Flashcards in Week 2 Deck (10)
Provide three advantages that three-phase systems have over single-phase systems.
Increase in power capability
Less pulsating on rotating generators and motors
Generators, transformers, and motors are smaller and less expensive
How far apart are the three coils of a generator from one another?
How many times does the voltage fall to zero in one cycle?
If the system voltage is 12,470 volts, what would the coil voltage be in a WYE configuration?
If the phase current in a WYE system is 40A, what is the coil current?
If the coil voltage in a DELTA system is 12,000 volts, what is the system voltage?
Why could linemen work barehanded on the older DELTA systems back in the day?
Because there was no ground or neutral reference. If there was nothing touching the other phases on the circuit, like a tree limb or another lineman, then there was no short circuit.
Why is it hard to tell the difference between a DELTA and an ungrounded WYE in the field?
Because neither system has a system neutral.
What is meant by “phase sequence”?
Phase sequence is the direction a motor will spin, based on how it is connected to the system. If the sequence is unchanged, the motor will spin the same direction as the generator.