Test 2 study guide - Electric Power Realtionships of 3...

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Electric Power Realtionships of 3 phase systems Voltage VL= VL over the square route of 3 VLL= Square route of 3 times VLL between two lines Single Phase System - 2 wires for 120v service - 3 wires for 120v/240v service Three Phase System - Utility company produce and deliver electricity using a 3 phase system. - 3 voltages are generated that are 120 degrees out of place with each other. - Advantages more efficient then single phase system. o Better voltage regulation o Smaller am parity for same power delivered o Longer lasting motors Y- connection, 4 wire - Each cable carries live current and line to natural voltage - In a balanced Y system ( each phase uses the same power0 the natural carries no current. Natural Conductor is smaller than line conductors. Delta Connection 3 or 4 wires Load are connected between phases voltage is line to line 3 wire has a 110 neatural 4 wire connection has a natural attached in one of the phases Balanced Power Pa= 3V l*n* IL (using line to neutral) PA= Square route of 3 times VL*L*IL (using line to line) Example: What is the power comsumed by a 3 phase motor connected to a 120/208V service and drawing 12 a of current per line. Line to natural is first number 120v Line to line is 2 nd number 208 v VLN= 120 VLL=208 Pa= 3* VL* IL = 3*120v*12a PA= 4320 VA Pa=Sq Rt of 3 * VLL*IL
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Pa= SQ 3 *208*12 4320 VA If the same motor was 1 phase instead of 3 phase, how much current would it draw for the same power of 120 V PA= V*I = 4320 va I = Pa/V = 4320Va/120v = 36 A Typical Utility System Generating Plant, Transmisson Lines, Distribution Lines, Building Service. Step Up transformer at Generating Plant, Sub Station with step down transformers,
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This note was uploaded on 04/07/2008 for the course CCEV 140 taught by Professor Aires during the Spring '08 term at Wentworth Institute of Technology.

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Test 2 study guide - Electric Power Realtionships of 3...

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