1What is a motor slator?
The housing of the motor that contains the windings
2What is the rotating part of an AC motor called?
Rotor
3What is the rotating part of a DC motor called?
Armature
4What is a split phase motor?
Single phase AC motor with a start and run winding
5How does the resistance of a start winding help to start a motor?
The higher resistance causes a phase shift between the voltage and the current
6Describe the torque capabilities of a split phase motor.
Low starting torque, medium running torque
7Give some examples of applications where split phase motors are used.
Fans, medium sized blowers
8Can a split phase motor be used for an air compressor? Why?
No, not enough starting torque
9How does a capacitor start motor vary in design from a split phase motor?
Has a start capacitor wired in series with the start winding.
10Where is the capacitor connected in a capacitor start motor?
In series with the start winding
11Describe the torque characteristics of a capacitor start motor.
High starting torque, and medium running torque
12Give some applications for capacitor start motors?
Large blowers, compressors, large choppers and mixers
13What does the capacitor on a capacitor start motor do to the electric current on the motor to increase its starting torque?
Causes additional phase shift
14What is the function of a centrifugal switch on a split phase or capacitor start motor?
To remove the start winding and start capacitor from the circuit when the motor gets to about 2/3 of its fill speed
15How does a centrifugal switch work?
Centrifugal force from the motor spinning opens the contacts
16How much is the starting current of a split phase or capacitor start motor?
5 to 6 times the normal running current
17How long does the centrifugal switch remain closed when the motor is started?
Until the motor gets to about 2/3 full speed
18If the centrifugal switch has two sets of contacts, what is the purpose of the second set?
A safety circuit to remove some other component in the machine if the motor is not running
19If dirt or dust keeps the centrifugal switch contacts from making a good connection, how will the motor act?
It will hum and draw high amperage, but will not start
20What is PSC motor?
Permanent Split Capacitor
21PSC motors are normally used for what applications?
Fan motors, household air conditioner compressors
22Describe the torque characteristics of a PSC motor.
Low starting, medium running torque
23How does a PSC motor differ from a capacitor start motor?
Low starting torque, and uses only a run capacitor
24Does a PSC motor used a centrifugal switch?
No
25What applications would need a capacitor start, capacitor run motor?
High torque, larger horsepower
26How dies a start capacitor differ from a run capacitor?
High microfarad, and housed in a plastic housing instead of a metal housing
27What will happen if a start capacitor remains in the circuit too long?
It will self destruct
28What will happen if a run capacitor remains in the circuit too long?
Nothing, it is designed to be in the circuit all the time
29Describe the torque characteristics of a shaded pole motor.
Low start and low running torque
30Give some common applications for shaded pole motors.
Small fans
31Does a shaded pole motor use a centrifugal switch?
No
32Does a shaded pole motor have a start winding?
No
33When can sleeve bearings be used on motors?
Low radial loads
34What is the major disadvantage of sleeve bearings?
Have to be oiled all the time
35What type of lubricant should be used on sleeve bearings for a normal motor application?
20 weight motor oil
36When should ball bearing motors be used?
High radial loads, like belt drive applications
37What applications require the use of sealed ball bearings?
Pumps, disposers, etc. where water or grease may get into the motor
38Describe an open drip proof motor.
Has holes in the ends of the motor housing for cooling are to pass through
39Describe a (TEFC) totally enclosed fan cooled motor.
Totally enclosed, circulated air over the outside of the motor
40When is a TEFC motor needed?
Dirty, or contaminated enviornments
41Most electric motor burn outs are caused by what?
Overheating
42What preventive motor maintenance is required for ODP motors to prevent burn out?
Clean out the air holes and blow out the motor
43What preventive maintenance is required for a TEFC motor to prevent chances of burnout?
Clean the outside if the motor housing
44What does the motor horsepower rating indicate?
The amount of work the motor can do
45What is the max. variation from motor nameplate voltage that can be tolerated without possible problems?
+ or - 10%
46What does a motor full load amp rating refer to?
The max. amperage when a motor is fully loaded
47Do most motors operate at less that full load amperage?
Yes
48If a fan has an adjustable pulley on it, what will happen to the motor as the pulley is adjusted to make the fan run faster?
It could overload the motor
49Give four possible reasons for a motor to draw excessive amperage?
Overloaded, low voltage, high voltage, binding load, bad bearings
50What does the service factor rating on a motor mean?
