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I'm reading the book Basic Electricity from Milton Gussow and there's a problem that is driving me crazy, I'm not able to get the result. Can anyone provide me with a guideline to resolve it?

This is the problem:enter image description here

Thanks.

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This needs phasors because your motors take a little inductive currents and the lamps act as resistors. The motors are Y-loads but the lamps are a D-load, which cause harmful interline currents. Fortunately the lamp banks are identical, so the equivalent resistive Y-load exists. Find it and add the single line currents as phasors. Note that delta to Y transform is not a must, it only makes the number of needed phasors a little smaller.

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  • \$\begingroup\$ I'm not sure what you mean, why the Y-loads and the D-loads? I'm trying to do this: Motor 1: 15A * 0.8 + Motor 2: 20A * 0.95 + 24.5A, after that I get the inductive currents of the motors and get the resulting current with: amp = sqrt(x^2+y^2). \$\endgroup\$ – Ricky2 Aug 12 '17 at 21:19
  • \$\begingroup\$ @Ricky2 lamp banks are between the lines. That is delta. Y is 3 loads, one end of each is at a line, the other ends are all together. Instead of 24.5A you should use squareroot (3)*24.5A because that is the effective one line current. \$\endgroup\$ – user287001 Aug 12 '17 at 22:30

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