Electrical Measurements Questions and Answers – Phase Sequence Indicator

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Phase Sequence Indicator”.

1. Phase sequence indicator gives the maximum value of phase voltages.
a) True
b) False
View Answer

Answer: a
Explanation: The phase sequence for a three phase supply indicates the order in which maximum values of phase voltages ER, EY, and EB occur. A three phase supply can be in either RYB or RBY configuration.
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2. Synchronization of A.C. supply means __________
a) different phase sequence
b) same phase sequence
c) zero phase
d) using a transformer
View Answer

Answer: b
Explanation: During synchronization, the phase sequences of any two given supplies are maintained equal. This is ensured by making use of a phase sequence indicator.

3. How many types of phase sequence indicators are there?
a) 1
b) 5
c) 2
d) 10
View Answer

Answer: c
Explanation: Generally, two types of phase sequence indicators are used. The first one is the rotating type while the second type is the static type. Usually the rotating type of phase sequence indicator is used.

4. A rotating phase sequence indicator consists of ________
a) 1 coil
b) 2 coils
c) 5 coils
d) 3 coils
View Answer

Answer: d
Explanation: A rotating type of phase sequence indicator basically consists of three coils. These are mounted at 120º to each other is space. The ends of the coils are connected to the terminals R, Y, and B respectively.
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5. The three coils are ________
a) star connected
b) delta connected
c) not connected
d) shorted
View Answer

Answer: a
Explanation: In a rotating type phase sequence indicator, the three coils are connected in the form of a star and excited by a three-phase supply.

6. Excitation of the three coils produces ________
a) a static magnetic field
b) a rotating magnetic field
c) a static electric field
d) a rotating electric field
View Answer

Answer: b
Explanation: Aluminum disc is mounted on the top of the three coils. A rotating magnetic field is produced when the three coils are excited by a supply of three phase. As a result e.m.f with eddy current effects are induced in the coils.

7. Eddy e.m.f produces a torque.
a) True
b) False
View Answer

Answer: a
Explanation: A rotating magnetic field is produced when the three coils are excited by a supply of three phase. As a result, eddy e.m.f circulates in the disc. A torque is produced as a result of the interaction between the eddy currents and the rotating magnetic field.
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8. Disc rotation is determined by ________
a) the supply voltage
b) an arrow
c) the turns ratio
d) the load current
View Answer

Answer: b
Explanation: Direction of rotation of the disc is determined by making use of an arrow that is marked on the disc. The phase sequence of the supply voltage is same as that mentioned on the terminals of the meter provided disc rotates in the same direction as the arrow head.

Sanfoundry Global Education & Learning Series – Electrical Measurements.

To practice all areas of Electrical Measurements, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Instagram | Facebook | Twitter