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// Example 5.14
// Determine (a) Percent voltage unbalance (b) Expected approximate temp. rise
// if operating at rated load in a 40 deg ambient (c) Expected insulation life
// (d) Required derating of motor to prevent shortening isulation life.
// Page No. 211
clc;
clear;
close;
// Given data
VL1=460; // Line voltage 1
VL2=455; // Line voltage 2
VL3=440; // Line voltage 3
Trated=110; // Rated temp. (from table 5.8)
hp=30; // Motor horsepower
// (a) Percent voltage unbalance
Vavg=(VL1+VL2+VL3)/3; // Average line voltage
VD1=abs(VL1-Vavg); // Voltage deviation from the average
VD2=abs(VL2-Vavg);
VD3=abs(VL3-Vavg);
VD=[VD1 VD2 VD3];
VDMax=max(VD); // Choose maximum value of voltage deviation
PerUBV=(VDMax/Vavg)*100;
// (b) Expected approximate temp. rise if operating at rated load in a 40 deg
PerDeltaT=2*PerUBV^2; // Percent change in temp.
Tubv=Trated*(1+(PerDeltaT/100));
// (c) Expected insulation life
DeltaT=Tubv-Trated; // Percent increase in motor temp.
RL=1/(2^(DeltaT/10)); // Relative life on insulation
EL=RL*20;
// (d) Required derating of motor to prevent shortening isulation life
ReqDer=hp*0.92;
// Display result on command window
printf("\n Percent voltage unbalance = %0.2f ",PerUBV);
printf("\n Expected approximate temperature rise = %0.0f deg C",Tubv);
printf("\n Expected insulation life = %0.1f years",EL);
printf("\n Required derating of motor = %0.1f hp",ReqDer);
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