This set of Design of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Errors”.
1. What is the definition of current transformer?
a) it is used for measuring high voltage
b) it is used for measuring low voltage
c) it is used for measuring high current
d) it is used for measuring low current
View Answer
Explanation: For the measuring of high currents, the current transformer is made use of. The measured current is scaled down to lower values equivalently.
2. How many classifications are present for the current transformers?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The current transformers is divided into 2 types. They are I) measuring current transformer and II) protective current transformer.
3. What is the definition of the ideal current transformer?
a) the primary and secondary windings are in exact ratio and same phase relationship
b) the primary winding and secondary winding ratio is greater than 1 and same phase relationship
c) the primary and secondary winding ratio is lesser than 1 are in exact ratio and different phase relationship
d) the primary and secondary windings ratio is greater than 1 and different phase relationship
View Answer
Explanation: The primary and secondary winding ratio are same. The phase relationship of the windings are also same.
4. How many types of errors are present in the current transformers?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: There are 2 types of errors present in the current transformers. They are ratio error and phase angle error.
5. What is the formula of the angle between secondary induced voltage and secondary current?
a) phase angle = tan-1 *[(reactance of the secondary winding – reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)]
b) phase angle = tan-1 *[(reactance of the secondary winding – reactance of the external burden) / (resistance of the secondary winding – resistance of the external burden)]
c) phase angle = tan-1 *[(reactance of the secondary winding * reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)]
d) phase angle = tan-1 *[(reactance of the secondary winding + reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)]
View Answer
Explanation: The reactance of the secondary windings and the external burden is first calculated. Next, the resistance of the secondary windings and external burden is calculated and on substitution gives the value of the phase angle.
6. What is the formula of the phase angle of the secondary load circuit?
a) phase angle of secondary load circuit = tan-1 * (reactance of the external burden/resistance of the external burden)
b) phase angle of secondary load circuit = tan-1 * (reactance of the external burden + resistance of the external burden)
c) phase angle of secondary load circuit = tan-1 * (reactance of the external burden – resistance of the external burden)
d) phase angle of secondary load circuit = tan-1 * (reactance of the external burden * resistance of the external burden)
View Answer
Explanation: The reactance and resistance of the external burden is first calculated. Next, the value is taken tan inverse to obtain the phase angle of secondary load circuit.
7. What is the formula of the ratio error in the current transformers?
a) ratio error = turns ratio – regulation / regulation
b) ratio error = turns ratio + regulation / regulation
c) ratio error = turns ratio * regulation / regulation
d) ratio error = 1 / turns ratio * regulation
View Answer
Explanation: First the turns ratio is calculated. Next the regulation of the current transformer is obtained and on substitution gives the ratio error.
8. The ratio of active conductor section to total conductor section is called space factor.
a) true
b) false
View Answer
Explanation: The space factor is a term that is used in the design of the magnet coils. It is the ratio of the active conductor section to the total conductor section.
Sanfoundry Global Education & Learning Series – Design of Electrical Machines.
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