The universal motor can operate on both AC and DC power sources. It has series-connected stator and rotor windings, with the rotor windings connected to commutator bars and brushes. The commutator switches the direction of current in the rotor coils to enable rotation when powered by either AC or DC. It is also known as an AC series motor or AC commutator motor.

1. Universal motor
Presented by:
Sanjeet kumar
Registration No.-1308143
Branch: Electrical & Electronics Engineering

2. UNIVERSAL MOTOR
• Motor that can be used with a single-
phase ac source as well as a dc source of
supply voltages are called universal
motor.
• The stator and rotor windings of the motor
are connected in series through the rotor
commutator.
• The universal motor is also known as an
AC series motor or an AC commutator
motor.

3. MOTORS 3
Universal Motor

4. Universal Motor
• Series-connected
– Rotor and Stator are
connected in series
• Operates on either ac
or dc
MOTORS 4

5. Equivalent Circuit
ECE 441 5

6. A Closer Look
ECE 441 6
Armature
(Rotor)
Field Winding
Field (Stator)

7. ECE 441 7
The Commutator Bar and Brushes are a switch that
reverses the current in the armature coil as it rotates

8. Check the Direction of Rotation
ECE 441 8
Force on conductor B is
upwards, rotation is counter-
clockwise (CCW)
Flux
“Bunching”
+Positive Half-
Cycle+

9. Opposite Half-Cycle
ECE 441 9
Force on Conductor B is
upwards, rotation is counter-
clockwise (CCW)
Flux
“Bunching”
-Negative Half-Cycle-

10. Other Considerations
• How do you reverse the direction of rotation?
– Reverse the direction of the current in either the field or in the
armature, but not both!
• How do you control the speed of the motor?
– Reduce the voltage applied to the motor
• Use an autotransformer or SCR/Triac
• This reduces the armature current, reducing the torque, reducing the speed
• Applications
– Portable power tools
– Small appliances
ECE 441 10

11. Presented By:
Sanjeet Kumar
sanjeetkumar2101@gmail.com
+91-8968143473