Free Printable EM 1-121

1.

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

a)

An open loop stator control

b)

A scalar control

c)

A vector control using dq axis reference frame

2.

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

a)

The motor typology

b)

The voltage supply

c)

The load torque

3.

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

a)

$Q_e=3\cdot\frac{E'V_f\cosδ}{X_s}-3\cdot\frac{V_f^2}{X_s}$

b)

$P_e=3\cdot\frac{V_fE'\sinδ}{X_s}$

c)

$P_e=3\cdot\frac{V_fE'\sinδ}{X_s}+\frac{E'V_f\cosδ}{X_s}-3\cdot\frac{V_f^2}{X_s}$

4.

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

a)

$T=3\cdot\frac{p}{ω_s}V_{eq}^2\cdot\frac{\frac{R_r}{s}}{\left(R_{eq}+\frac{R_r}{s}\right)^2+\left(X_{eq}+X_{dr}\right)^2}$

b)

$T=3\cdot\frac{p}{ω_s}V_{eq}^2\cdot\frac{R_r}{\left(R_{eq}+R_r\right)^2+\left(X_{eq}+X_{dr}\right)^2}$

c)

$T=3\cdot\frac{p}{ω_s}V_{eq}^2\cdot\frac{1}{2X_{dt}}$

5.

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

a)

$v_d^s=R_si_d^s+L_si_d^s+L_mp_d^r$

$v_q^s=R_si_q^s+L_si_q^s+L_mi_q^r$

$0=R_ri_d^r+L_rpi_d^r+L_mpi_d^s+ωL_ri_q^r+ωL_mi_q^s$ $0=R_ri_d^r+L_rpi_d^r+L_mpi_d^s-ωL_ri_q^r-ωL_mi_q^s$

b)

$V_{dS}=R_sI_{dS}+pλ_{dS}-ωλqS$ $V_{qS}=R_sI_{qS}+pλ_{qS}+ωλ_{dS}$

$V_e=R_e+pλ_e$

c)

$v_d^s=R_si_d^s+L_spi_d^s+L_mpi_d^r$ $v_q^s=R_si_q^s+L_spi_q^s+L_mpi_q^r$ $I_r=\frac{V_{eq}}{\left(R_{eq}+\frac{R_r}{s}\right)+j\left(X_{eq}+X_{dr}\right)}$

6.

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

a)

Variable with the output frequency

b)

Depending on the induction motor load

c)

Constant with the output frequency

7.

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

a)

$v_d^s=R_si_d^s+pλ_d^s-ω_0λ_q^s$ $v_q^s=R_si_q^s+pλ_q^s+ω_0λ_d^s$ $0=R_ri_q^r+pλ_q^r+\left(ω_0-ω\right)λ_d^r$

b)

$T=\sqrt[]{\frac{3}{2}}L_dI_eI_{qS}+\frac{3}{2}\left(L_d-L_q\right)I_{qS}I_{dS}$

c)

$p_T=3\cdot\frac{R_r}{s}I_r^2=3\cdot\frac{R_r}{S}\cdot\frac{V_{eq}^2}{\left(R_{eq}+\frac{R_r}{s}\right)^2+\left(X_{eq}+X_{dr}\right)^2}$

d)

$T_m=\left(λ_q^ri_d^r-λ_d^ri_q^r\right)$

8.

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

a)

$v_d^s=R_si_d^s+pλ_d^s-ω_0λ_q^s$ $v_q^s=R_si_q^s+pλ_q^s+ω_0λ_d^s$ $0=R_ri_d^r+pλ_d^r-\left(ω_0-ω\right)λ_q^r$ $0=R_ri_q^r+pλ_q^r+\left(ω_0-ω\right)λ_d^r$ $\left(λ_q^ri_d^r-λ_d^ri_q^r\right)=Jpω+T_r\left(ω,t\right)$

b)

