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I have a couple of basic questions on three phase generator connections. I am trying to connect a three phase machine (datasheet) as a generator to a three phase load on a breadboard, as shown:

schematic

simulate this circuit – Schematic created using CircuitLab

The physical generator has 4 wires coming out of it; three are for the phases A, B and C, while the fourth one is for frame ground. My questions are:

(1) Should the frame ground wire be connected anywhere on the breadboard?

(2) What is the purpose of frame ground?

Thank you.

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  • \$\begingroup\$ Before we go any further - 1) what kind of three-phase generator are you using - a physical alternator, with rotating metal parts? Or three sine-wave signal generators? 2) What kind of power / voltage levels are you dealing with? \$\endgroup\$ – Li-aung Yip May 14 '15 at 9:56
  • \$\begingroup\$ Its a permenant magnet synchronous machine (datasheet). The phase voltages will be sinusoidal. Power = 24 W, Current = 1.16 A. \$\endgroup\$ – Adeel May 14 '15 at 10:31
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It looks like you are using a 24VDC brushless DC motor as a generator, to stand in for a three-phase generator in some bench-top experiments.

If you are working with less than 50 volts, you should be able to operate this motor 'un grounded' without any safety concerns.

Regardless, best practice would be to earth the generator's "frame ground wire". Your electronics lab should have earth bars running around all the benches for this purpose.

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  • \$\begingroup\$ Yes, this is my personal desktop setup. If I wanted to furnish an 'earth' connection bus on the breadboard, is there a way? \$\endgroup\$ – Adeel May 14 '15 at 12:13

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