WorksheetsThree-Phase Motor Principles
Total questions: 35
Worksheet time: 18mins
What do three-phase motors convert three-phase AC into?
Electrical energy
Mechanical energy
Chemical energy
Thermal energy
Which type of motors are extremely rugged and require minimal maintenance?
Single-phase motors
Three-phase motors
DC motors
Synchronous motors
One of the three basic types of three-phase motors is the ________ induction motor.
Squirrel-cage
Shaded-pole
Universal
Stepper
One of the three basic types of three-phase motors is the ________ induction motor.
Wound-rotor
Synchronous
Universal
Stepper
One of the three basic types of three-phase motors is the ________ motor.
Synchronous
Stepper
Universal
Shaded-pole
What is the principle of operation for all three-phase motors?
The rotating magnetic field.
Direct current excitation.
Permanent magnet interaction.
Electrostatic induction.
The magnetic field rotation in three-phase motors is caused by which of the following?
Voltages are 120° out of phase
Voltages periodically change polarity
The arrangement of the stator windings
All of the above
Voltages in a three-phase motor are ______ out of phase.
120°
90°
60°
180°
Voltages in three-phase motors periodically change polarity.
True
False
What is the rotational movement of the motor shaft referred to as?
Torque
Voltage
Current
Resistance
What is the Prony brake used to measure?
Speed
Torque
Temperature
Voltage
The formula to calculate torque is T = ___ × ___.
F × r
m × a
P × V
W × t
T is the torque in _________.
newton-meters (Nm)
joules (J)
watts (W)
kilograms (kg)
F is the force in _________.
newtons (N)
joules (J)
watts (W)
meters (m)
R is the radius in _________.
meters (m)
seconds (s)
kilograms (kg)
amperes (A)
A dynamometer indicates 20N at a radius of 150mm (from the center of the shaft). What is the torque imposed?
1.5 Nm
3.0 Nm
2.0 Nm
0.3 Nm
What is the formula for calculating mechanical power (P) in a rotating machine?
P = (T × n) / 9.55
P = (T + n) × 9.55
P = T / (n × 9.55)
P = (T × n) × 9.55
In the formula P = (T × n) / 9.55, what does 'P' represent?
Mechanical power in watts (W)
Torque in newton-meters (Nm)
Rotational speed in revolutions per minute (rpm)
Electrical resistance in ohms (Ω)
In the formula P = (T × n) / 9.55, what does 'N' represent?
Rotational speed (rotational frequency) in revolutions per minute (r/min)
Torque in Newton-meters (Nm)
Power in kilowatts (kW)
Time in seconds (s)
In the formula P = (T × n) / 9.55, what does 'T' represent?
Torque in Nm
Time in seconds
Temperature in Kelvin
Tension in Newtons
In the formula P = (T × n) / 9.55, what is the value of the constant?
9.55
8.25
10.00
7.50
What is the formula for calculating horsepower (Hp) for electric motors rated in horsepower?
Hp = (T × n) / 7121
Hp = (T × n) / 9549
Hp = (T × n) / 5252
Hp = (T × n) / 746
What does 'Hp' represent in the formula Hp = (T × n) / 7121?
horsepower
heat power
hydraulic pressure
high potential
What does 'n' represent in the formula Hp = (T × n) / 7121?
rotational speed (rotational frequency) in revolutions per minute (r/min)
torque in Newton-meters (Nm)
power output in horsepower (Hp)
time in seconds (s)
What does 'T' represent in the formula Hp = (T × n) / 7121?
torque in Nm
temperature in Celsius
time in seconds
thrust in Newtons
In conversions, 1 horsepower (hp) is equal to how many watts (W)?
746 W
1000 W
550 W
860 W
The output true power of a motor delivering 80Nm at a speed of 1760 r/min is? (Provide your answer in Watts)
14,734.4 Watts.
10,500 Watts.
8,900 Watts.
17,600 Watts.
Calculate the output horsepower of a motor delivering 33Nm at a speed of 1150 rpm.
The output horsepower is approximately 5.09 hp.
The output horsepower is approximately 2.45 hp.
The output horsepower is approximately 8.12 hp.
The output horsepower is approximately 12.67 hp.
Calculate the torque output using the formula: T = (P × 9.55) / N, where P = 7500 W and N = 1740 r/min. What is the torque output?
41.164 Nm
32.500 Nm
55.200 Nm
25.000 Nm
The motor is operating at half load. Calculate the torque output at half load using the value from the previous calculation. The torque output at half load is ______ Nm.
20.582 Nm
10.291 Nm
15.000 Nm
25.000 Nm
What is the torque output (in Nm) of a 10 hp motor running at 1740 r/min at full load?
40.93 Nm
25.67 Nm
55.12 Nm
10.25 Nm
What is the torque output (in Nm) at half load 30N at 1m?
20.47 Nm
10.24 Nm
30.71 Nm
15.00 Nm
What is the formula for calculating efficiency in an electric motor using output and input power? Efficiency = ______ / P_IN(ELECT)
P_OUT(MECH)
P_IN(MECH)
P_OUT(ELECT)
P_LOSS
Efficiency is the ratio of ______ to the electrical power input for any given load level in an electric motor.
mechanical power output
electrical resistance
thermal energy loss
rotational speed
Which of the following is a correct formula for calculating efficiency?
Efficiency = P_OUT(MECH) / P_IN(ELECT)
Efficiency = P_IN(ELECT) / P_OUT(MECH)
Efficiency = P_OUT(MECH) + P_LOSSES(HEAT) / P_IN(ELECT)
Efficiency = P_OUT(MECH) / (P_OUT(MECH) + P_LOSSES(HEAT))