$V_{dS}=R_sI_{dS}+pλ_{dS}-ωλ_{qS}$

$V_{qS}=R_sI_{qS}+pλ_{qS}+ωλ_{dS}$

$V_e=R_e+pλ_e$

$T=\sqrt[]{\frac{3}{2}}L_dI_eI_{qS}+\frac{3}{2}\left(L_d-L_q\right)I_qI_{dS}$

c)

$V_a\left(s\right)=R_aI_a\left(s\right)+sL_aI_a\left(s\right)+E\left(s\right)$ $E\left(s\right)=k_Vω\left(s\right)$

$T_m\left(s\right)=k_TI_a\left(s\right)$

9.

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

a)

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

b)

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

c)

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

10.

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

a)

$H_t=\frac{3}{2}\cdot\frac{N_xI_x}{2I_t}\cos\left(ωt-α\right)$

b)

$H_t=\frac{IxN_x}{2I_t}\cdot\frac{1}{2}\left(\cos\left(ωt+α\right)+\cos\left(ωt-α\right)\right)$

c)

$H_t=\frac{I_xN_x\cos\left(ωt\right)\cos\left(α\right)}{2I_t}$

11.

47 - The following equation shows the mechanical characteristic of:

$T=\frac{K_aφV}{R_a}-\frac{K_a^2φ^2ω}{R_a}$

a)

Induction motor

b)

DC motor with separated excitation

c)

DC motor with series excitation

12.

48 - What is the right electrical schematic of a four quadrants DC/DC converter?

a)

b)

c)

13.

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

a)

a) Increase of the torque ripple

b)

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

c)

c) Increase of the joule losses

14.

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

a)

a) have the same short circuit power

b)

b) have the same short circuit voltage

c)

c) have the same short circuit power factor

15.

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

a)

a) the frequency of the modulating waveform

b)

b) The amplitude of modulating waveforms

c)

c) The DC bus voltage

16.

Q 16. THE REACTIVE POWER PRODUCED BY A SYNCHRONOUS GENERATOR DEPENDS ON:

a)

a) The mechanical torque

b)

b) The rotational speed

c)

c) the excitation current

17.

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

a)

a) have the same short circuit power

b)

b) have the same short circuit voltage

c)

c) have the same short circuit power factor

18.

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

a)

a) motor with series excitation

b)

b) DC motor with separated excitation

c)

c) Induction motor

19.

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

a)

a) A DC quantity

b)

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

c)

c) A single sinusoidal waveform

20.

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

a)

a) For all load typologies

b)

b) For constant power load

c)

c) For loads with quadratic torque characteristic with speed

21.

Q. 21- THE ACTIVE POWER PRODUCED BY A SYNCHRONOUS GENERATOR DEPENDS ON:

a)

a) The mechanical torque

b)

b) The rotational speed

c)

c) the excitation current

22.

Q. 22- THE FOLLOWING EQUATIONS REPRESENT

$M_{AB}=\ -\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta\ -120°\right)$ $M_{BC}=M_{CB}\ =-\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta\ \right)$

$M_{AC}=M_{CA}\ =-\frac{1}{2}L_i\ +L_a\ \cos\left(2\theta-240°\ \right)$

a)

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

b)

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

c)

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

23.

Q. 23- THE FOLLOWING EQUATIONS REPRESENTS

a)

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

b)

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

c)

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

24.

Q. 24- WHAT IS THE TORQUE EQUATION OF A SYNCHRONOUS MACHINE IN TRANSIENT CONDITIONS?

a)

b)

c)

25.

49 - WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A THREE PHASE PWM INVERTER?

a)

b)

c)

26.

50 - WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A THREE PHASE SIX STEP INVERTER?

a)

b)

c)

27.

51 - WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A SINGLE-PHASE INVERTER?

a)

b)

c)

28.

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

a)

Voltage regulation

b)

Constant voltage/frequency regulation

c)

Frequency regulation

29.

