Design of Three Flashing Lights

Objectives:

• Design a motor control circuit using timers.

• Discuss the operation of this circuit.

• Connect this circuit in the laboratory.

LABORATORY EXERCISE

Name __ Date __________

Materials Required

Materials depend on the design of the circuit The design of this circuit will be somewhat similar to the circuit in Unit 37. This circuit, however, contains three lights that turn on and off in sequence. Use the space provided in Ill. 1 to design this circuit. The requirements of the circuit are as follows:

1. A toggle switch is used to connect power to the circuit. When the power is turned on, light #1 will turn on.

2. After a delay of 1 second, light #1 will turn off and light #2 will turn on.

3. After a delay of 1 second, light #2 will turn off and light #3 will turn on.

4. After a delay of 1 second, light #3 will turn off and light #1 will turn back on.

5. The lights will repeat this action until the toggle switch is opened.

Procedure

1. After the design of your circuit has been approved by your instructor, connect the circuit in the laboratory.

2. Test the circuit for proper operation.

3. Disconnect the circuit and return the components to their proper location.

QUIZ:

1. A 60 hp, three-phase squirrel cage induction motor is to be connected to a 480 volt line.

What size NEMA starter should be used to make this connection?

2. An electrician is given a NEMA size 2 starter to connect a 30 hp, three-phase squirrel cage motor to a 575 volt line. Should this starter be used to operate this motor?

3. Assume that the motor in question 2 has a design code B. What standard size inverse time circuit breaker should be used to connect the motor?

4. The motor described in questions 2 and 3 is to be connected with copper conductors with type THHN insulation. What size conductors should be used? The termination temperature rating isn't known.

5. Assume that the motor in question 2 has a nameplate current rating of 28 amperes and a marked service factor of 1. What size overload heater should be used for this motor?