Mechanics (Motors Quiz) Flashcards
What are the 2 basic types of motors?
AC and DC
What are the 2 basic types of AC motors?
Single Phase (Single Ø)
3 Phase (3 Ø)
What are the common AC voltages for Single Phase?
110VAC, 115VAC, 120VAC, 220VAC, 230VAC, and 240VAC
What are the common AC voltages for 3 Phase?
208VAC, 220VAC, 230VAC, 240VAC, and 480VAC
What increment (of an inch) are frames measured in (base to shaft center) if the tag has 2 numbers?
1/16”
What increment (of an inch) are frames measured in (base to shaft center) if the tag has 3 numbers?
1/4”
On a 3 number tag, what does the 3rd number refer to?
Bolt pattern
What are the shaft and mounting types listed on the motor’s tag?
T, TC, TS, C, JM, and JP
T - Long Shaft
TC - C Face with Long Shaft
TS - Short Shaft
C - C Face
JM - Closed Coupled Pump
JP - Closed Coupled Pump
What are the common reasons AC motors overheat?
•High/Lower Voltage
•Frequent/Repeated Starts
•High Ambient Temperature
•Clogged/Dirty Vent holes/cooling fins
•Voltage imbalance in 3 phase motors
What is the same as the motors insulation rating?
Motor class
How are motors classed?
Letter (A,B,F,H) indicating how much temperature increase the windings can withstand
What is the Service Factor? (SF)
Amount of load the motor can deliver without overheating.
What are the 3 common Service Factors?
SF 1.0 - Rated Load on nameplate
SF 1.15 - 115% Rated load
SF 1.25 - 125% Rated load
When speed is low, torque is ____
High
When speed is high, torque is ___
Low
What is a C Face mount?
Motor supports driven unit (pump)
What is a D Flange mount?
Motor is supported by driven unit (pump)
What are the types of overload protection on single phase motors?
ATO, MTO
What are the types of overload protection for 3 phase motors?
Thermostats, thermistors, and resistance temperature detectors
What are the basic parts of AC motors?
Two main parts:
•Stator
•Rotor
Others:
•End Bracket
•Fan End Bracket
•Fan
•Fan Shroud
•Lifting Lug
What are motor poles?
Number of windings
The more poles in a motor, the ____ the RPM is and torque is proportionally ____
Lower, Higher
What is slip?
Difference between synchronous speed and actual speed. (Between 1% and 5%)
Which is more common, single phase or 3 phase? Why?
3 phase. Cheaper and more efficient. Considered the workhorse of industry (not ours)
What is the primary problem with single phase motors?
Little to no start up torque.
What are the methods of starting single phase motors?
Shaded Pole, Split Phase, Capacitor Start, and Perm Split Capacitor
Describe Shaded Pole
Copper loop, called shading ring, surrounds part of the stator pole
Describe Split Phase
Start windings positioned 90° from run windings
Describe Capacitor Start
Has a capacitor in series with start winding. (Most commonly used in industry, more than double starting torque)