53 - THE FOLLOWING EQUATIONS REPRESENTS

a)

The stator self inductances of an inductor motor

b)

The stator self inductance of an anisotropic synchronous machine

c)

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

30.

54 - WHAT IS THE RIGHT TORQUE EQUATION FOR THE ELECTROMAGNETIC SYSTEM SHOWN IN THE FOLLOWING FIGURE?

a)

$T=i_si_r\frac{\text{d}M}{\text{d}\theta}$

b)

$T=\frac{1}{2}i^2\frac{\text{d}L}{\text{d}\theta}$

c)

$T=\frac{1}{2}i_s^2\frac{\text{d}L_s}{\text{d}\theta}+\frac{1}{2}i_r^2\frac{\text{d}L_r}{\text{d}\theta}+i_si_r\frac{\text{d}M}{\text{d}\theta}$

31.

55 - WHAT IS THE PEAK TORQUE EQUATION OF AN INDUCTION MOTOR AT STEADY STATE CONDITION?

a)

b)

c)

32.

56 - WHAT IS THE RIGHT EQUIVALENT CIRCUIT OF AN INDUCTION MOTOR IN STEADY STATE?

a)

b)

c)

33.

57 - WHAT ARE THE RIGHT ELECTRICAL EQUATIONS OF AN INDUCTION MOTOR IN TRANSIENT CONDITIONS?

a)

b)

c)

34.

58 - WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A ONE QUADRANT STEP-DOWN DC/DC CONVERTER?

a)

b)

c)

35.

59 - WHAT ARE THE EQUATIONS FOR THE COMPUTATION OF THE EQUIVALENT CIRCUIT PARAMETERS OF THREE PHASE TRANSFORMERS?

a)

b)

c)

36.

60 - WHAT ARE THE TRANSIENT ELECTRICAL EQUATIONS OF AN INDUCTION MOTOR IN ROTATING REFERENCE FRAME?

a)

b)

c)

37.

83. WHAT IS THE MOTOR THAT IS RAPRESENT IN THIS FOLLOWING PICTURE

a)

DC Motor

b)

Synchronous motor

c)

Induction motor

38.

84. THE IMPEDENCE ZC AT THE PRIMARY WINDING IS

a)

Z * t

b)

Z / t^2

c)

Z * t^2

39.

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

a)

Increase the leakage inductances

b)

Decrease the leakage inductances

c)

Increase the rotor resistance

40.

86. RESOLVER PRODUCES:

a)

A signal proportional to the mechanical speed

b)

A signal proportional to a mechanical angle

c)

Two signals to the sine and cosine of a mechanical angle

41.

87. GIVEN THE FOLLOWING CHARACTERISTIC, IT IS

a)

Induction motor

b)

DC motor series excitation

c)

DC motor separate excitation

42.

88. GIVEN THE FOLLOWING CHARACTERISTIC, IT IS

a)

Induction motor

b)

DC motor series excitation

c)

DC motor with permanent magnet excitation

43.

89. IN AN INDUCTION MOTOR WITH ONE OPEN LOOP SPEED REGULATION, THE

CURRENT IS LIMITED USING

a)

Acceleration and deceleration ramp

b)

Slip control loop

c)

Current control loop

44.

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

a)

Reduction of the torque

b)

Increase of the stator iron losses

c)

Increase of the torque

45.

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

a)

Increase of the speed

b)

Increase of the stator iron losses

c)

Reduction of the speed

46.

92. THE FOLLOWING FIGURE REPRESENTS THE OUTPUT POWER OF

a)

Induction motor

b)

DC generator

c)

Synchronous generator

47.

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

a)

Induction motor

b)

DC motor with permanent magnet excitation

c)

DC motor with series excitation

48.

94. IN AN INDUCTION MOTOR DRIVE WITH SPEED CONTROL LOOP STATOR, THE CURRENT CONTROL WITH

a)

Slip control

b)

? (c'è scritto questo)

c)

? (c'è scritto questo)

49.

