Transcript E2 Subject1
E4 Electrical Installation #1 Power Distribution Electrical Distribution 200,000 – 400,000 Volts 208/480 Volts Three Phase (3Ø) 7200 Volts Transformer Drops Voltage 7200 Volts Substation Transformers Drop Voltage To 7200 Volts 120/240 Volts Single Phase (1Ø) © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 2 Power at the Pole • A step-down transformer mounted to a pole can provide normal voltage directly to a building close to the pole • When the building is far from the pole, the high voltage is run underground to a transformer near the building © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 3 1 Pole, 2 Houses, 2 Transformer Types Line Voltage 7200 Volts Tap for 7200v 7200v Primary Ground Fuse 120/240v Secondary out of transformer 120/240v underground to electric panel in House #1 7200 Volts underground to transformer at House #2 © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 4 Transformers • Following is a picture of an underground service transformer – The transformer is stepping down 7200 volts to 120/240 volts – Take note of the safety precautions practiced by the power company technician © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 5 Underground Service Transformer Eye Protection Rubber Arm Shields Thick Rubber Gloves Transformer 7200v Primary 120/240v Secondary © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 6 Electric Meter • Meter hub on a residence © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 7 Meter Enclosure Power In Electric Meter Power out to electric panel © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 8 Residential Single Phase Power • Following is a diagram of 120/240 volt 1Ø power © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 9 Common Residential 120/240v-1Ø L1 L2 240v N 120v 120v © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 10 Electric Panel • Inside the building is the electric panel • Circuit breakers distribute the power © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 11 Good Workmanship Counts Main Breaker Neutral Cable ties Ground Smooth bends in the wires Typical 1Ø Electric Panel Circuit Breakers Bus Bars © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 12 © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.2 13