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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

Good candidates for VFDs are...

pieces of equipment with variable but consistent loads that will benefit from custom speed control