Motors Lvl 3 Flashcards
What 3 things are required for induction?
- ) Conductor
- ) Magnetic Field
- ) Relative Motion
T/F: Induction motors can spin at synchronous speed.
False. They can get close, but if the magnetic poles of the rotor and stator were synchronized, there would be no means of rotation
____ motors have no magnets, slip rings, or brushes.
Induction
How are synchronous motors different from induction motors?
In synchronous motors, the magnetic poles of the rotor and stator are locked and spin at the same speed.
What are the 3 types of relays for synchronous motors?
- ) PFFR
- ) Loss of Excitation
- ) Out of Step
What does PFFR stand for?
Polarized Field Frequency Relay
T/F: Synchronous motors are initially started as squirrel-cage motors.
True
____ resistors are used to dissipate any AC potential that builds up in the DC field winding in the rotor.
Discharge
The rotor of a(n) ____ motor produces a stationary magnetic field.
Synchronous
T/F: Any additional load added to a synchronous motor (within its rating) will not affect the speed of the motor.
True.
____ torque and maximum torque are the same value.
Pull out
____ torque and pull out torque are the same value.
Maximum
What are the 2 parts of an induction motor?
- ) Amortisseur Winding (squirrel cage)
2. ) Wound Rotor (DC field windings)
The bearings for high-speed rotors are located in the ____, which are bolted to the motor.
Endbells
____ motors are used to bring the rotor up to near-synchronous speed.
Pony
What happens when a synchronous motor slips out of synchronicity?
Protective relays shut it down before it destroys itself.
What does a PFFR do?
Simultaneously removes the discharge resistor and connects the DC field windings on startup.
T/F: Synchronous motors have little effect on the power factor of a facility.
True
What are the three circuits within a synchronous motor starting circuit?
- ) Power Circuit
- ) Control Circuit
- ) Exciter Circuit
The ____ circuit contains a discharge resistor that is a complete path for the current induced in the field windings.
Exciter
On startup, an ammeter may read up to ____% of running current.
700%
____ torque is the speed at which a squirrel cage motor starts to slow down when being overloaded.
Breakdown
The difference in angle between the stator’s magnetic poles and the rotor’s magnetic poles is called the ____.
Torque Angle.
A synchronous motor that is ran with no load just for power factor correction is called a ____.
Synchronous Condenser
____ braking is when a resistor is used to dissipate energy from a still-spinning motor by using it as a generator, and a resistor as a load.
Dynamic
____ braking is when the inertia of the still running motor is used to generate power which is used.
Regenerative
T/F: Brake solenoids for friction brakes should be connected to the motor power circuit.
True, this way, when the motor loses power, it is stopped when the solenoids release.
____ is when relays reverse motor connections to reverse rotation and the motor develops a countertourque.
Plugging
Plugging creates high ____ and heat.
Current
____ braking is the only braking method that can stop in the event of power failure.
Friction
____ braking provides an immediate stop in an emergency situation.
Electric
An ____ system prevents two sets of contacts from being connected to the same load at the same time, to prevent damage.
Interlock
What are the 3 types of interlocking?
- ) Mechanical
- ) Pushbutton
- ) Electronic
____ breaking causes the same amount of heat as starting at full voltage.
Electric
____ braking is the only braking style that won’t bring the motor to a complete stop.
Dynamic
____ motors have two windings, the brushes move across the windings to change the voltages.
Shrage
T/F: A separate starter is required for each speed of a consequent pole motor.
True
____ motors usually have two speeds, one being half the other.
Consequent Pole
What are the 3 logic functions when controlling a consequent-pole motor?
- ) Compelling
- ) Accelerating
- ) Decelerating
When you push the ‘High’ Button on ____ logic functions, it starts the motor on low before transitioning to high.
Accelerating
____ logic functions requires the operator to start the motor on low before transitioning it to high speed.
Compelling
The ____ section of an adjustable speed driver controls the speed and torque by controlling voltage, frequency, and current.
Inverter
The inverter section of a VFD controls what three things?
- ) Voltage
- ) Frequency
- ) Current
What are the three parts of VFD?
- ) Converter (rectifier)
- ) DC bus
- ) Inverter
Damage may occur to an AC motor if supply voltage is applied ___% above or below the rated nameplate voltage.
10%
The frequency of the voltage used to control the motor is called the ____ frequency.
Fundamental
The ____ frequency is the modulated frequency coming out of the inverter.
