL stands for Transistor! 

My real question is that I assunme ther is some sort of clock drivung the logic; yet ther is no mention of any capacitors (or a crystal) in the detailed list of components used!

antedeluvian
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I remember
antedeluvian   2/27/2015 2:20:03 PM
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Max

I do remember how to make AND and OR gates with diodes and invert with a transistor- I still do it on occasion. But I have never used an LED as the diode. I guess you do need to consider the forward voltage drop for the logic levels further down the circuit as well as the maximum reverse voltage which can be quite low. We won't talk about switching speed.

antedeluvian
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Another artist
antedeluvian   2/27/2015 2:16:07 PM
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Max

I was once working on a job at a panel builder in London, Ontario. They had a Chinese guy (and by that I mean a guy who had come from and learned his trade in China) who would wire the panels. I have NEVER seen anyone wire so neatly and everything was in straight lines and right angles. Truly a work of art!

As an aside to that, I was told in the good old days that once a technician from British Telecomm had installed a telephone, the foreman would check the wiring with a spirit level.

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