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Today’s automation industry quiz question comes from ISA’s course, Electrical Controls for the Control Systems Technician (TI23). This course focuses on electrical controls that are Three-Phase Powerfrequently overlooked in a formal training program. It is geared toward any level technician who wants a thorough review of electrical process concepts to reinforce their knowledge of basic electricity and develop skills required to install and maintain electrical control devices. The next class starts Dec. 7.

Discount Alert: Register today to take advantage of a 40% special discount for the pilot offering of the electrical controls course. Click this link to view the special offer. Registration closes Nov. 23.


The phase difference between each phase in a three-phase system is which of the following?

a) 180 degrees
b) 120 degrees
c) 270 degrees
d) 90 degrees
e) none of the above


Click Here to Reveal the Answer

Here’s the answer to today’s quiz from the instructor for ISA’s December course offering, Electrical Controls for the Control Systems Technician (TI23).

The three phases of three-phase power are electrically separated by 120 degrees. In the case of 480 volt three-phase the voltage is approximately 477 VAC across any two legs when connected in a “Y” configuration. Three-phase power provides more constant power due to a constant differential.

The correct answer is B.

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