E4 Electrical Installation #1 Power Distribution, Delta and Wye Systems

Electrical Distribution 200,000 – 400,000 Volts 208/480 Volts Three Phase (3Ø) 7200 Volts Transformer Drops Voltage 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 v1.0

Power at the Pole A step-down transformer mounted to a pole can provide normal voltage directly to a building close to the pole. Sometimes the building is far from the pole. The high voltage is run underground to a transformer nearer the building. © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

1 Pole, 2 Houses, 2 Transformer Types Line Voltage 7200 Volts Tap for 7200v 7200v Primary Ground Fuse 240/120v Secondary out of transformer 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 v1.0

Transformers Following is a picture of an underground service transformer The transformer is stepping down 7200 volts to 240/120 volts. Note the safety precautions by the power company technician © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

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 v1.0

Electric Meter Meter hub on a residence © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Power out to electric panel Meter Enclosure Power In Electric Meter Power out to electric panel © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Residential Single Phase Power Following is a diagram of 120/240 volt 1 Ø power © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Common Residential 120/240v-1Ø © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Electrical Panel Inside the building is the electric panel Circuit breakers distribute the power © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Good Workmanship Counts Main Breaker Neutral Cable ties Ground Typical 1Ø Electric Panel Smooth bends in the wires Nice Job! Circuit Breakers Bus Bars © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Commercial Power – WYE Wiring Most commercial applications use the “Wye” power configuration The diagram looks like a “Y” © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Wye Hookups 120/208v-3Ø L1 L3 Wye 4-wire Schematic Diagram Wye Configuration L1 L2 L3 N N 208v 208v 120v L2 208v 120v 120v 120v 120v 120v 208v 208v 208v © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

Delta Wiring Another commercial configuration is the “Delta” Its name is derived from the Greek symbol “∆” for Delta. Delta wiring has a “high leg” when one particular power leg is used with a neutral © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

4-wire Schematic Diagram Delta Hookups 120/240v-3Ø Delta Configuration 4-wire Schematic Diagram L1 L1 L2 L3 N N L3 L2 120v 120v 208v 240v 240v 120v 240v 240v 240v 120v 240v 208v © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0

END OF Power Distribution, Delta & Wye Systems © 2005 Refrigeration Training Services - E4#1 Power Distribution, Delta & Wye Systems v1.0