WorksheetsUnit-5 Part-2
Total questions: 41
Worksheet time: 21mins
Why the core is laminated in the universal motor?
Reducing torque and speed
Reducing energy loss
Increase speed
Running smoothly
What separates each of the commutator copper segment in universal motor?
mica
spring
bearing
end rings
How to know the brush grade current carrying capacity
Talk the operator
Check the brush damager
Manufacture manual
Nameplate
In universal motor What part is attached either to the brush holder this pushes the curved brush face?
Brush holder
Commuter
Spring
Cap threads
branch circuit conductors supplying a single motor at full-load (continuous duty) shall have__________________
100% of the motor full-load current rating
50% of the motor full-load current rating
125% of the motor full-load current
100% of the motor no full load current
The current carrying capacity (ampacity) if a branch circuit conductors supplying a single motor shall be _________-
100% or less of the motor full-load current
100 % or not less of the motor full-load current
125% or not less of the motor full-load current
125% or not less of the motor full-load current
NEC article 430-32 © states that any motor of 1Hp or less than started automatically from high starting current by
A circuit breaker
A fuse
An overload device
A protective relay
On a capacitor –Start motor remember that the capacitor must be
Ensure all mobbing parts are stationary
Power supply circuit is de-energized
Lockout and hold tags are followed
Discharged before removing any connections
The test device used to measure the running current of a motor is called
Digital ammeter
Tachometer
Clamp-on meter
AVO meter
The device used to measure the speed of the motor is known as
Clamp-on meter
Tachometer
Proximity tester
Generator
What protects and holds the bearing on a squirrel-cage motor?
rotor assembly
bearing
end shield
end rings
When installing motors what will be used to adjust and align the motor?
a)
flat plates
shims
spring washer
bolts and nuts
When you connect, the motor prior to energizing you must?
Turn the rotor by hand checking the rotor turn freely
Operate the motor to the power supply.
Attaché the rotor shaft to the machine
Turn on the power supply
The main possible cause the capacitor–start motor fails to start is
Circuit breaker tripped
Broken fan blade
Unbalanced rotor
Loose part
The main possible cause the capacitor – start the motor the motor run noisily is
Low voltage
Excessive load
Incorrect capacitor value
Bearings requires lubrication
What possible cause the capacitor–start the motor runs slower than normal?
Low voltage
Winding short circuit
Circuit breaker tripped
Loose part
What possible cause the capacitor – start the motor the circuit breather trips when motor energized?
Low voltage
Winding short circuit or grounded
Incorrect capacitor value
Bearings requires lubrication
When replacing the capacitor of a capacitor – start motor, the replacement capacitor must have the same
Voltage rating or higher than the original capacitor
Capacitance or higher than the original capacitor
Frequency or higher than the original capacitor
Manufacturer
When replacing the capacitor of a capacitor–start motor, the replacement capacitor must have the same
Voltage rating only
Capacitance as original capacitor
Frequency or higher than the original capacitor
Manufacturer
When replacing the capacitor of a capacitor – start motor, the replacement capacitor must have the same
a.
Voltage rating or lower original capacitor
Capacitance or higher than the original capacitor
Frequency as the original capacitor
Manufacturer
If a universal motor fails to start, the possible cause could be
a.
Loose bolts and screws of motor parts
Brushes in poor contact with the commutator
Worn and noisy bearings
The motor is under load
What happens to a universal motor if it has worn bearings?
Motor will fail to start
Motor will run noisily
Circuit breaker will trip
All of these
When a universal motor runs with a noisy sound, the possible cause will be
Bearing are worn need lubrication
A fuse has blown when the motor has started
An open occurred in the failed winding
The motor is under load
Why is the jog start test performed on motors?
to check the motor will not trip
to check its direction of rotation
to check the motor will not overheat
to check the motor run without noise
Poor commutation causes
Burning and wear of brushes
Motor will fail to start
Motor will run noisily
Circuit breaker will trip
What do you do to correct streaking of the commutator?
Recondition the commutator by specially trained personnel
Clean the commuter and replace the brushes
By washing and reaming
Use of copper drag to transfer grooving
What do you call the DC commutator fault if the commutator cause of low brush pressure causing high resistance are called?
Sparking
Streaking
Threading
Grooving
What do you call the DC commutator fault if the commutator. cause heavy wear on the commutator is called
Sparking
Streaking
Threading
Grooving
1. What do you call the DC commutator fault if the commutator causes fine lines cut into the surface of the commutator, this problem is called
Sparking
Streaking
Threading
Grooving
What do you call the DC commutator fault if the commutator surface has burned spot?
heavy slot-bar marking
capper drag
pitch bar marking
threading
The DC commutator motor fault that usually forms at the trailing edge of the segment bars and can cause flash-over/arcing
copper drag
pitch-bar marking
heavy slot-bar marking
loose commutator segment
What do you call the DC commutator fault if the commutator, bar is etched (removed) rather?
Pitch-bar marking
Heavy slot-bar marking
Copper drag
Streaking
A test used to check the segments are all at the same height is called
Loose commutator segment
High mica test
Commutator run out test
Brush rigging
When the brushes start to make contact with the mica, this problem is called
Loose commutator segments
High mica
Commutator run out
Brush rigging
How do you repair and chips or cracks in insulation?
by shaping and forming
applying a small amount grease
by removing sleeves and spacers
coat with electrical varnish
How do you remove carbon dust build-up inside a motor?
applying a small amount grease
using vacuum cleaner
by removing the sleeves and spacers
coating with electrical varnish
Before fitting new brushes you must shape them to fit the commutator curvature is called
Brush rigging
Marking
Arcing
Seating
Why seating brushes?
excessive arcing
minimize arcing
grounding
short circuit
When maintaining a DC motor, how do you find the correct grade of brush to install
Check the brush website
Look in the NEMA hand book
Look in the manufacturer’s manual
Look in the NEC book
When replacing brushes, if one burse damage you must
Replace only the damage one
Brushes can’t be replaced
Replace the whole set of brushes with holder
None of these
Why must remove any rough edges on the brush holders?
To fit the commutator curvature
To have a nice shape
To have excessive wear
To slide easily into the holder
