Electric Motor
service factor
indicates the maximum load that can be successfully carried by the motor if it is to operate continuously and remain within a safe temperature range
In the ___(ac or dc?) motor, current is sent into the STATOR winding which is placed in a stationary laminated iron core; the rotating element may or may not be a set of magnet poles.
AC motor
In the ___(ac or dc?) motor, current is sent into the ARMATURE winding, which is placed in-between a set of radially supported magnet poles.
DC motor
Synchronous
A type of AC motor capable of raising the power factor of systems having large induction motor loads.
thermal protector
device which protects the motor against overheating due to overload or failure to start
single-phase
has one voltage applied to the motor in the shape of a sine wave
three-phase
has three individual voltages applied to the motor. NOTE The three-phase are at 120 degrees with respect to each other so that peaks of voltage occur at even time intervals to balance the power received and delivered by the motor throughout its 360 degrees of rotation.
locked-rotor current
maximum current required to start the motor
breakdown torque/ pull out torque
maximum torque a motor can develop during overload without stalling
duty rating
refers to how frequently the motor is started and how long it will run each time it is started
rotor/ armature winding
rotating part of electric motor which is typically constructed of a laminated steel core containing current-carrying copper wires
frame designation
standardized motor mounting and shaft dimensions as established by National Electric Manufacturers Association (NEMA) or International Electrotechnical Commission (IEC)
stator/ field poles
stationary part of electric motor consisting of copper windings which is placed in a laminated iron core
temperature rise
temperature of a motor operating under rated conditions, which is above ambient temperature
torque
twisting or turning force produced by the motor
What motor has up to 3.73 kW rating which is commonly designed to operate on either direct current or alternating current?
universal motor
"Branch-circuit conductors that supply a single motor used in a continuous duty application shall have an ampacity of not less than ___ percent of the motor's full-load current rating."
125 %
Motor efficiencies and power factors shall meet or exceed the following values to conform with Philippine Electrical System at +10% 230 volts and ____ Hz frequency.
60 Hz
Wound-rotor
A type of AC motor, wherein secondary windings are wound with discrete conductors with the same number of poles as the primary winding on the stator
shunt-wound motor
A type of DC motor, in which the field winding is connected in parallel with the armature. NOTE: The shunt motor is used in constant speed application.
Series-wound motor
A type of DC motor, in which the field winding is connected in series with the armature. NOTE The series motor is used in applications where a high starting torque is required.
Compound-wound motor
A type of DC motor, which has a series-field and shunt-field winding. NOTE In compound motor, the drop of the speed-torque characteristics may be adjusted to suit the load.
Integral-horsepower
A type of motor built in larger frames having a continuous rating equal to and greater than 1 hp, open type, at 1700 rpm to 1800 rpm.
Fractional-horsepower
A type of motor built in smaller frames having a continuous rating of less than 1 hp, open type, at 1700 rpm to 1800 rpm.
Squirrel-cage
A type of AC motor wherein the rotor or secondary winding consists merely of 28 identical copper or cast-aluminum bars solidly connected to conducting end wings on each end, thus forming a "squirrel-cage" structure. The starting kVA of a squirrel-cage motor is indicated by a code letter stamped on the nameplate. Table 4 shows the corresponding kVA for each code letter.
starting torque/ locked rotor torque
motor torque at zero speed or the maximum torque required to start the load
phase
number of individual voltages applied to the motor