Carrier
Drives for ____ motors are the most complex.
Compound-Wound
The ____ frequency is often raised above human hearing to eliminate noise.
Carrier
____ drives have greater control over speed and torque than a standard inverter drives.
Vector
____ ____ inverters are the only drives that can run multiple motors at one time.
Variable-Voltage
A motor hooked up in ____ will have fewer poles, and rotate faster.
Series
A motor hooked up in ____ will have more poles, and rotate slower.
Parallel
____ bearings have no moving parts. (other than the shaft)
Friction
____ bearings have either steel balls or rods that move within the bearing.
Rolling-contact
____ is the general wear of rolling contacts as metal pieces flake away the surfaces in contact, leaving a roughened surface.
Spalling
____ damage is bearing damage due to axial force.
Thrust
____ bearings are quieter, less expensive, have less wear, and can take heavier loads than other types of bearings.
Friction Bearings
The inner and outer ____ are the the tracks that contain the cage for ball bearings.
Races
____ is damage caused by chemical reactions between the lubricant and the bearings.
Surface Reaction
____ is a normal condition that just comes from normal wear and oxidation.
Fretting Corrosion
____ bearings can handle both axial and radial loads. Special Friction bearings also can.
Tapered
____ and ____ is damage caused by electrical current flowing through a bearing.
Pitting and Fluting
Cylindrical bearings are not made to handle ____ force.
Axial
____ bearings bear directly on the rotating shaft.
Needle
T/F: Bearings fail more often due to poor installation than bearing failure.
True
The best heating method for expanding a bearing is (a) ____.
Hot oil bath
T/F: Bearing installation is more difficult than removal.
False, It’s easier to heat and set a bearing initially than try to slip/press it off.
____ damage is dents on any component of a bearing due to dropping/hitting/pressing.
Brinell
____ close spaces between moving parts of moving and stationary components.
Oil Seals
A common mistake when greasing bearings is ____.
Over-lubricating
____ Gears have teeth that are NOT parallel to the shaft.
Helical
____ gears have bevels and are used when two shaft axes intersect.
Bevel
A(n) ____ clutch uses a magnetic field to couple a motor to a load.
Eddy Current
____ gears are the most common in industry.
Spur
A(n) ____ V-belt has a smaller cross section and a higher profile, giving it more friction with the sheaves.
Narrow
A(n) ____ belt has teeth on it so that it cannot slip.
Timing
What are the three types of sprockets?
A (No Hubs)
B (One Hub)
C (Two Hubs)
A(n) ____ is a grooved wheel to hold a v-belt.
Sheave
A(n) ____ is a coupling that can connect or disconnect a load while a motor is running.
Clutch
What are the four different types of Soft Footing?
- ) Parallel
- ) Angular
- ) Springing
- ) Induced
____ soft foot is when external forces are applied to the motor.
Induced
What is the phonetic device Derek told us to remember, that helps with remembering what order to align motors in?
VAP HAP
(Vertical - Angular - Parallel)
(Horizontal - Angular - Parallel)
What does MTBS stand for?
Machine to be shimmed.
What does SM stand for?
Stationary Machine
Why is the motor almost always the MTBS?
Because it’s almost always easier to move/adjust the motor than to move the machine it’s running.
____ is when the bolt head of a mounting bolt disfigures the washer.
Doweling
A(n) ____ circuit occurs when current leaves its normal current path and travels to the frame of the motor.
Ground Fault
____ is the most common cause of motor failure.
Overloading
____ is when one of the three-phase leads drops out and no longer delivers voltage to the motor.
Single-Phasing
____ is the most extreme example of voltage imbalance.
Single-Phasing
Belt deflection should equal about ___” per inch of span, the span being measured from center to center.
1/64”
____ detect insulation failure on wires by measuring resistance values of the windings.
Megohmmeters
____-____ starting is the most modern example of reduced voltage starting.
Solid-State
____ are the fastest wearing components of a DC motor.
Brushes
____ material is a medium in which an electric field is maintained with little or no outside energy supply.
Dielectric
Split-Phase motors have their start winding removed by a(n) ____ as the motor accelerates.
Centrifugal Switch
A dual voltage, wye connected motor has __ separate stator windings.
4
Generally, a dual voltage, delta connected motor has __ separate stator windings.
3
Terminals __ and __ are always the connection leads for shunt windings.
F1 and F2