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

a)

a constant unidirectional magnetic field

b)

a rotating magnetic field

c)

a sinusoidal oscillating unidirectional magnetic field

d)

two counter rotating magnetic fields

50.

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

a)

Increase iron conductivity

b)

Realize a solid core

c)

Adding silicon in the iron alloy

51.

3 - In an induction motor is it necessary that

a)

The stator and rotor number of phases must be equal

b)

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

c)

The stator and rotor number of poles must be equal

52.

4 - The control of a sinusoidal brushless is based on

a)

A vector control using d-q axis reference frame

b)

An open loop stator current control

c)

A scalar control

53.

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

a)

The one with higher voltage

b)

The motor with higher number of poles

c)

The motor with the lower number of poles

54.

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

a)

Is variable with the output frequency

b)

Varies with the load current depending on the induction motor load

c)

Does not vary

d)

Constant with the output frequency

55.

7 - The specific iron losses represent

a)

The hysteresis losses of a ferromagnetic material

b)

The eddy current losses of a ferromagnetic material

c)

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

56.

8 - What is the right equation of the active power produce by a synchronous generator?

a)

$P_e=3\cdot\frac{V_fE'\ \sin\delta}{X_s}$

b)

$Q_e=3\cdot\frac{E'\ V_f\ \cos\delta}{X_s}-3\cdot\frac{V_f^2}{X_s}$

c)

$P_e=3\cdot\frac{V_fE'\ \sin\delta}{X_s}+3\cdot\frac{E'\ V_f\ \cos\delta}{X_s}-3\cdot\frac{V_f^2}{X_s}$

57.

9 - The following matrix represents

a)

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

b)

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

c)

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

58.

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

a)

The iron losses and the mechanical losses

b)

The rotor parameters

c)

The stator parameters

59.

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

a)

The non-linearity of stator and rotor lamination

b)

The effects of magneto-motive forces produced by stator currents

c)

The voltage drops due to stator and rotor currents

60.

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

a)

With a flux regulation

b)

With a voltage regulation

c)

With both voltage and flux regulation

61.

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

a)

Increase of the armature joule losses

b)

Reduction of the armature joule losses

c)

Increase of the excitation winding joule losses

62.

96 - A DC motor with series excitation can work:

a)

With load torque equal to zero

b)

In the first quadrant only

c)

In the first and fourth quadrant

63.

97 - What is the right drive for a cableway:

a)

Two quadrants

b)

Four quadrants

c)

One quadrant

64.

98 - What is the right drive for a train:

a)

One quadrant

b)

Four quadrants

c)

Two quadrants

65.

99 - Moving an induction motor from Europa (50Hz) to USA (60Hz) at constant voltage, there will be:

a)

A rotating flux increase

b)

Any rotating flux variation

c)

A rotating flux reduction

66.

100 - What is the magnetic configuration that reduces the iron losses:

a)

A

b)

B

c)

C

67.

101 - In an induction motor, the reduction of load torque produces:

a)

Increase of the slip

b)

Reduction of the slip

c)

Reduction of rotor speed

68.

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

a)

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

b)

The angle between the primary and secondary line voltage system

c)

The angle between the primary and secondary phase voltage system

69.

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

a)

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

b)

scalar quantities

c)

rotating space vector quantities

70.

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

a)

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

b)

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

c)

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

71.

28. - WHAT IS THE RIGHT TORQUE EQUATION FOR THE ELECTROMAGNETIC SYSTEM SHOWN IN THE FOLLOWING FIGURE?

a)

$T=\frac{1}{2}i^2\left(\frac{dL}{d\theta}\right)$

b)

$T=i_si_r\left(\frac{dM}{d\theta}\right)$

c)

$T=\frac{1}{2}i_s^2\left(\frac{dL_s}{d\theta}\right)+\frac{1}{2}i_r^2\left(\frac{dL_r}{d\theta}\right)+i_si_r\left(\frac{dM}{d\theta}\right)$

72.

