Chapter 11 - Motors Flashcards
Electric motors operate on the principle that a force acts on a conductor when it carries current in a magnetic field
True
AC motors typically direct on AC power lines.
True
D-flange motors have clearance holes without threads and can be directly bolted on to machinery.
True
AC motors contain two main parts-the stator and the rotor.
True
AC motor stators contain windings with two or more magnetic poles per phase.
True
AC induction motor rotors consist of a laminated cylinder with plastic bars in slots around the outer part of the cylinder.
False
The rotational speed of the stator’s magnetic field is called the synchronous speed of the motor.
True
Locked-rotor torque available at zero speed for accelerating the load.
True
Polyphase motors are available in ratings from fractional to thousands of horsepower.
True
The Canadian equivalent of NEMA is NAFTA.
False
The majority of general-purpose, three-phase motors manufactured after October 24, 1997 are required to meet EPACT.
True
Inverters or Variable Frequency Drives (VFD) were developed to control the voltage and frequency to DC motors.
False
DC motors are less complex and costly than corresponding AC induction motors.
False
There are two basic types of DC motors - brush and brushless.
True
Three types of wound-field DC motors included series, shunt, and compound wound.
True
Motors that are recognized as meeting North American standards for hazardous locations also can be assured to meet IEC standards.
False
Another name for a 3-phase motor is
Polyphase motor
Motors that operate on 60 Hz power systems are used in
Mexico
Doubling motor load:
Raises motor heating four times.
Variable-torque loads include
Fans
The synchronous speed of a 4 pole, 60 Hz motor is
1800
The difference between synchronous and actual rotor speed for a Design B motor is
3-5 percent at full load
PM motors are offered in sizes from
1/4 to 5 HP
General-purpose brushless DC motors are widely available with ratings up to about
20 HP at 1800 rpm
A typical DC motor option is a
Tachometer, Blower, Space heater (All of the above)
The majority of general-purpose, three phase motors manufactured after ____ are required to meet EPACT mandates.
1997
Locked-rotor torque is torque available at what speed for accelerating the load?
0
AC motor stators contain windings with two or more poles per phase. What type of poles are these?
Magnetic
What type of motor consists of two basic types including brush and brushless?
DC
Brushless motors do not have what?
Both Brushes and Commutators
