EASA module 4 Electronic Fundamentals mcq 6

If two of the stator leads are cross connected in a control synchro system, a 25o clockwise rotation of the input rotor would result in the output rotor
a) moving 25o clockwise
Ans b) moving 25o anticlockwise
c) moving 180o to rectify the defect
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Damping in a servomechanism is easier to apply if
Ans a) the mechanism is light and has low inertia
b) the mechanism is heavy and has high inertia
c) the mechanism is light and has high inertia
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Reverse bias
a) lowers the potential barrier
Ans b) raises the potential barrier
c) greatly increases the majority carrier current
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If the electrical connections to the feedback generator in a control synchro system were disconnected, the
a) motor would run in the wrong direction
b) input signal to the amplifier would reduce
Ans c) system would tend to oscillate
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An increase in servo amplifier gain
a) reduces the speed of the system
Ans b) increases system response
c) reduces tendency to hunt
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In a control synchro the stator current ceases to flow when the
a) CT rotor is at null
b) two rotors are aligned
Ans c) power is removed
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The term 'velocity lag' refers to a
a) speed error
Ans b) position error
c) acceleration error
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The rotor of an AC tachogenerator
a) has skewed slots
Ans b) has a copper, brass or aluminium cylinder
c) rotates at constant speed
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A servo system with transient negative velocity feedback
Ans a) is damped with little velocity lag
b) is damped with high velocity lag
c) is underdamped with high velocity lag
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To reverse the direction of rotation of a two phase induction motor
Ans a) reverse the polarity of the control phase
b) reverse the polarity of both the control phase and reference phase
c) shift the reference by 90o
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In a rate servo (speed control) the signal into the servo amplifier is
a) input voltage plus tachogenerator output
Ans b) input voltage minus tachogenerator output
c) input voltage plus position feedback voltage
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Loss of DC to a servo amplifier causes the motor to
a) run continuously
Ans b) stop
c) reverse
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A reduction from the optimum setting of the velocity feedback in a servo loop could cause
a) low servo gain
Ans b) instability
c) slow response
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In a torque synchro system, the power supply is connected to
a) the rotor windings of the transmitter only
Ans b) the rotor windings of both the transmitter and receiver
c) the stator windings of the transmitter
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The phase difference between the supplies of a two phase induction motor is
a) 180o
Ans b) 90o
c) 0o
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To reduce overshoot errors in a synchro
a) the system will have position feedback
Ans b) the system will have velocity feedback
c) the gain of the amplifier is increased
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A synchro transformer is used to
Ans a) derive an error voltage from a synchro transmitter signal and a shaft position
b) obtain a 26 volt AC reference
c) add the output of two synchro transmitters
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This is a diagram of a
Ans a) differentiator
b) integrator
c) adder
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Reversal of the complete power to a torque synchro system will
Ans a) have no effect
b) cause reverse rotation of the receiver rotor
c) displace the receiver rotor by 180o
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The power supply to a torque synchro system is
Ans a) AC
b) DC
c) AC or DC
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This symbol is
a) an LED
b) a laser diode
Ans c) a photodiode
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When a positive voltage is applied to the base of a normally biased n-p-n common emitter amplifier
a) the emitter current decreases
Ans b) the collector voltage goes less positive
c) the base current decreases
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An amplifier current gain will be slightly less than 1, but its voltage gain will be high, if it is connected in the
Ans a) common base configuration
b) common emitter configuration
c) common collector configuration
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An open loop system is one which has
Ans a) no direct feedback loop
b) rate feedback loop
c) position feedback only
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Mechanical friction in a servo results in
a) reduced gain
Ans b) increased damping
c) increased inertia
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