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

a)

with a voltage and frequency regulation

b)

with a voltage regulation at constant frequency

c)

with a frequency regulation at constant voltage

73.

30. - THE LOCKED ROTOR TEST OF AN INDUCTION MOTOR ALLOWS TO DETERMINE

a)

The rotor parameters

b)

the magnetizing current

c)

the iron losses and the mechanical losses

74.

31. - THREE PHASES-TWO PHASES TRANSFORMATION MATRIX IN ORDER TO MAINTAIN THE POWER FORMALISM

a)

b)

c)

75.

32. - A TRANSFORMER HAS THE MAXIMUM EFFICIENCY WHEN

a)

The load impedance is equal to the short circuit impedance

b)

The Joule losses are equal to the iron losses

c)

The primary and secondary winding joule losses are equal

76.

33. - WHAT DC MOTOR CAN WORK WITH AN ALTERNATE VOLTAGE SUPPLY:

a)

DC motor with series excitation

b)

DC motor with separate excitation

c)

The permanent magnet DC motor

77.

34. - THE THEORY OF A SINUSOIDAL BRUSHLESS IS BASED ON:

a)

Scalar quantities

b)

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

c)

Rotating space vectors quantities

78.

35. - WHAT IS THE TORQUE EQUATION OF AN INDUCTION MOTOR IN STEADY STATE CONDITION?

a)

b)

c)

79.

36. - THE MAIN DRAWBACKS OF A SIX-STEP INVERTER ARE

a)

Increase of the iron losses

b)

Higher leakage currents due to dv/dt

c)

Increase of the torque ripple and increase of the joule losses

80.

61- WHAT IS THE ROTATIONAL MATRIX FROM "ALPHA-BETA" AXIS TO "DQ" AXIS?

a)

b)

c)

81.

62. WHAT ARE THE TRANSIENT ELECTRICAL EQUATIONS OF AN INDUCTION MOTOR IN FIXED REFERENCE FRAME?

a)

b)

c)

82.

63. THE OSCILLOSCOPE PICTURES SHOW THE TRACES OF TWO ELECTRICAL QUANTITIES WHEN AN INDUCTION IN NO-LOAD IS SWITCHED OFF. WHAT ARE THE TWO QUANTITIES REGISTERED BY THE OSCILLOSCOPE?

a)

Upper trace is the stator voltage, Lower trace is the rotor current

b)

Upper trace is the stator current, Lower trace is the rotor voltage

c)

Upper trace is the stator voltage, Lower trace is the rotor voltage

83.

64. WHAT ARE THE CONDITIONS FOR CORRECT PARALLEL OF TWO THREE PHASE TRANSFORMERS?

a)

-The two transformers must be of the same vector group

-The two transformers must have the same transformation ratio

-The two transformers must have the same rated power

-The two transformers should have the same short circuit voltage

b)

-The two transformers must be of the same vector group

-The two transformers must have the same secondary rated current

-The two transformers should have the same short circuit power factor

-The two transformers should have the same short circuit voltage

c)

-The two transformers must be of the same vector group

-The two transformers must have the same transformation ratio

-The two transformers should have the same short circuit power factor

-The two transformers should have short circuit voltage

84.

65. WHAT IS THE RIGHT EQUIVALENT CIRCUIT OF A THREE-PHASE TRANSFORMER?

a)

b)

c)

85.

66. WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A TWO QUADRANTS DC/DC CONVERTER?

a)

b)

c)

86.

67. IN ORDER TO REDUCE THE EDDY CURRENT LOSESS IN FERROMAGNETIC CORES, WHAT IS THE USED TECHNYOLOGY?

a)

Realize a laminated core

b)

Increase the conductivity

c)

Realize a solid core

87.

