45 - In order to connect a synchronous generator to the main system, it is necessary to have the following conditions:

Same voltage value, same frequency values, voltage of the generator in phase with voltages of the main

Same voltage values, synchronous reactance equal to the impedance of the line, voltage of the generator orthogonal with the voltage of the main

Excitation current equal to zero, same frequency values, voltages of the generator in phase with voltages of the main

47 - The following equation shows the mechanical characteristic of: $$T=\frac{K_aφV}{R_a}-\frac{K_a^2φ^2ω}{R_a}$$

DC motor with separated excitation

DC motor with series excitation

Q. 13 THE MAIN DRAWBACKS OF A PWM INVERTER ARE?

b) Increase of the iron losses and higher leakage currents due to dv/dt

a) Increase of the torque ripple

c) Increase of the joule losses

14. CONSIDERING THE PARALLEL OF TWO TRANSFORMERS, IN ORDER TO HAVE THE SECONDARY CURRENTS PROPORTIONAL TO THE RATED POWER OF THE TRANSFORMERS IT'S NECESSARY TO

b) have the same short circuit voltage

a) have the same short circuit power

c) have the same short circuit power factor

Q 15. IN A PWM INVERTER THE AMPLITUDE OF THE OUTPUT VOLTAGE CAN BE MODIFIED CHANGING

b) The amplitude of modulating waveforms

a) the frequency of the modulating waveform

17. CONSIDERING THE PARALLEL OF TWO TRANSFORMERS, IN ORDER TO HAVE THE MINIMUM SECONDARY CURRENTS OF THE TWO TRANSFORMERS, IS IT NECESSARY TO:

c) have the same short circuit power factor

a) have the same short circuit power

b) have the same short circuit voltage

Q 18. THE FOLLOWING EQUATIONS SHOWS THE MECHANICAL CHARACTERISTIC OF $$T=\frac{V^2}{\left(R_t\ +K_t\ w\right)^2}$$

a) motor with series excitation

b) DC motor with separated excitation

Q. 19- USING THE TRANSFORMATION MATRIX WITH AN ANGLE EQUAL TO ΩT, ON TWO ORTHOGONAL SINUSOIDAL WAVEFORMS WITH PULSATION Ω, THE RESULT IS:

b) A rotation of 90° of the two sinusoidal waveforms

c) A single sinusoidal waveform

Q. 20- IN A SPEED DRIVE, THE FLUX WEAKENING REGULATION CAN BE DONE

c) For loads with quadratic torque characteristic with speed

Q. 22- THE FOLLOWING EQUATIONS REPRESENT $$M_{AB}=\ -\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta\ -120°\right)$$ $$M_{BC}=M_{CB}\ =-\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta\ \right)$$ $$M_{AC}=M_{CA}\ =-\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta-240°\ \right)$$

c) The mutual inductances between the stator windings of an anisotropic synchronous machine

a) The mutual inductances between the stator windings of an induction motor

b) The mutual inductances between the stator and the rotor of an induction motor

Q. 23- THE FOLLOWING EQUATIONS REPRESENTS

a) the mutual inductance between the stator and the rotor of an induction motor

b) the mutual inductance between the stator windings of an induction motor

c) The mutual inductances between the stator and the rotor of a synchronous machine

52 - WHAT IS THE SPEED REGULATION SHOWN IN THE FOLLOWING FIGURE?

Constant voltage/frequency regulation

53 - THE FOLLOWING EQUATIONS REPRESENTS

The stator self inductance of an anisotropic synchronous machine

The stator self inductances of an inductor motor

The self inductances of the stator and the rotor of DC Motor with series excitation

