Ch 34 Single-Phase AC Motor
In a potential start relay how is the start relay coil connected to the start coil
they are connected in parallel
What factors determine the starting torque of a split phase motor
The strength of the magnetic field in the stator. Strength of the magnetic field in the rotor. The phase angle between the start windings and the Run windings
What is the name of the electronic component used in a solid state relay
Thermistor
what principle does the split phase Motors operate on
a rotating magnetic field
what would be some examples of why you would need a synchronous motor
clocks, timers and recording instruments
What are the two types of multi-speed motors
consequent Pole. Capacitor start capacitor run
Most split phase induction motors have run windings with a resistance of 1 to 4 ohms. however the multi Speed Motor has run windings of what resistance
10 to 15 ohms
what is the speed of a Holtz motor
1200 RPM
Multi speed motors
1625. 1500. 1350. RPMs
what is the speed of a Warren motor
3600 RPM
What happens to the Armature windings in a repulsion type motor once a magnetic field is induced into the pole pieces of the stator
Current begins to flow through the Armature windings
on what principle does the solid state relay work
Heat
Describe the characteristics of a synchronous motor
RMF RPM equals RPM of shaft
What are the three types of split phase Motors
Resistance start induction run. Capacitor start induction run. Capacitor start capacitor run
What are two types of single-phase synchronous Motors
Warren and Holtz
What are the two types of repulsion start induction run motor
brush riding. bush lifting
How can the speed of a repulsion motor be varied
by changing the ac voltage Supply
How do you change the direction on a split phase motor
by changing the leads of the start winding
what should you not do to protect a capacitor start induction run motor
do not start this motor more than eight times in one hour
If a dual voltage split phase motor only has one start winding how could the leads be labeled
either T5 T6 or T5 T8
What type of loads do multi-speed Motors typically run
fans and blowers
How are the Run windings and start windings in a split phase motor connected
in parallel
does a repulsion type motor have a start winding
no repulsion type Motors only use a run winding
Capacitor in a capacitor start capacitor run split phase motor is usually what
oil filled
what is the operating principle of a synchronous motor
operates on a rotating magnetic field using shade poles in the stator
characteristics of a repulsion induction motor
same as a repulsion motor except a squirrel cage rotor is added to the Armature
What type of rotor does a split phase motor have
squirrel cage
a shaded pole induction motor uses what kind of rotor
squirrel cage
How Is a shaded pole induction motor different from a split phase induction motor
the Shaded pole induction motor as no start winding
what is slip
the rotating magnetic field RPM minus the shaft RPM equals the slip
What two windings are used to create the split phase in a single phase motor
the start winding the Run winding
Describe how the potential start relay works
when power is applied to the circuit the potential start relay closes and Power is being supplied to the start relay. Once the motor reaches 75% of full speed the start relay opens and the start "relay" coil becomes De-energized. The start winding continues to receive power from the Run capacitor
What creates the rotating magnetic field in a split phase motor
when the current flow in the Run windings are out of phase with the start windings
In a resistive-start Induction-run split phase motor what is a typical phase angle
35 to 40%
repulsion type Motors contain the same number of brushes and stator poles. what are the most common number of stator poles in a repulsion motor
4, 6 or 8
What is the ideal phase angle for maximum torque in a split phase motor
90 degrees out of phase
If not hermetically sealed what type of start capacitor would be added to a capacitor start capacitor run split phase motor
A Centrifugal Switch
What are the two ways to connect the compensating windings in the Universal motor
Conductive (Series). Inductive (Shortened Together)
3 types of relays used in a hermetically sealed split phase motor
Hot wire Relay. Current relay. Solid state relay
If a dual voltage split phase motor has to start windings how would they be labeled
T5 T6 T7 T8
Compare a phase angle with power factor
a phase angle of 90 degrees would equal a power factor of 1
How does a repulsion start induction run motor start and run
a repulsion start induction run motor starts like a repulsion motor and runs like a squirrel cage motor
On what principle does a hot wire relay function
a resistance wire heats up. First causing the contacts to close on the start winding. If the resistance of the wire continues to heat an overload relay will open to stop the motor from being damaged
In the brush riding repulsion start induction motor what type of commutator is used
axial commutator
Why are Shaded-Pole induction Motors popular
because of their Simplicity and long life
where would the main run winding be in a multi-speed motor
between the common and the high-speed connection
how would you reverse the direction and a repulsion type motor
if the brushes are set at an angle of 15 degrees in front of the stator Pole the motor will operate in a clockwise Direction. If the brushes are placed at a 15 degree angle behind the poles of the stator the motor will operate in a counterclockwise Direction
What is a repulsion type motor's Rotor called
it is called an Armature because it has a slotted metal core with winding through the slots
What is the operating principle of the Shaded pole induction motor
just like split phase Motors the principle of the Shaded pole induction motor is a rotating magnetic field
Describe run windings in a split phase motor
larger wire placed near the bottom of the stator
what are common values for slipped
less than 2%. 2 to 5%. Greater than 5%
What would happen if there was no mechanical load connected to the shaft of a repulsion motor
motor race at a very high speed
When AC reaches Peak voltage what is the induced voltage of a shaded coil
no
How could you increase the starting torque of a capacitor start capacitor run split phase motor
place a second capacitor in series with the start windings
If a capacitor start capacitor run motor must be hermetically sealed what type of additional start relay would be used
potential start relay
What is the operating principle of a potential start relay
potential start relay senses voltage in the start winding
Describe the relationship between the stator fields and the rotor fields in a split phase motor
power comes into stator windings and induces a rotating magnetic field in the rotor bars. The induced voltage is in phase in the stator windings. And the current in the rotor is 90 degrees out of phase with the stator
What is the operating principle of a repulsion type motor
repulsion type Motors operate on the principle of like poles repel.
