Name: Arun Kumar R
Designation: Vocational Trainer
Institution name: Government Higher
Secondary School, Kuttalam,
Mayiladuthurai.
Vocational subject name: Basic
Standard: XI
Electrical Engineering
UNIT No : 08
Sub Category: 01
Title: Change the direction of the given AC Single phase capacitor motor.
Objective:
1. Students will be able to know the Connection of Single Phase Induction Motor
& Capacitor.
2. Students will be able to change the direction of rotation of the AC Single
Phase Motor.
Things to know:
1. AC Single Phase Induction Motor has two windings, Starting & Running Coil.
2. To connect the capacitor, it is essential to find the Starting & Running Coils of the
Motor.
3. The coil that has the higher resistance is Starting Coil & the other coil is Running
Coil.
4. For changing the direction of rotation of the motor, the terminals of the running coil
can be interchanged (or) the terminals of Starting Coils can be interchanged.
Safety measures:
1. All the Students should wear Shoes before doing Practical.
2. Students can do practical only after getting permission from the Vocational
Instructor.
3. Students should perform this practical only in front of the Vocational Instructor.
4. Electrical supply should be turned off while connecting Wires & other equipment.
5. Avoid Contact with live wire while performing practical.
6. Proper Tools & Equipment with necessary Insulation should be used for Practical.
Application:
Many of the motors used in Water Pumps, Ceiling Fan, Table Fan & Exhaust Fan
etc., are reversible, that is depending upon the connections made in the motor, it can
rotate forward or backward. Even though rotating in backwards, desired output will be
received but this type of Misuse will lead to catastrophic failure of Motors. Hence, in order
to improve the life time of the motor, it is essential to Note the Direction mentioned in the
Label & maintain the motor.
These motors are mainly used for low noise and high starting torque applications
1. Compressors
2. Pumps
3. Air Conditioners
4. Refrigerators.
Tools and equipment required:
Sl. No
Name of the
Specification
Quantity
Tool/Equipment
1
Single
phase
Induction
1
Motor.
2
Capacitor.
1
3
Digital Multi-meter.
1
4
Insulation tape.
-
1
Procedure:
Identification of Starting & Running Coils:
1. Before Connecting Capacitor to a Single Phase Induction Motor, it is essential to
identify the Starting coil & Running Coil of the Motor.
2. To identify the Starting and Running coil of the Motor, Set the Rotatory switch of the
Multi-meter at the Continuity mode & connect one end of the Multi- meter to any
one of the four terminals (2 terminals – Starting Coil & 2 terminals – Running Coil)
of the Motor.
3. Check for the continuity by connecting the second end of the Multi-meter to other
three terminals, one after the other.
4. Buzzer Sound will surely Occurred when connecting the Multi-meter to any one of
the three terminals. If the buzzer sound occurs, note the value of the Resistance
that will be shown in the Multi-meter and name it as V1. (Note: As of now, Identified
coil may be either Running coil (or) Starting coil.
5. After observing the Resistance, disconnect the Multi-meter & connect it across the
other two terminals of the Motor & note the value of Resistance displayed in the
Multi-meter and name it as V2.
6. Case 1 – If, V1 > V2, then the coil that has the Resistance (V1) is the Starting Coil &
the coil that has the Resistance (V2) is the running coil.
7. Case 2 – If, V2 > V1, then the coil that has the Resistance (V2) is the Starting Coil &
the coil that has the Resistance (V1) is the running coil.
Connection of Single Induction Motor with Capacitor:
1. After the Identification of Starting & Running Coils, name the two terminals of the
starting coils as S1 & S2 and name the two terminals of the Running coils as R1 &
R2. Connect R1 terminal of the Running coil with S1 terminal of the Starting coil,
insulate the Joint & name it as Common.
2. Connect R2 of running coil with 1st terminal of the capacitor (name the joint as A1)
and connect the 2nd terminal of the capacitor to S2 of the starting coil (name the
joint as A2), insulate both joints using the insulation tape.
3. Connect the Phase terminal of the supply to the Joint A1 and connect the Neutral
end of the supply to the Joint Common. (Note: This connections should be done
only after turning OFF the power supply).
4. After making the entire connections, Vocational Instructor will have to verify the
connections and after getting permission from the Vocational Instructor Electrical
Supply will be Turned ON.
5. Observe the Direction of the rotation of the Motor and note it. (Note: It may be
either Clockwise (or) Anti Clockwise).
6. After observing the direction of the rotation of the Motor, Turn OFF the power
Supply, slowly remove the Insulation of the Joints A1 and Common.
CAUTION: Care should be taken while removing the insulation of the
capacitors, because the capacitor may not be discharged, hence it essential to
remove insulation for one terminal of capacitor and later remove the
insulation of the other end of the capacitor.
7. After removing the insulation & joints of A1 & Common, inter change the
connections of R1 & R2. Make other connections as said earlier.
8. After making the entire connections, Vocational Instructor will have to verify the
connections and after getting permission from the Vocational Instructor Electrical
Supply will be Turned ON.
9. Observe the Direction of the rotation of the Motor and note it.
10.
Case 1: If the direction of the rotation of the motor is Clock wise before
interchanging the connections of R1 & R2, then after interchanging it will be in Anti
Clock Wise in Direction.
11.
Case 2: If the direction of the rotation of the motor is Anti-clock wise before
interchanging the connections of R1 & R2, then after interchanging it will be in
Clock Wise in Direction.
Additional information:
The above said practical experiment is applicable for the motors in Motor Pump,
Ceiling Fan etc.,
Pictures to be inserted for this exercise:
Conclusion:
1. Connection of Single Phase Induction Motor & Capacitor has been Done
Successfully.
2. The Direction of rotation of the AC Single Phase Motor has been Changed
Successfully.
Summarization:
1. Many of the motors used in Water Pumps, Ceiling Fan, Table Fan & Exhaust Fan
etc., are reversible, that is depending upon the connections made in the motor, it
can rotate forward or backward.
2. To connect the capacitor, it is essential to find the Starting & Running Coils of the
Motor.
3. The coil that has the higher resistance is Starting Coil & the other coil is Running
Coil.
4. For changing the direction of rotation of the motor, the terminals of the running coil
can be Interchanged.
Student activities:
Students can be asked to prepare a small Exhaust Fan which can be switched to
run on dual directions.
Simple assessments:
Students can be given 2 to 3 faulty Single Phase Induction Motor and will be asked
to find the Resistances of the coil & to identify the Starting and Running coils of each
faulty motor.
Guest lecture suggestions:
Service Technician in the field of Trouble shooting & fault rectifying the Ceiling Fan,
Water Pump etc., can be requested to do Guest Lectures.
Industrial/Field visit suggestions:
Students can be taken to the nearby Electrical Service centers, in which the
resource person will be asked to explain about the various faults in single phase Induction
Motor & its trouble shooting methods.
Student Portfolio Additions:
Students can be asked to collect some of the Capacitors/Condensers from an old or
faulty ceiling or table fan & should be able to identify the ratings mentioned & need to
record it.
Video Suggestions:
https://youtu.be/SK5iJArToWA
Answer Key:
It depends on the specification of the Single Phase Induction Motor that has been
used in the Practical Experiment.