MMET 301 exam 1 questions and
answers graded A+
Electric Motor - correct answer ✔✔Current carrying conductor produces an electric field that may be
attracted or repelled by another magnetic field
Transforms electric power into rotary motion
Unit system for north America - correct answer ✔✔NEMA - national electrical manufacturers
association)
Unit system for not north America - correct answer ✔✔SI - international standard (also known as IEC)
Standards - correct answer ✔✔CEEMA- Canadian electrical & electronics manufacturers alliance
Typical frequency - correct answer ✔✔60 Hz
Frame sizes (example - 145TC) - correct answer ✔✔Two digits
Shaft center height in 16ths of an inch
Three digits
First two digits indicate height in 4ths of an inch
Third digit refers to mounting holes on motor base
Letters
Know chart on page 228?
Motor heating - correct answer ✔✔Raw polarity
Causes of overheating: high/low voltage, slow or repeated starts, etc
Loads - correct answer ✔✔Constant torque
, Variable torque
Constant torque - correct answer ✔✔Increase in demand for horsepower proportional to speed increase
Variable torque - correct answer ✔✔Increase in demand for horsepower is greater than the increase in
speed
Motor insulation - correct answer ✔✔Windings are coated with insulation to prevent shorting to
adjacent conductors or the motor frame
Temperature limits indicated by letter designation
Chart on page 228
Service factor - correct answer ✔✔"SF" - Amount of overload a motor can deliver without overheating
Speed torque curves - correct answer ✔✔Maximum available torque a motor can deliver at any given
speed
Enclosures - correct answer ✔✔Guarded to prevent personnel from touching a moving or electrically live
part
DP enclosures - correct answer ✔✔"Drip-proof" enclosures
Referred to as ODP motor
Clean, dry, indoor industrial environment
Vents keep particles falling 15 degrees or less from entering
Weather-protected machines - correct answer ✔✔"WP I" - enhanced version of DP
Vents minimize particles from entering
"WP II" - vents intake and discharge particles with abrupt changes to minimize debris in electric parts
DPBV enclosures - correct answer ✔✔Drip-proof, blower ventilated
answers graded A+
Electric Motor - correct answer ✔✔Current carrying conductor produces an electric field that may be
attracted or repelled by another magnetic field
Transforms electric power into rotary motion
Unit system for north America - correct answer ✔✔NEMA - national electrical manufacturers
association)
Unit system for not north America - correct answer ✔✔SI - international standard (also known as IEC)
Standards - correct answer ✔✔CEEMA- Canadian electrical & electronics manufacturers alliance
Typical frequency - correct answer ✔✔60 Hz
Frame sizes (example - 145TC) - correct answer ✔✔Two digits
Shaft center height in 16ths of an inch
Three digits
First two digits indicate height in 4ths of an inch
Third digit refers to mounting holes on motor base
Letters
Know chart on page 228?
Motor heating - correct answer ✔✔Raw polarity
Causes of overheating: high/low voltage, slow or repeated starts, etc
Loads - correct answer ✔✔Constant torque
, Variable torque
Constant torque - correct answer ✔✔Increase in demand for horsepower proportional to speed increase
Variable torque - correct answer ✔✔Increase in demand for horsepower is greater than the increase in
speed
Motor insulation - correct answer ✔✔Windings are coated with insulation to prevent shorting to
adjacent conductors or the motor frame
Temperature limits indicated by letter designation
Chart on page 228
Service factor - correct answer ✔✔"SF" - Amount of overload a motor can deliver without overheating
Speed torque curves - correct answer ✔✔Maximum available torque a motor can deliver at any given
speed
Enclosures - correct answer ✔✔Guarded to prevent personnel from touching a moving or electrically live
part
DP enclosures - correct answer ✔✔"Drip-proof" enclosures
Referred to as ODP motor
Clean, dry, indoor industrial environment
Vents keep particles falling 15 degrees or less from entering
Weather-protected machines - correct answer ✔✔"WP I" - enhanced version of DP
Vents minimize particles from entering
"WP II" - vents intake and discharge particles with abrupt changes to minimize debris in electric parts
DPBV enclosures - correct answer ✔✔Drip-proof, blower ventilated
