4 ms·

I worked at a television station years back that was designed in such a way that the lights going up the tower were powered by the separate phases of three phas

by skinwill 11mo ago

I worked at a television station years back that was designed in such a way that the lights going up the tower were powered by the separate phases of three phase AC with the one at the top powered from all three combined. This was pretty normal but what the engineer had done was rotate them at every level so that if a phase was dropped you could count the lights and quickly see from a distance that the power wasn't right. 4 lights was good, 3 meant you dropped a phase, and so on. I thought it was a pretty clever way of keeping light on all sides of the tower while being able to tell from a distance that a phase was out.

butlike 11mo ago
Fascinating
- dotancohen 11mo ago
  Phascinating I couldn't help myself, downvote at will.
  - deleted 11mo ago
    [deleted]
xenadu02 11mo ago
This is best practice for anyone who uses three phase power. A machine shop should connect 1/3 of their lights to each phase so it is immediately obvious if a phase gets dropped. Lots of equipment will suffer on two of three phases but with lower performance or even damage.
- quickthrowman 11mo ago
  > This is best practice for anyone who uses three phase power. No, it’s not. It’s a neat trick that visually reveals when the utility drops a phase, but there are better ways to handle avoiding equipment damage. Best practice is to use phase monitoring relays that can de-energize a motor when a phase is dropped/reversed to prevent damage. The trip time is adjustable and it’s more reliable than manually hitting an e-stop. It also won’t let a motor with incorrect phasing start up either. You see phase loss relays on a lot of compressor motors and other large motors. Here’s a flyer for an Eaton product: https://www.eaton.com/content/dam/eaton/products/industrialcontrols-drives-automation-sensors/overload-relays/d65-monitoring-relays-pa049001en.pdf https://www.eaton.com/content/dam/eaton/products/industrialc...
- genter 11mo ago
  I was told that you want lights on all 3 phases so that you can see spinning things spin. If the lights are on single phase, they will dim 120 times a second, and the strobe effect can cause spinning things to appear stationary. With 3 phase, at least 1/3 of the lights are lit all the time.
  - marcosdumay 11mo ago
    That's a valid reason too. In an industrial environment full of rotating machines, thinking something is stationary because it's on the grid's natural frequency can be lethal. It's way less of a problem with modern machinery, and leds will blink in uncorrelated phases in a frequency that is different from the grid's anyway.
    - wtallis 11mo ago
      For residential lighting running off a single-phase supply, there are some annoying LED bulbs with simple half-wave rectification that strobe at the grid frequency with less than a 50% duty cycle (often seen with bulbs emulating vintage exposed-filament bulbs with no frosted glass). It would be interesting to see how much less annoying that kind of flicker is when you have a three-phase supply to a light fixture, so that at least one set of LEDs was illuminated at all times.
      - quickthrowman 11mo ago
        There are no light fixtures that use three-phase power. At least that’s my belief, as I’ve never heard of one or seen one and I’ve been working in the electrical industry for almost a decade. You could theoretically arrange three lampholders like a delta or wye transformer [0] and connect a phase to each one and all three lamps will be lit, but the lampholders will be energized, so make sure to wear voltage-rated gloves when changing out the lamps ;) This is how three-phase resistive heaters are wired, the drop in ampacity and large resistive heating loads make it worth using three phase since ampacity is 1.73 times lower than it would be on a three-phase circuit than it would be at the same voltage as a single-phase circuit. In the US, there are 208V single-phase and 480V single-phase lights that use two of the three phases. In practice, indoor lighting is either 277V (line to neutral on a 480V service) or 120V (line to neutral on a 208V service). Most commercial LED fixtures can use any voltage between 120V to 277V single-phase. 480V single phase is used for some pole lighting with long runs of conductors to handle voltage drop. Anything over 277V has to be elevated at least 22 feet off the ground per the NEC. [0] https://en.wikipedia.org/wiki/Delta–wye_transformer https://en.wikipedia.org/wiki/Delta–wye_transformer
- MisterTea 11mo ago
  At work we run a lot of machinery with motors and its obvious when phase loss happens. From my office I can tell if the lights go out/dim and the usual shop "hum" becomes a buzzing grunt that is immediately identifiable. Older machines have to be manually powered down but the machines I rebuilt have phase loss protection in the PLC thanks to a power monitoring terminal in the IO (Beckhoff EL3453.) Since the PLC is on 24V DC I have a capacitor backup module fronted by a 24V PSU that takes the 480V three phase power which tolerates a phase loss. The machine safely stops the process and shuts down the pumps and any other AC loads, then waits to be manually powered off as the PSU and DC side doesn't care.
geerlingguy 11mo ago
Clever! I know I talked to the folks at Masterclock in St. Louis recently about one of their clock displays; they intentionally default the separators to flash if the clock is not synced to NTP, and then they go solid once the connection is established. It's a quick way to know if something is down, using context clues that are already there to begin with!
- skinwill 11mo ago
  Jeff, it's very cool to hear from you as I have enjoyed your videos for some time. I would like to make one request though. Next time you do a project like "How I almost broke MrBeast's Ages 1-100 video" that involves setting up interactive electronics for an event, you should really call me. I managed interactive technology deployments for the automotive marketing industry for over a decade. It's a niche that has unique challenges which you fell face first into. I would be happy to help make things go much smoother should you ever do something similar. Proof: https://imgur.com/a/5z5JrwT https://imgur.com/a/5z5JrwT I'm also on Reddit, same screen name if you want to dm me there.

