Name the three requirements for induction to take place.
A conductor, a magnetic field, and relative motion between them
100
A motor’s nameplate voltage rating is the __________ voltage that should be connected for best operating performance.
Optimal
100
How do you reverse the direction of rotation of a 3-phase motor?
Interchange (swap) any two of the three power leads
100
Which NEMA design is the most common general-purpose motor used for fans, blowers, and pumps?
Design B
100
A 3-pole rheostat is used to switch a set of __________ in or out of a wound-rotor circuit (high-wattage resistors for speed control).
Resistors
200
What is the ability of a material to conduct magnetic flux called?
Permeability
200
What does the locked-rotor indicating code letter on a motor nameplate represent?
The range of locked-rotor current draw per horsepower (LRA range)
200
What is the synchronous speed of a 60 Hz, 2-pole motor?
3,600 rpm
200
What part of a squirrel-cage rotor provides a short-circuit path for current to circulate in the rotor?
Shorting ring *
200
Brushes may damage the slip rings if they do not have good softness and __________.
Conductivity
300
Which left-hand rule explains the direction of a magnetic field around a coil relative to the direction of current in the coil?
Left-Hand Coil *
300
What nameplate rating indicates how much overwork (load beyond rated) a motor can handle without damage?
Service factor
300
What is the fixed, unmoving part of a motor (core and windings) that converts electrical energy into the energy of a magnetic field?
Stator
300
Which NEMA design motors are suitable for equipment with very high-inertia starts, such as cranes and hoists?
Design D
300
Look at the power-factor waveform. Is this lagging, leading, or unity power factor? [Figure: qr2 pf lagging]
Lagging
400
Which rule is used to determine the direction of torque (rotation) in a motor?
Right-Hand Motor Rule
400
What abbreviation on a nameplate means the motor is intended to operate for unlimited time periods (continuous duty)?
CONT
400
Using the sinewave graph, match the angle where each phase is at a positive maximum. (Phase A / Phase B / Phase C) [Figure: qr2 sinewave phases]
Phase A = 240°; Phase B = 0°; Phase C = 120°
400
Match each letter on the induction motor illustration to its part. [Figure: qr2 induction parts]
A = laminations/rotor; B = shorting ring; C = conductor bars/squirrel cage; D = fan blade; E = shaft
400
The rotor winding coils of a wound-rotor motor are made up of __________.
Insulated copper conductors (wire)
500
Every time AC current passes which point of the sine wave do the direction of current flow and the polarity of the magnetic field change?
Zero (zero crossing)
500
What does the frame size number on a motor nameplate designate?
Standard dimensions of the motor housing, shaft, and mounting holes
500
Identify the labeled points on this motor torque curve: locked-rotor torque (LRT), pull-up torque (PUT), breakdown torque (BDT), and full-load torque (FLT). [Figure: qr2 torque curve]
LRT = A; PUT = B; BDT = C; FLT = D
500
A wound-rotor motor delivers higher __________ than a squirrel-cage induction motor without overloading the electrical system.
Starting torque
500
This illustration shows a synchronous-motor starting circuit. Which component discharges AC potential that builds up in the rotor field windings during start? [Figure: qr2 sync start circuit]