Relay Circuit Assignment - Job #7
Here are the tasks to complete for this assignment. You may want to print
this page. Check off each task when done. Then move on to the next task.
Definitions Before You Begin
Be sure you have an understanding of these terms before beginning this exercise.
You may need to use a dictionary, a code book, a theory book, or even ask other
electricians you may know for help. This is part of the learning activity. Begin
now.
terminology
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definition
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OR operation
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run mode
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jog mode
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inch operation
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n.o. (normally open)
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n.c. (normally closed)
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terminal
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dashpot
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Read this
As background, here are some details which will help you understand this
assignment. If you encounter words, terms, phrases or abbreviations which you do
not understand, then stop. Research the meaning before going on. This is very
important to your learning activity. The essence of any technical education
activity is comprehensive understanding of all topics which are encountered.
Background Information
Click HERE
to go to a PDF document online with all the information about relays you need.
Spend about ten minutes looking over this wonderful source of detail.
SOURCE Read through these
details.
OVERLOAD RELAY.- The overload relay (fig. 5-12) consists of a coil, a
plunger, a dashpot, and a pair
Figure 5-12.-Over1oad relay.
of switch contacts. The plunger is attached to a disk suspended in an
oil-filled chamber (dashpot). The coil connects in series with an associated
440-volt motor supply circuit and the switch contacts are in a 115-volt
start-and-run circuit for the motor.
During normal operation, the magnetic flux induced by the coil is not great
enough to cause an appreciable movement of the plunger. However, if an overload
of sufficient magnitude and duration occurs, the increased current through the
coil draws the plunger upward.
When the plunger and disk reach the end of their upward travel, the normally
closed contacts open in the 115-volt start-and-run circuit, de-energizing the
motor contactor which opens the 440-volt motor supply circuit. With the motor
circuit open, the overload relay plunger drops and the relay resets.
Since the dashpot retards upward movement of the plunger disk, the circuit
does not break instantaneously during an overload. Two conditions determine the
delay time: (1) the size of the orifice in the plunger disk through which the
oil must pass and (2) the magnitude of the overload (strength of the magnetic
field).
Go to the Diagram of this Job
Click HERE to go to the diagram, lecture, and picture for this exercise. Follow
the instructions found there. Then return to this page with your back button.
Connect the Components
Use the material list on the diagrams page to have ready all the components you
will need to complete this exercise. Connect all required components based on
the diagram.
Check your Connections
With the diagram as a guide, verify that all the connections have been made
properly.
Apply Power To Test
Wear safety glasses when testing this circuit. Locate the overcurrent protective
device for the circuit you will use. If possible, connect to a GFCI protected
circuit for the added safety. Be sure you have a full understanding of this
circuit before applying power. Then when you test the circuit, there should be
no problem with it working properly. Make corrections to the wiring as needed so
the circuit works properly. Memorize these connections.
Sketch the diagram from Memory
A sure way to determine if you have internalized this circuit is to draw a
sketch of the diagram from memory. You may choose to use a straight edge. But
that is not necessary. When you have completed the sketch, check it against the
diagram which is given for accuracy. Electricians must have the ability to
remember circuit connections without reference. Here is your chance to
demonstrate what you have learned. If you are unable to sketch the ladder
diagram from memory, refer back to the given ladder diagram. Then try again.
Repeat this activity until you feel confident that you can sketch this specific
diagram without reference.
Reconnect From Memory
Now on to the real test. Reconnect this diagramed circuit from memory. This will
ultimately tell you if you understand this circuit or not.
Review Before Answering Questions
Go back to review definitions, the diagram, the picture, your notes, your sketch
and any other details which will help you as you move on to the questions about
this diagram.
Answer the Questions
When you are satisfied that you can draw a sketch of the diagram, and wire it
all from memory, it is time to go on to answer questions about the diagram.
Click HERE to go to the questions.
Check Your Answers
When you have completed the questions, go on to check your answers. If you have
any which are different than the given answers, try to determine the reason. Go
back to the diagram. Research the question. Ask other electricians you may know.
But do all it takes to understand the correct answer to each question.
Click HERE to go to the answers.
Go On
When you can answer all questions without error, and strongly feel you
understand all answers, it is time to go on to the next assignment.
Click HERE to go on to the next assignment page.
If you would like to research any of these topics further, enter the search
term in this Google Search Box:
Use these Relay Circuit links to go to where you left off in
your online activities.
Job
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Assignment
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Diagram
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Lecture
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Picture
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Questions
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Answers
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