68. WHAT IS THE EQUATION OF THE INDUSTRIAL VOLTAGE DROP FOR A THREE- PHASE TRANSFORMER?

a)

𝛥𝑉 = √3 ∙ 𝑧𝑐𝑐 ∙ 𝐼

b)

𝛥𝑉𝑐𝑜𝑛𝑐 = √3 ∙ 𝐼𝑐 ∙ (𝑅𝑐𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐) + 𝑋𝑐𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐))

c)

𝛥𝑉 = 𝐼𝑐 ∙ (𝑅𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐 ) + 𝑋𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐 ))

88.

69. WHAT IS THE ROTATIONAL MATRIX FROM "DQ" AXIS TO "ALPHA-BETA" AXIS?

a)

b)

c)

89.

70. WHAT IS THE RIGHT ELECTRICAL SCHEMATIC OF A ONE QUADRANT STEP-UP DC/DC CONVERTER?

a)

b)

c)

90.

71. THE CONTROL OF A SINUSOIDAL BRUSHLESS:

a)

Field control

b)

Open-Loop control

c)

Scalar control

91.

72. THE DRAWBACK OF A TRAPEZOIDAL BRUSHLESS:

a)

High torque ripple

b)

High leakage current due to dv/dt

c)

Low dynamic performance

92.

73. TWO (DC) MOTOR HAVE THE SAME RATED POWER: WICH IS THE LARGER?

a)

The one with higher torque

b)

The one with higher speed

c)

The one with higher voltage

93.

74. WHAT IS THE EQUATION OF THE INDUSTRIAL VOLTAGE DROP FOR A SINGLE- PHASE TRANSFORMER?

a)

𝛥𝑉 = √3 ∙ 𝑧𝑐𝑐 ∙ 𝐼

b)

𝛥𝑉𝑐𝑜𝑛𝑐 = √3 ∙ 𝐼𝑐 ∙ (𝑅𝑐𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐) + 𝑋𝑐𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐))

c)

𝛥𝑉 = 𝐼𝑐 ∙ (𝑅𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐 ) + 𝑋𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐 ))

94.

75. VOLTAGE DROP ON THE SHORT CIRCUIT IMPEDANCE FOR A THREE- PHASE TRANSFORMER?

a)

𝛥𝑉 = √3 ∙ 𝑧𝑐𝑐 ∙ 𝐼

b)

𝛥𝑉𝑐𝑜𝑛𝑐 = √3 ∙ 𝐼𝑐 ∙ (𝑅𝑐𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐) + 𝑋𝑐𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐))

c)

𝛥𝑉 = 𝐼𝑐 ∙ (𝑅𝑐 ∙ 𝑐𝑜𝑠(𝜑𝑐 ) + 𝑋𝑐 ∙ 𝑠𝑒𝑛(𝜑𝑐 ))

95.

76. IN THE ELECTRICAL MACHINE WINDING WITH POLE P, THE RATIO BETWEEN THE MECHANICAL ANGLE AND ELECTRICAL ANGLE IS:

a)

θe = θm / p

b)

θe = p * θm

c)

θe = θm

96.

77. IN AN INDUCTION MOTOR CAGE, THE SKIN EFFECT ALLOWS TO:

a)

Decrease the starting current

b)

Increase the starting current

c)

Decrease the rotor resistance

97.

78. IN ORDER TO INCREASE THE WEAKING REGION IT IS NECESSARY TO USE A MOTOR WITH:

a)

Higher Peak Torque

b)

Lower Peak Torque

c)

No way

98.

79. WHAT IS THE MOTOR THAT IS RAPRESENT IN THIS FOLLOWING PICTURE:

a)

DC motor

b)

synchronous motor with anisotropic rotor

c)

induction motor

99.

THE SECTION OF THIS MACHINE IS OF:

a)

Permanent magnet synchronous motor

b)

induction motor

c)

anisotropic synchronous motor

100.

81. IN AN INDUCTION MOTOR, IN ORDER TO INCREASE THE FLUX WEAKING REGION IT IS NECESSARY TO:

a)

Increase the peak torque

b)

?

c)

?

101.