How would you change the direction of a dual voltage split phase motor
reverse the start windings
how would the Run windings be connected in a dual voltage split phase motor if operating on low voltage
run windings would be connected in parallel
How are the brushes of the repulsion type motor different from the brushes of a DC motor
the brushes are shorted together. the brushes function to provide a current path through the Armature.
What advantage does a capacitor start induction run split phase motor have over a resistant start induction run motor
the capacitor start has a much greater starting torque
And a brush writing repulsion start induction run motor what happens to the motor when 75% of full speed boat is reached
the copper segment swings out and makes contact with the commutator. the motor then operates like a squirrel cage motor
Describe the current flow through the in a split phase motor
the current flow through the Run winding LAGS the applied voltage do to inductive reactance
What determines the direction of rotation of a split phase motor
the direction is determined by the rotation of the magnetic field
In a shaded pole induction motor what happened to the magnetic lines of flux when voltage is induced
the magnetic lines of flux begin to increase
What happens to the speed of a multi -speed motor when load is added
the motor slows down
which type of motor has the highest starting torque of any single phase motor
the repulsion type motor
When ac voltage starts to decrease what happens to the magnetic lines of flux in the Shad coil
the shade coil creates a current that opposes the magnetic flux
how is a capacitor start capacitor run split phase motor different from the induction run Motors
the start winding remains energized at all times
In a dual-voltage split phase motor how are the Run windings and the start windings connected
the start windings are always connected in parallel to the Run windings
why does the Armature in a repulsion motor rotate
the two magnetic fields of the stator and the Armature oppose each other
when you split the current flow in a split phase motor what happens to the voltage
the voltage becomes 90 degrees out of phase
What are advantages of a solid state relay
they are more reliable and less expensive
how would you connect the Run windings on a high voltage split phase motor
they would be connected in series
the capacitor is connected in series with the start winding for what reason
to provide continuous leading current
describe what happens when a brush lifting repulsion start induction run motor reaches 75% of the full operating speed
weights are mounted to the front of the Armature period at 75% of Speed The weights swing out and cause the brushes to no longer be in contact with the commutator. this will create a longer life and a quieter motor
What happens when you place a capacitor in series with the start windings in a split phase motor
you can get a phase angle of 90 degrees. this will create the highest starting torque possible
How do you split the phase on a single phase motor
you have to split the current flow through two separate windings
Why is a shaded coil induction motor considered to be non-reversible
you would have to change the whole pieces in the stator
What is the power factor of a capacity start capacitor run motor
.98 - .99 ( A perfect PF would equal 1)
The brushes that ride on the commutator of a repulsion type motor will affect the torque . what angle creates the highest amount of torque in a repulsion motor
15 degrees before or 15 degrees after the stator Pole
What principle does the current relay function
A magnetic field that is controlled by current flow through a coil connected in series with the Run winding. When the thermostat closes, current begins to flow through this coil, which becomes magnetized, and closes the contact on the start winding. This reduces the current flow in the Run winding and the magnetic field decreases and the start winding contact open
In a dual-voltage split phase motor how are the Run windings labeled
T1 T2 T3 T4
What two factors determine the speed of a split phase motor
The number of stator poles. The frequency of the applied voltage
Multi speed motors have what kind of running torque
a high running torque is maintained at different speeds
what happens when AC power is induced into the stator windings of a repulsion type motor
a magnetic field in the poles of the stator is created that has alternating polarities
What determines the speed of a shaded pole induction motor
frequency of the induced voltage. Number of stator poles ( usually 4 to 6)
When the rotary switch and a multi-speed motor is adjusted from medium to low
inductance is in the Run windings causing a decrease in the current flow causing a decrease in torque causing a decrease in speed
What happened when you switch from the high speed setting to the Medium Control winding in a multi Speed Motor
inductive reactance increases which causes limited current flow. this decreases the magnetic field which causes less torque. Speed of the motor decreases. this is the amount of slip
what is the operating principle of a repulsion type motor
it is and induction motor. it does not operate on the principle of a rotating magnetic field
what type of commutator does a brush lifting repulsion start induction run motor used
radial commutator
What is an advantage of a repulsion induction motor over the repulsion motor
repulsion induction motors have the same high starting torque but a better speed control. very good speed control between no load and full load
Name three basic types of repulsion type Motors
repulsion motor. Repulsion start induction run. Repulsion induction motor
Describe the properties of start torque and run torque of a shaded coil induction motor
start torque and low running torque
What do the brushes of a repulsion type motor make contact with
the brushes make contact with the surface of the commutator bars
what is the advantage of a capacitor start capacitor run split phase motor
they have hi starting and running toward and run quietly and with high efficiency
How are the Run windings of a multi-speed motor connected
they are connected in series and use inductance to control speed
What are the windings in the Armature of a repulsion type motor connected to
they are connected to the commutator bars
What characteristics describe a start winding in a split phase motor
they are small wires placed near the top of the stator
