Flashcards in Motors Deck (28)
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1
Rotor
The moving part to which the spinning shaft is attached
2
Stator
The stationary part either inside or around the rotor
3
Magnetic Field
Created with either permanent magnets or electromagnets
4
Windings
Coils of wire through which the current flows to produce an opposing magnetic field
5
If the windings are on the rotor, the stationary input wires lead to _______ that are held against the spinning ______ which distributes it to the windings.
brushes, commutator
6
Electronically Commutate Motor (ECM)
A small hp brushless (the magnetic field rotates around stationary windings) DC motor that is usually higher efficiency than an AC motor of the same size. Commonly found in HVAC fans.
7
Induction Motor
Most common AC motor.
Has stationary windings around a rotor containing permanent magnets. They're sealed, self-starting, reliable, rugged, and low cost. No brushes.
8
Single Phase AC induction motor
Extensively used for smaller loads such as appliance fans. Not practical above 5-10 hp
9
3-phase AC induction squirrel cage motors
The most widely used industrial motors in the world
10
Nameplate Horsepower (NPHP) of 15-hop means
the motor produces 15 hp of work at full load.
11
1 HP =
746 Watts
12
Motor efficiency
Measures the effectiveness by which electrical energy is converted to mechanical energy.
13
Load factor =
Actual load HP / nameplate HP
14
Ways to measure actual load factor:
-Measure speed of motor in RPM with tachometer and compare to nameplate
-Use volts, amps, and power factor
15
Actual Electrical Load =
NPHP x Load Factor
16
The speed of a synchronous motor is determined by
the number of magnetic poles within the motor and the frequency of the electricity
17
Motor synchronous speed (RPM) =
(120 x frequency) / # of magnetic poles
18
Asynchronous motor
Always have a difference between its loaded RPM (lower) and its synchronous RPM (higher). This is called slip.
19
Duty Cycle Rating
Indicates its operational profile in terms of starting and stopping, speed variation, and temp. Not used for energy calculations.
20
Duty is used to...
match the correct motor to the correct application, otherwise overheating and premature failure can occur.
21
Duty S1
Continuous duty - runs long enough to reach steady state temperature. Most common motor (compressors)
22
Duty S2
Short term duty - brief operation followed by long rest (appliances)
23
Duty S3
Intermittent periodic duty - consistent on and off (drill press)
24
Variable Frequency Drives (VFD)
Motor controls that vary the speed of a motor to better match the load being put on the motor
25
VFDs reduce the speed of the motor by adjusting...
the frequency of the electrical input
26
A reduction in speed of a fan or pump motor results in...
a large reduction of horsepower
27
VFDs can save between _________ % of the energy used by a typical motor
20-30%
28