butlike 11mo ago

Fascinating

dotancohen 11mo ago
Phascinating I couldn't help myself, downvote at will.
- deleted 11mo ago
  [deleted]

xenadu02 11mo ago

This is best practice for anyone who uses three phase power. A machine shop should connect 1/3 of their lights to each phase so it is immediately obvious if a phase gets dropped. Lots of equipment will suffer on two of three phases but with lower performance or even damage.

quickthrowman 11mo ago
> This is best practice for anyone who uses three phase power. No, it’s not. It’s a neat trick that visually reveals when the utility drops a phase, but there are better ways to handle avoiding equipment damage. Best practice is to use phase monitoring relays that can de-energize a motor when a phase is dropped/reversed to prevent damage. The trip time is adjustable and it’s more reliable than manually hitting an e-stop. It also won’t let a motor with incorrect phasing start up either. You see phase loss relays on a lot of compressor motors and other large motors. Here’s a flyer for an Eaton product: https://www.eaton.com/content/dam/eaton/products/industrialcontrols-drives-automation-sensors/overload-relays/d65-monitoring-relays-pa049001en.pdf https://www.eaton.com/content/dam/eaton/products/industrialc...
genter 11mo ago
I was told that you want lights on all 3 phases so that you can see spinning things spin. If the lights are on single phase, they will dim 120 times a second, and the strobe effect can cause spinning things to appear stationary. With 3 phase, at least 1/3 of the lights are lit all the time.
- marcosdumay 11mo ago
  That's a valid reason too. In an industrial environment full of rotating machines, thinking something is stationary because it's on the grid's natural frequency can be lethal. It's way less of a problem with modern machinery, and leds will blink in uncorrelated phases in a frequency that is different from the grid's anyway.
  - wtallis 11mo ago
    For residential lighting running off a single-phase supply, there are some annoying LED bulbs with simple half-wave rectification that strobe at the grid frequency with less than a 50% duty cycle (often seen with bulbs emulating vintage exposed-filament bulbs with no frosted glass). It would be interesting to see how much less annoying that kind of flicker is when you have a three-phase supply to a light fixture, so that at least one set of LEDs was illuminated at all times.
    - quickthrowman 11mo ago
      There are no light fixtures that use three-phase power. At least that’s my belief, as I’ve never heard of one or seen one and I’ve been working in the electrical industry for almost a decade. You could theoretically arrange three lampholders like a delta or wye transformer [0] and connect a phase to each one and all three lamps will be lit, but the lampholders will be energized, so make sure to wear voltage-rated gloves when changing out the lamps ;) This is how three-phase resistive heaters are wired, the drop in ampacity and large resistive heating loads make it worth using three phase since ampacity is 1.73 times lower than it would be on a three-phase circuit than it would be at the same voltage as a single-phase circuit. In the US, there are 208V single-phase and 480V single-phase lights that use two of the three phases. In practice, indoor lighting is either 277V (line to neutral on a 480V service) or 120V (line to neutral on a 208V service). Most commercial LED fixtures can use any voltage between 120V to 277V single-phase. 480V single phase is used for some pole lighting with long runs of conductors to handle voltage drop. Anything over 277V has to be elevated at least 22 feet off the ground per the NEC. [0] https://en.wikipedia.org/wiki/Delta–wye_transformer https://en.wikipedia.org/wiki/Delta–wye_transformer
MisterTea 11mo ago
At work we run a lot of machinery with motors and its obvious when phase loss happens. From my office I can tell if the lights go out/dim and the usual shop "hum" becomes a buzzing grunt that is immediately identifiable. Older machines have to be manually powered down but the machines I rebuilt have phase loss protection in the PLC thanks to a power monitoring terminal in the IO (Beckhoff EL3453.) Since the PLC is on 24V DC I have a capacitor backup module fronted by a 24V PSU that takes the 480V three phase power which tolerates a phase loss. The machine safely stops the process and shuts down the pumps and any other AC loads, then waits to be manually powered off as the PSU and DC side doesn't care.

geerlingguy 11mo ago

Clever! I know I talked to the folks at Masterclock in St. Louis recently about one of their clock displays; they intentionally default the separators to flash if the clock is not synced to NTP, and then they go solid once the connection is established. It's a quick way to know if something is down, using context clues that are already there to begin with!

skinwill 11mo ago
Jeff, it's very cool to hear from you as I have enjoyed your videos for some time. I would like to make one request though. Next time you do a project like "How I almost broke MrBeast's Ages 1-100 video" that involves setting up interactive electronics for an event, you should really call me. I managed interactive technology deployments for the automotive marketing industry for over a decade. It's a niche that has unique challenges which you fell face first into. I would be happy to help make things go much smoother should you ever do something similar. Proof: https://imgur.com/a/5z5JrwT https://imgur.com/a/5z5JrwT I'm also on Reddit, same screen name if you want to dm me there.