Gears Study Guide
8.AC induction motor rotors consist of a laminated cylinder with plastic bars in slots around the outer part of the cylinder. a. True b. False
F
Bronzes account for most ferrous gears
F
Enclosed gear speeds are generally limited to 1,200 rpm
F
Speed Reducers can be: a.Base-mounted b.Shaft-mounted c.A and b above. d. None of the above
c.A and b above.
16.Permanent split-capacitor motors offer high efficiency and power factors as well as high starting and breakdown torques. a. True b. False
?
28.A step motor is a spring-mass system that oscillates when pulsed at its natural frequency. a. True b. False
?
30.Most stepping motors have four sets of windings per pole, a so-called Quadra filer arrangement. a. True b. False
?
In spur gear terminology the play between mating teeth is called a.Backlash b.Clearance c.Tooth relief d.Working space
A. Backlash
When ordering gears, the following should be specified: [Select of that apply.] a. Diametral pitch b. Tooth size c. Pitch diameter d. Gear size
ALL of the above
In spur gear terminology the height of a tooth above a pitch circle is called: a.Dedendum b.Addendum c.Diametral pitch d.Circular pitch
B. Addendum
Nonferrous gear materials include: a.Ductile iron b.Sintered powder metal c.Bronze (copper alloy) d.Carbon steel
C. Bronze (copper alloy)
Ferrous gear materials include: a.Copper b.Aluminum c.Cast iron d.Zinc
C. Cast Iron
13.The Canadian equivalent of NEMA is NAFTA. a. True b. False
F
15.Inverters were developed to control the voltage and frequency to DC motors. a. True b. False
F
17.DC motors are less complex and costly than corresponding AC induction motors. a. True b. False
F
20.In DC motors, as the power ratings increase, the armature voltage ratings decrease. a. True b. False
F
21.Brushless motors have magnets mounted on the stator. a. True b. False
F
25.Step motors are used for their high speed and high torque. a. True b. False
F
26.Hybrid step motors are popular for low torque applications. a. True b. False
F
3. The output of general purpose motors in the U.S. is rated in horsepower and cost. a. True b. False
F
Face gears are used mostly to transmit motion and heavy loads.
F
Gears are still quite useful even after 1 or 2 teeth have broken.
F
Gears can only be lubricated using oil.
F
Helical gears tend to have low efficiencies into the 60 percent to 70 percent range.
F
Hypoid gears are stronger than spiral gears but are much noisier due to their high contact ratio.
F
The most commonly used gear plastics are polypropylene, polyamid, and phenolic.
F
The shape of spur gear teeth is based on an involute form which produces a sliding contact rather than a rolling contact between mating teeth.
F
The simplest and most common bevel gear is the spiral.
F
Gears supplied as assembled are referred to as open gearing.
False
23.Servomotors are widely used for rapid-reversing and precision-positioning applications. a. True b. False
T
24.Servomotors are typically supplied in TENV enclosures. a. True b. False
T
27.Step motors exhibit different speed-torque characteristics than other types of motors. a. True b. False
T
29.Motors that are recognized as meeting North American standards for hazardous locations also can be assured to meet IEC standards. a. True b. False
T
4.Design C motors using double squirrel cage rotor construction are best suited for inverter applications. a. True b. False
T
5.D-flange motors have clearance holes without threads and can be directly bolted on to machinery. a. True b. False
T
6.AC motors contain two main parts - the stator and the rotor. a. True b. False
T
7.AC motor stators contain windings with two or more magnetic poles per phase. a. True b. False
T
9.The rotational speed of the stator's magnetic field is called the synchronous speed of the motor. a. True b. False
T
A breather is a plug with a hole that permits air flow inside a gearbox.
T
AC motors typically operate directly on AC power lines. a. True b. False
T
Cycloidal gearing is unique in that all torque transmitting parts roll rather than grind.
T
Double helical gear sets use two pair of opposed gear teeth to eliminate thrust load.
T
Electric motors operate on the principle that a force acts on a conductor when it carries current in a magnetic field. a. True b. False
T
Gears used to transmit power through right angles on nonintersecting shafts are called worm gears.
T
Hypoid gear shaft axes do not intersect.
T
Inadequate lubrication of gears will cause undo wear.
T
Plastic gears work well in corrosive environments.
T
Skew tooth gears are like spiral gears except the teeth are not curved.
T
The efficiency of worm gears tends to be lower than other gear types.
T
The side of a spur gear tooth is called a tooth surface.
T
The teeth of herringbone gears join in the middle.
T
When ordering gears, diametral pitch, tooth size, pitch diameter, gear size, pressure angle, tooth shape, and shaft size should be specified.
T
Worm-gear speed reducers are used to obtain speed reduction up to 100:1 with only one set of gears.