82. IN ORDER TO HAVE DIRECT TORQUE CONTROL FOR A CAGE ROTOR INDUCTION MOTOR IT IS NECESSARY TO CONTROL:

a)

The stator current in a d-q reference frame

b)

The module of the stator currents

c)

the module of the rotor currents

102.

Which is the corresponding EM

a)

DC motor with series excitation

b)

Synchronous machine

c)

Induction machine

103.

In a sinusoidal brushless, the output voltage amplitude of the converter is modified using

a)

A variable amplitude of the modulating waveform

b)

A variable DC bus

c)

Due to the permanent magnets, any regulation is requested

104.

In a trapezoidal brushless, the output voltage amplitude of the converter is modified using

a)

Due to the permanent magnets, any regulation is requested

b)

A variable DC bus

c)

A variable amplitude of the modulating waveform

105.

The area of the hysteresis cycle represents:

a)

The dissipated energy per volume unit

b)

The dissipated power in the magnetic circuit

c)

The total dissipated energy in the magnetic circuit

106.

In a permanent magnet DC motor supplied with a sinusoidal supply

a)

The produced average torque is different from zero

b)

The produced average torque is equal to zero

c)

The excitation losses increase

107.

LIFTER/WINCH has to work in:

a)

I quadrant

b)

I and II quadrants

c)

I, II, III and IV quadrants

108.

In a synchronous motor the increase of the frequency produces

a)

Increase of the rotor speed

b)

Increase of the slip

c)

Increase of the excitation current

109.

A drive for a fan works in

a)

I, II, III and IV quadrants

b)

I quadrant

c)

I and II quadrants

110.

The section of this machine is of

a)

Induction motor

b)

DC motor

c)

Synchronous motor

111.

Moving a transformer from Europe(50Hz) to USA(60Hz) the transformation ratio

a)

Decrease

b)

Doesn't change

c)

Increase

112.

In a DC motor, the increment of load torque produces, at constant voltage

a)

Speed decrease

b)

Speed increase

c)

Excitation flux increase

113.

In a synchronous motor, the reduction of the load torque produces

a)

Reduction of stator current

b)

Reduction of the slip

c)

Reduction of the rotor speed

114.

In an induction motor, the speed regulation is done with

a)

Frequency

b)

Voltage

c)

Both frequency and voltage

115.

Changing the sign of the voltage in a DC motor with permanent magnets, what happens

a)

Change T sign

b)

Doesn't change T sign

c)

Change the speed sign

116.

A DC motor with AC supply has

a)

Average torque equal to zero

b)

Average torque different from zero

c)

Something else

117.

A permanent magnet DC motor can work

a)

the constant power region only

b)

both in costant torque and constant power region

c)

in the constant torque region only

118.

The magnetic reluctance of a magnetic circuit is

a)

always negative

b)

depending on the section of the winding around it

c)

proportional to the permeability of the material

d)

inversely proportional to the permeability of the material

119.

WHAT IS THE RIGHT TORQUE EQUATION FOR THE ELECTROMAGNETIC SYSTEM SHOWN IN THE FOLLOWING FIGURE?

a)

$T=i_si_r\frac{\text{d}M}{\text{d}\theta}$

b)

$T=\frac{1}{2}i^2\frac{\text{d}L}{\text{d}\theta}$

c)

$T=\frac{1}{2}i_s^2\frac{\text{d}L_s}{\text{d}\theta}+\frac{1}{2}i_r^2\frac{\text{d}L_r}{\text{d}\theta}+i_si_r\frac{\text{d}M}{\text{d}\theta}$

120.

What is the right drive for an elevator

a)

1 quadrant

b)

2 quadrants (I and IV)

c)

2 quadrants (I and II)

121.

Moving an induction motor from Europe (50 Hz) to USA (60 Hz) the rotor speed

a)

decreases

b)

increases

c)

doesn't change

EM 1-121

Total questions: 121

Worksheet time: 10hrs 5mins

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