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For what reason is a univerdal motor called universal?
Because it has the ability to run on either A.C or D.C current
State the typical power rating of universal motors
Between 3-550 Watts
Explain how change of direction on a universal motor can be acheived?
Interchange either the armature leads or the field leads
What is housed in the stator?
Silicone-Iron laminations with slots containing field coils
How nis the rotor constructed?
A simple squirrel cage arrangement made up of copper bars and end plates, brazed together
Why are the bars of the rotor skewed?
To prevent noise
Why is a centrifugal switch needed?
So that the start winding can be dissconnected as soon as it has served its function
Why is it called the split-phase motor?
Because the phase needs to be split and displaced
How is phase displacement, to simulate stator field rotation, obtained?
Two pairs of poles are wired in parallel to the supply and are placed around the circumfrence of a stator housing. One pair of ploes represents the start winding and the other pair represents the run winding. The start winding has fewer poles than the run winding. Therefore the inductive reactance/resistance ratios of the two windings differ, causing a phase displacement between the start winding current and the run winding current
What is the main difference between a split phase motor and a capacitor start motor?
The two motors are similar in construction but the capacitor start motor has more turns of finer wire in its start winding and has a capacitor in series with its start winding
What is the function of the capacitor in a capacitor start motor?
To produce a torque that is great enough to start a motor which requires a greater starting torque than that of a normal split phase motor
How can reversal be obtained in a capacitor start motor?
By changing the connections to either the start winding or the run winding. NOT BOTH
What is the essential constructional differnece between a capacitor start motor and a perminantly split capacitor motor?
The capacitor start winding has more turns of finer wire than the start winding of a split phase motor
What is the typical power output of a shaded pole motor?
What makes this motor attrative for its use and purpose?
Its simplicity and robust nature of its construction
What type of rotor does it have?
The squirrel cage one
Can the shaded pole motor be reversed?
Only by turning the entire motor around can a reverse feature be obtained
Describe the pole of a shaded pole motor
Each pole has a shortened coil of one turn placed around about one third of the pole
Why dioes the shaded pole motor run hot around the shaded rings?
Because the shaded rings carry particularly high current
What is a motor enclosure?
A strucural device to protect the motor agianst it environment
Name 4 types of enclosures
- -Screen protected
- -Drip proof
- -Totally enclosed
- -Flame proof
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