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Lighting & Electrical
Lighting system causes buzz/hum in the circuit breaker panels
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<blockquote data-quote="Mike Sokol" data-source="post: 58942" data-attributes="member: 1989"><p>Re: Lighting system causes buzz/hum in the circuit breaker panels</p><p></p><p></p><p></p><p>Ah yes.... Delta vs. Wye 3-phase wiring. There's actually very little Delta 3-phase in buildings anymore. It's now reserved for power transmission over high-tension lines. Most industrial 3-phase is WYE connected with a neutral and 480/277 volts or 208/120 volts. However, there's something really interesting and scary that happens with 3-phase Wye connections that have unbalanced current draw that includes a lot of harmonics (think lighting dimmer packs). Triplen Harmonic Currents. Look up Triplen Harmonics at <a href="http://www.hersheyenergy.com/harmonics.html" target="_blank">Harmonics, Triplen Harmonics, Adjustable Speed Drive, Power Quality</a></p><p></p><p>Three phase WYE transformers don't like light dimmer packs because the odd-order harmonics from the dimmers build up on the neutral leg since the hot legs are separated by 120 degrees of phase shift. This Triplen harmonic current can sometimes be as much as 400% to 700% of the single load amperage. So if you're drawing 100 amps on a single leg of a 3-phase panel with Triac dimmers, there can be 400 to 700 amperes on the neutral bus between the transformers themselves. That's why the neutral bus in 3-phase lighting installations need to be oversized or it will burn up at relatively small dimmer pack loads. I've also got to believe that these 3rd harmonic Triplen Currents will do all sorts of mischief if connected to a sound system, which could be the source of your buzzing. Any there's probably enough harmonic currents there to actually make a panel physically buzz. </p><p></p><p>There was also a hybrid Delta/WYE transformer variation of 3-phase power from the 50's/60's called a High Leg (or Wild/Red Leg) Delta connection. See <a href="http://en.wikipedia.org/wiki/High-leg_delta" target="_blank">High-leg delta - Wikipedia, the free encyclopedia</a> for an overview. This was done as a way to save transformers on industrial buildings since you can pull 120 volts from Neutral to two of the low busses, and 240-volts between the two low busses, but the 3rd High-Leg measures 208 volts from the Neutral. Be very careful around this type of panel as it's a good way to blow up 120 volt gear, especially lights.</p></blockquote><p></p>
[QUOTE="Mike Sokol, post: 58942, member: 1989"] Re: Lighting system causes buzz/hum in the circuit breaker panels Ah yes.... Delta vs. Wye 3-phase wiring. There's actually very little Delta 3-phase in buildings anymore. It's now reserved for power transmission over high-tension lines. Most industrial 3-phase is WYE connected with a neutral and 480/277 volts or 208/120 volts. However, there's something really interesting and scary that happens with 3-phase Wye connections that have unbalanced current draw that includes a lot of harmonics (think lighting dimmer packs). Triplen Harmonic Currents. Look up Triplen Harmonics at [URL="http://www.hersheyenergy.com/harmonics.html"]Harmonics, Triplen Harmonics, Adjustable Speed Drive, Power Quality[/URL] Three phase WYE transformers don't like light dimmer packs because the odd-order harmonics from the dimmers build up on the neutral leg since the hot legs are separated by 120 degrees of phase shift. This Triplen harmonic current can sometimes be as much as 400% to 700% of the single load amperage. So if you're drawing 100 amps on a single leg of a 3-phase panel with Triac dimmers, there can be 400 to 700 amperes on the neutral bus between the transformers themselves. That's why the neutral bus in 3-phase lighting installations need to be oversized or it will burn up at relatively small dimmer pack loads. I've also got to believe that these 3rd harmonic Triplen Currents will do all sorts of mischief if connected to a sound system, which could be the source of your buzzing. Any there's probably enough harmonic currents there to actually make a panel physically buzz. There was also a hybrid Delta/WYE transformer variation of 3-phase power from the 50's/60's called a High Leg (or Wild/Red Leg) Delta connection. See [URL="http://en.wikipedia.org/wiki/High-leg_delta"]High-leg delta - Wikipedia, the free encyclopedia[/URL] for an overview. This was done as a way to save transformers on industrial buildings since you can pull 120 volts from Neutral to two of the low busses, and 240-volts between the two low busses, but the 3rd High-Leg measures 208 volts from the Neutral. Be very careful around this type of panel as it's a good way to blow up 120 volt gear, especially lights. [/QUOTE]
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