DC Motors Flashcards
What does a commutator do?
It applies an electric current to the windings.
What are windings?
They are conductive wires wrapped around a magnetic core; they provide a path for current to flow to create the magnetic field to spin the rotor.
The rotor of the DC motor is made of…
coils of wire
What does Maxwell’s Right Hand Grip Rule indicate?
It shows the direction of a magnetic field around a conductor
What will lines of magnetic flux never do?
They will never cross (they will either bunch together or cancel each other out)
Using Fleming’s Left Hand Rule, what does each digit indicate?
Thumb = Motion (of conductor)
First Finger = Field
Second Finger = Current
What is Back EMF?
It’s an induced EMF that is opposite in polarity to the EMF that is being applied to the conductor
The amount of torque produced by a motor is dependent upon what two things?
- Strength of the magnetic field
- Size of the current
List the 3 classifications of DC motors.
- Series,
- Shunt,
- Compound
What must the carbon brushes be fixed in the same position as? And why?
- Magnetic Neutral Axis (MNA)
- To stop sparking at the brushes (when the gap in the two halves of the split ring passes the brushes)
When the armature has current flowing through it, a _____________ is established.
magnetic field
The magnetic field of the armature will distort the field winding’s magnetic field and move the ___________
MNA (Magnetic Neutral Axis)
Distortion of the MNA causes the brushes to be misaligned, causing ______________ at the brushes.
sparking
What are inter-poles, where are they fitted and what do they do?
- They are poles, similar to the main poles, but smaller
- They are situated in between the main poles
- They assist in giving spark-less commutation by neutralising the effect of armature reaction
