**81. Armature reaction mmf and leakage reactance of a synchronous machine are determined by**

- open-circuit and short-circuit tests
- open-circuit and zero power factor tests
- open-circuit test only
- zero power factor test only

**82. Which one of the following methods would give higher than actual value of regulation of an alternator?**

- ZPF method
- MMF method
- EMF method
- ASA method

**83. Which one of the following methods gives more accurate result for determination of voltage regulation of an alternator?**

- MMF Method
- Synchronous Impedance method
- Potier triangle method
- ASA method

**84. Slip test is performed to determine**

- slip
- direct-axis reactance and quadrature-axis reactance
- positive sequence reactance and negative sequence reactance
- sub-transient reactance

**85. For maximum current during slip test on a synchronous machine, the armature mmf aligns along**

- d-axis
- q-axis
- 45 degrees to d-axis
- 45 degrees to q-axis

**86. In which one of the following is reluctance power developed?**

- salient pole alternator
- non-salient pole alternator
- squirrel cage induction motor
- transformer

**87. Which is the value of load angle when the power output of a salient pole synchronous generator is maximum?**

- 0 degree
- 45 degree
- 90 degree
- none of the above

**88. Higher synchronous reactance is preferred in the present day alternators, because one can have**

- reduced sub-transient currents
- reduced harmonic currents
- reduced transient currents
- higher voltage regulation with load

**89. When a 3-phase alternator is suddenly short-circuited at its terminals, the initial value of short-circuit current is limited by which one of the following**

- subtransient reactance
- transient reactance
- synchronous reactance
- Sum of all the above

**90. An alternator with higher value of Short Circuit Ratio has**

- poor voltage regulation and lower stability limit
- better voltage regulation and higher stability limit
- poor voltage regulation and higher stability limit
- better voltage regulation and low stability limit