GE ballast for 175 watt H39/H22 Mercury lamp. We call these IL (independent lighting) transformers. This one was used in a 6.6 amp arc circuit (series street light circuit). It's rated for up to 10500V.



Same as above



The big can on the pole is an RO (regulated output) transformer. The small can above it is an oil switch. The disconnect to the right, feeding the oil switch, is open and tagged. This is no longer in use. The primary of this RO is 12000V. It's in our 20.8KV system, phase to ground or star. This RO puts out a constant 6.6amps and the voltage varies by the number of lights on the series circuit. It did this with a movable core and a counter balance. If the arc circuit is opened up the voltage goes to the maximum which could be just over 5000 volts on this one.



Same as above



Same as above



6.6 amp lamp from arc circuit


If this light burns out, a wafer between those two prongs, that insulates during normal operation, will burn through when the RO goes to maximum voltage, closing the arc circuit back in. These wafers were referred to as onion skins.






Delta Delta 120/240V



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Wye Delta 120/240V



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Open-Wye Open-Delta 120/240V




Delta Wye 120/208V



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Wye Wye 120/208V



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Delta Wye 277/480V




Wye Wye 277/480V



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Scott 3 wire



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Scott 4 wire



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Scott 5 wire