A safety factor, excessive amperage than the motor can supposedly handle
51What characteristic of a motor does frequency affect?
RPM
52A standard general purpose motor will have what insulation class rating?
A
53A heavy duty motor will usually have an insulation class rating of what?
B
54Class F or H insulated motor are used in what applications?
High temp. applications like fryer filter pump
55What does the temp. rise rating of a motor refer to?
How much higher temp. the motor will normally operate over the ambient temperature.
56What does an ambient temp. rating of a motor refer to?
The max. ambient temp. the motor can operate in
57Why is the frame number of a motor so important?
Tells you all the info. about the physical sized characteristics of the motor
58Give the five minimum facrs that you will need to get a replacement motor?
Voltage, RPM, phase, frame number, and type of motor
59Describe the torque characteristics of a three phase motor?
Highest starting and running torque
60Does a three phase motor have a start winding?
No
61Which amp rating on a contactor must be used when sizing for a motor application?
Inductive or FLA
62What is the purpose of an automatic reset thermal protector?
To shut down the motor if it overheats
63When should a manual reset thermal protector be used?
When unexpected starting of the motor could be dangerous
64What does a motor thermal protector actually sense?
Temp. of the motor windings
65What type of fuses must be used for motor applications?
Time delay
66What is the problem with just using a normal branch line circuit breaker to protect a motor?
Amperage rating is not close enough to the motor FLA rating
67In what range of amp ratings are motor overload heaters available?
Fractions of an amp
68What is the advantage of using a motor starter over other forms of motor protection?
Can protect a motor against overloading much better
69What is the major advantage of DC motors in applications in the Foodservice industry?
Variable speed
70What is a commutator and what is its purpose?
Switching contacts on the armature, to constantly reverse polarity to the armature windings
71What is the function of motor brushes?
Conduct the - or + line to the commutator segments
72When should you replace motor brushes?
When they are worn about 1/2 way down
73What will happen if motor brushes are allowed to wear excessively?
They will damage the commutator
74What is a permanent magnet DC motor?
A motor with a permanent magnetic field
75Why is a permanent magnet DC motor better for speed control than a wire wound field motor?
Maintains better torque over a wider speed variation
76Why will good DC motor preventive maintenance include cleaning the inside of the motor housing?
To get all the carbon dust out from the brushes, that can cause the motor to short out
77What applications are universal motors used for?
Mixers, and some power tools
78If a motor hums and will not start, but spins freely by hand, how would you troubleshoot the problem?
Check the start capacitor if it has one. Blow out the motor and try to start it again, it may start if dirt on the centrifugal swtich was the problem, if not replace the motor
79How do you check a motor capacitor?
Either with a digital or analog meter
80If the needle on your ohm meter moves across the scale to zero and stays there when checking a capacitor, what is wrong with the capacitor?
Shorted
81How would you troubleshoot a motor that runs but draws excessive amperage?
Check the voltage to the motor, check the motor shaft and load and make sure it is not tight or binding. Check the run capacitor if it has one
82Is it ever acceptable for a motor to draw more than full load amperage?
No, only on start up
83How can you tell when motor bearings are failing?
Noise, or tightness when the motor shaft is turned
84What normally causes motors to vibrate?
Loads that are out of balance
85What must be done with a blower wheel that keeps coming off of a motor?
Replace it. Check the shaft of the motor to make sure it was not damaged also, if it is, the motor will have to be replaced also.
86How can you tell if motor overloads are kicking out from a motor problem or weak overloads?
Check the amp draw. If amperage is high, there is a motor or load problem. If amperage is OK, there is an issue with the overload
87How can you tell what the amperage rating is of a overload heaters?
Get the number off of it and call the control distributor to find the amp rating of the overload heater
88Describea brushless DC motor.
A permanent magnet DC motor, where the magnet in on the armature. A motor control constant changes the polarity to the field windings
89What switches the polarity to the field on a brushless DC motor?
Motor controller
90What is an ECM motor and how does it work?
Brushless DC motor with the controller mounted to the motor housing
91Why are ECM motors becoming so popular?
Energy efficiency and variable speed applications
92Brushless DC and ECM motor windings are wound to use 3 phase power. (T or F)
True
93What kind of power is fed to an ECM motor AC or DC?
AC
94What is the major downfalls to using ECM motors?
Cost and lack of local availability
95Most replacement ECM motors will have to be purchased where?
From the equipment OEM