85. IN AN INDUCTION MOTOR, IN ORDER TO INCREASE THE PEAK TORQUE IT IS NECESSARY

Decrease the leakage inductances

Increase the leakage inductances

86. RESOLVER PRODUCES:

Two signals to the sine and cosine of a mechanical angle

A signal proportional to the mechanical speed

A signal proportional to a mechanical angle

88. GIVEN THE FOLLOWING CHARACTERISTIC, IT IS

DC motor with permanent magnet excitation

89. IN AN INDUCTION MOTOR WITH ONE OPEN LOOP SPEED REGULATION, THE CURRENT IS LIMITED USING

Acceleration and deceleration ramp

90. IN A DC MOTOR THE REDUCTION OF THE EXCITATION FLUX PRODUCES

Increase of the stator iron losses

91. IN A DC MOTOR THE REDUCTION OF THE EXCITATION FLUX PRODUCES

Increase of the stator iron losses

93. Non c'era scritta la domanda ma immagino sia associare questa caratteristica meccanica alla relativa macchina

DC motor with series excitation

DC motor with permanent magnet excitation

1. A single-phase sinusoidal distribution of conductor supplied with a sinusoidal current produce

a sinusoidal oscillating unidirectional magnetic field

two counter rotating magnetic fields

a constant unidirectional magnetic field

2 In order to reduce the eddy current losses in ferromagnetic cores, what is the used technology?

Adding silicon in the iron alloy

3 - In an induction motor is it necessary that

The stator and rotor number of poles must be equal

The stator and rotor number of phases must be equal

Both stator and rotor number of phases and poles must be equal

4 - The control of a sinusoidal brushless is based on

An open loop stator current control

5 - Two inductor motors have the same rated power. What is the biggest one?

The motor with higher number of poles

The motor with the lower number of poles

6 - In a six-step inverter, the DC bus voltage

Varies with the load current depending on the induction motor load

7 - The specific iron losses represent

The total iron losses in watt per kg of a ferromagnetic material

The hysteresis losses of a ferromagnetic material

The eddy current losses of a ferromagnetic material

9 - The following matrix represents

The mutual inductance between the stator and the rotor of an induction motor

The stator and rotor mutual inductance of a DC motor with separate excitatation

The mutual induc. between the stator and the rotor of a synchronous machine

10 - The no load test of an induction motor allows to determine

The iron losses and the mechanical losses

11 - The synchronous reactance of a synchronous generator takes into account

The effects of magneto-motive forces produced by stator currents

The non-linearity of stator and rotor lamination

The voltage drops due to stator and rotor currents

12 - The speed regulation of a permanent magnet DC motor can be done

With both voltage and flux regulation

95 - In a DC motor supplied at constant voltage, an increase of the load torque produces:

Increase of the armature joule losses

Reduction of the armature joule losses

Increase of the excitation winding joule losses

96 - A DC motor with series excitation can work:

In the first and fourth quadrant

25 - THE VECTOR GROUP OF A THREE-PHASE TRANSFORMER IS DEFINED AS

The angle between primary and secondary phase voltage system divided by 30

The angle between the primary and secondary line voltage system

The angle between the primary and secondary phase voltage system

26. - THE THEORY OF A TRAPEZOIDAL BRUSHLESS IS BASED ON

rotating space vectors quantities for the stator and scalar quantities for the rotor

rotating space vector quantities

27. WHAT ARE THE CONDITIONS FOR A CORRECT PARALLEL CONNECTION OF TWO SINGLE PHASE TRANSFORMERS?

Same turn ratio, connection of the corresponding terminals, same short circuit voltage, same short circuit power factor

Same transformation ratio, same vector group, same short circuit voltage, same short circuit power factor

Same transformation ratio, same vector group, same short circuit voltage, same no-load current

29. - FOR AN INDUCTION MOTOR, A SPEED REGULATION IN THE FLUX WEAKENING REGION CAN BE DONE

with a frequency regulation at constant voltage

with a voltage and frequency regulation

with a voltage regulation at constant frequency

EM 1-121

Authored by Davide Anfosso

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University

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121 questions

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MULTIPLE CHOICE QUESTION

5 mins • 1 pt

37 - The control of a trapezoidal brushless is based on:

An open loop stator control

A scalar control

A vector control using dq axis reference frame

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

38 - In DC motor in steady state conditions, the absorbed current depends on:

The motor typology

The voltage supply

The load torque

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

39 - What is the right equation of the reactive power produced by a synchronous generator:

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

40 - What is the starting torque equation of an induction motor in steady state conditions?

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

41 - What are the right electrical equations of synchronous machines in transient conditions?

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

42 - In a PWM inverter the DC bus voltage is:

Variable with the output frequency

Depending on the induction motor load

Constant with the output frequency

MULTIPLE CHOICE QUESTION

5 mins • 1 pt

43 - What is the torque equation of an induction motor in transient conditions?

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EM 1-121

37 - The control of a trapezoidal brushless is based on:

38 - In DC motor in steady state conditions, the absorbed current depends on:

39 - What is the right equation of the reactive power produced by a synchronous generator:

40 - What is the starting torque equation of an induction motor in steady state conditions?

41 - What are the right electrical equations of synchronous machines in transient conditions?

42 - In a PWM inverter the DC bus voltage is:

43 - What is the torque equation of an induction motor in transient conditions?

44 - What is the equation of a DC motor in transient condition?

45 - In order to connect a synchronous generator to the main system, it is necessary to have the following conditions:

46 - What is the right equation of a rotating magnetic field produced by a three phase system:

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