Test 1 Magnetism, Motors, Generators Flashcards
How do you de-magnetize magnetic material
Hitting it with a hammer, and/or heat
Magnetic inductors oppose a change in?
Current
1 Horsepower (HP) is equal to how many Watts?
746W
What DC motor has the best Torque Characteristics
Series motor
What is the name of a natural Magnet
Magnetite/lodestone
What type of voltage is in a rotating generator
AC voltage
Other DC motor types?
Permanent Magnet
DC servo
Brushless
What is the opposing force in a motor?
CEMF (counter electromotive force)
What shape are field windings?
Square
Unlike poles do what?
Attract
Like poles do what?
Repel
Electromagnetism occurs when current passes through?
The Conductor
What does the Commutator do?
Changes AC to DC
And
Maintains the proper polarity of the dc voltage
Brushes ride against what component?
The Commutator
How can you compensate for armature reaction
• Compensating Windings
• Adjust brushes to compensate for new point of neutral plane
• Interpoles
Another term for armature?
Rotor
The amount of voltage induced in in a conductor is affected by
• Turns of wire
• Strength of magnetic field
• Speed of cutting action
The time constant for voltage to be fully induced?
5 times
How to change the direction of the armature
Reverse the connections (change the Armature leads)
In the right hand rule, what does the middle finger indicate?
Direction of Current
What current causes excessive heat in the metals core material
Eddy current
Lenz’s law states what?
The direction ofInduced current will oppose the motion that caused it
Interpoles can be found in between?
Between the main poles
How is the shunt field connected to the armature
In parallel
2 methods to prevent voltage spikes
Diodes and Resistors
What is permeability?
The ability to conduct magnetism
Large spikes of voltage can be used for what?
Cow Fences
Induction occurs when what passes through the magnetic field?
Conductor
Separately excited shunt field is a shunt field that has
A different power supply
Motors use what to rotate the armature?
Attraction and repulsion
How do you control field excitation in a series shunt field motor?
Rheostat (variable resistor)
Losses in a motor are?
• Windage Losses
• I^2 R
• Bearing Friction
3 factors that affect output voltage of a DC generator
Conductor loops in the armature
Armature speed
Magnetic field strength
Easily magnetized materials are known as?
Ferromagnetic
What is it called when magnetism is still left in a motor that has been shut off?
Residual magnetism
Difference between generator and motor?
Generator: Converts mechanical energy into electrical
Motor: Converts electrical energy into mechanical
What is coercive force?
A materials ability to stay magnetized after the magnetic force is removed
What is flux density?
The magnetic field strength of the lines of force
What is the north poles true polarity?
South polarity
How can you produce AC voltage?
Slip rings
Unit of measurement for an inductor?
Henry
Compound Generator is made up of _______ Shunt and ______ Shunt.
Long and Short
Left hand rule, what does the middle finger signify
Current
What is it called when there is 0 Volts in the commutator?
Neutral Plane
When the North Pole and South Pole don’t line up with the true magnetic poles
Declination
How is a series motor connected?
In Series
