Industrial Motor Control
7th Edition
ISBN: 9781133691808
Author: Stephen Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 27, Problem 1RQ
Refer to the circuit shown in Figure 27–2. Would it be possible to replace the hand-off-auto switch in this circuit with a hand-off-auto switch that contained a common terminal and center Off position like the HOA switch shown in Figure 27–1? Explain your answer.
Expert Solution & Answer
To determine
Whether it is possible to replace the hand off auto switch in the circuit with the hand off auto switch that contains the common terminal and center off position like the HOA switch shown in the Figure 27-1.
Explanation of Solution
Refer to the Figure 27-1
Consider that the motor is controlled by the hand off automatic switch. In case the position of the contact is at the center off then the motor stops to work.
Refer to the Figure 27-2
Consider both the switch contains the hand off and the automatic switch to control the fan that pulls the air through the building. In that case the switch is same as of Figure 27-1
As both the switch has Hand off and the automatic position the switch contains the two sets of the contacts one is 1-2 and the other is 3-4. In case the set is in hand position then the connection is made in between the contacts terminal 1 and 2 and in case the set is in automatic position the connection is made between the 3-4 terminals and when the set is off no connection is made in between the terminals.
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Section 5-2: Line Diagrams-Signals,
Decisions, and Actions
In the following application, a temperature switch controls a heating contactor and a flow switch is used to
ensure there is enough air flow. If there is not enough air flow, an alarm is sounded. Complete the required
information.
1. List all the signal devices in the circuit.
2. List all the action devices in the circuit.
3. List the decision part of the circuit that automatically sounds the alarm if there is a problem.
4. When the heating element is on during normal operation, is the flow switch open or closed?
CIRCULATING
2
L1
FAN
TEMPERATURE
SWITCH
TR
HEATING
ELEMENTS
FLOW
SWITCH
-HOT AIR
PADDLE
AIR FILTER
NORMALLY CLOSED
FLOW SWITCH
65
ALARM
(SOUNDS IF NO FLOW FOR
15 SECONDS OR MORE)
Date
HEATING
CONTACTOR
TR
ON-DELAY
TIMER
SUPPLY AIR
COLD AIR
(3) TIME SET= 15 SEC
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All rights reserved
Draw a series circuit with a thermostat,a low-pressure switch, and a highpressure switch used as safety controlsto protect a motor
Select the proper choice(s) for each of the following statements:
1) To control single-acting cylinder we just need:
double-acting cylinder we should use
A2/2-way, 5/2-way,
(C) 3/3-way, 3/4-way,
2) In
DCV.
(B) 3/2-way, 4/2-way,
(D) 4/3-way, 3/2-way.
mid poistion of DCV, we can move cylinder piston rod freely without
resistance by hand.
(A) working ports are exhausted,
(C) working ports are pressurized,
3) In pneumatics we use
A Compressor
(B) Pump,
DCV, while to control the
4) Quick exhaust valve is used to
(A) increase the cylinder return speed.
(C) meter-out the cylinder speed
(B) all ports are closed.
no one of these options.
to obtain high pressure air.
(C) Turbine,
(D) pressure relief valve.
(B) meter-in the cylinder speed,
(D) increase the cylinder extending speed.
6) Meter-in of cylinder movement is used to control the
Afluid that enters the hydraulic cylinder,
(B) fluid that exits the hydraulic cylinder,
(C) fluid that enters the DCV
(D) fluid that exits the DCV.
5) One of the…
Chapter 27 Solutions
Industrial Motor Control
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