T
16.Locked-rotor torque is torque available at what speed for accelerating the load? a. 0 b. 1 c. 2 d. 3
a. 0
A(n) _______ is a plug with a hole that permits airflow inside a gearbox a. Breather b. Flow Plug c. Labyrinth Seal d. Elastomeric Sealing Lip
a. Breather
In worm gearing, _______ withstands high sliding velocity in contact with a steel worm better than other materials. a. Copper b. Aluminum c. Titanium d. Lead
a. Copper
18.What type of motor consists of two basic types including brush and brushless? a. DC b. AC c. Hybrid d. All of the above
a. DC
Which one of the following is used for lubrication? a. Grease b. Water c. Hydraulic fluid d. Ethanol
a. Grease
17.AC motor stators contain windings with two or more poles per phase. What type of poles are these? a. Magnetic b. Energetic c. Rodless d. All of the above
a. Magnetic
_______ gear speed reducers are used to obtain speed reduction up to 100:1 with only one set of gears. a. Worm b. Hypoid c. Helical d. Bevel
a. Worm
7. PM motors are offered in sizes from: a.1/4 to 5 HP b.3 HP to 5 HP c.5 HP to 10 HP d.10 HP and up
a.1/4 to 5 HP
Another source of information on gearing includes: a.Dudley's Gear Handbook b.Handey's Gear Handbook c.All About Gears d.All of the above
a.Dudley's Gear Handbook
2. Motors that operate on 60 Hz power systems are used in: a.Mexico b.France c.Germany d.Great Britain
a.Mexico
Which one of the following is an organization that establishes standards for both gears and enclosed drives? a. TSI b. ANSI c. DTN d. ANSH
b. ANSI
Where are internal gears typically used? a. Straight bevel gear systems b. Planetary gear systems c. Helical gear systems d. Spur gear systems
b. Planetary gear systems
1. The efficiency of these gears tends to be lower than other gear types: a. Helical b. Worm c. Hypoid d. Bevel
b. Worm
the synchronous speed of a 4 pole, 60 Hz motor is: a.3,600 b.1,800 c.1,200 d.900
b.1,800
4. Variable-torque loads include: a.Conveyors b.Fans c.Hoists d.Metal cutting machines
b.Fans
1. Another name for a 3-phase motor is: a.Step motor b.Polyphase motor c.Servo motor d.Single-phase motor
b.Polyphase motor
Worm-gear drives are referred to as: a.Speed drives b.Right-angle drives c.Left-angle drives d.Combination drives
b.Right-angle drives
These types of gears work well in corrosive environments: a. Helical b. Hypoid c. Plastic d. Internal
c. Plastic
8. General-purpose brushless DC motors are widely available with ratings up to about: a.1/3 HP at 1,800 rpm b.3 HP at 3,600 rpm c.20 HP at 1,800 rpm d.None of the above
c.20 HP at 1,800 rpm
In a Q8 A-HA-14 gear, the HA is the: a.Quality number b.Tooth thickness tolerance code c.Material designation d.Hardness designation
c.Material designation
3. Doubling motor load: a.Cuts motor heating in half. b.Doubles motor heating. c.Raises motor heating four times. d.Has no effect on motor heating.
c.Raises motor heating four times.
15.The majority of general-purpose, three-phase motors manufactured after are required to meet EPACT mandates. a. 1989 b. 1964 c. 1974 d. 1997
d. 1997
Which of the following gear design categories does not belong in the list? a.Spur b.Helical c.Worm d.Ground
d. Ground
_______ gears are like spiral gears except the teeth are not curved. a. Cycloidal tooth b. Internal tooth c. Hypoid tooth d. Skew tooth
d. Skew tooth
6. The difference between synchronous and actual rotor speed for a Design B motor is: a.20 percent at full load b.10-20 percent at full load c.5-10 percent at full load d.3-5 percent at full load
d.3-5 percent at full load
10. A typical DC motor option is a: a.Tachometer b.Blower c.Space heater d.All of the above
d.All of the above
Most enclosed drives are used to: a.Increase speed and output torque. b.Increase speed and reduce output torque. c.Reduce speed and output torque. d.Reduce speed and increase output torque.
d.Reduce speed and increase output torque.
22.Brushless motors have neither commutators nor brushes. a. True b. False
T
10.Locked-rotor torque is that torque available at zero speed for accelerating the load. a. True b. False
T
12.Polyphase motors are available in ratings from fractional to thousands of horsepower. a. True b. False
T
14.The majority of general-purpose, three-phase motors manufactured after October 24, 1997 are required to meet EPACT mandates. a. True b. False
T
18.There are two basic types of DC motors - brush and brushless. a. True b. False
T
19.Three types of wound-field DC motors include series, shunt, and compound wound. a. True b. False
T
