____-pole circuit breakers are used to connect three-phase circuits.

a. Single
b. Double
c. Three
d. Variable


c. Three

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Which of these devices is NOT used to control the airflow in an HVAC system?

A) Electric motor B) Vacuum motor C) Exciter module D) Cable

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bipolar BLDC motor is used to drive a unidirectional torque of 300 Nm. The voltage of the dc source is 400 V, k? = 1.0 Vs, and the armature resistance of the motor is 1.0 ?. Compute the modulation factor for the following cases:

a. Motor operation at 600 rpm b. Holding c. Plugging at 300 rpm in the reverse direction Also, compute the armature current in all of the above cases.

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If you wanted to monitor a large alternating current without opening the circuit you would likely use a ________

A) current-sensing inductor B) current transformer C) step-down transformer D) any of the above

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Refer to Figure P2.49 and assume R0 = 2 ?, R1 = 1 ?, R2 = 4/3 ?, R3 = 6 ?, and VS = 12 V. Use KVL and Ohm’s law to find:



Known quantities:
Schematic of the circuit shown in Figure P2.55 with resistors R0 = 2 ?, R1 = 1 ?, R2 = 4/3 ?, R3 = 6 ?, and VS = 12 V. and voltage source Vs=12V.
a. The mesh currents ia , ib, and ic.
b. The current through each resistor.

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