Chapter 9 Flashcards
The two basic parts of an electromechanical relay are the
______________________ and the _________________ .
coils
comtacts
The two circuits associated with a relay are the:
a. Primary and secondary
b. Control and load
c. Normally open and normally closed
d. High and low
b
Relays are used to control large loads of 15A or more.
(True/Fa1se) ____________
F
An electromechanical relay normally will have only one _________________ ,
but it may have a number of different _____________________ .
coil
contacts
- Normally closed contacts are defined as those contacts that are closed
when the coil is ______________________ .
- State the correct type (N.O. or N.C.) and label for each of the contacts associated with the relay coil of Figure 7-2.
(a) ______________________
(b) ______________________
Figure 7-2
not energized
NO
NC
- Which of the following is not a common application for a relay?
a. To control a 120-V lighting circuit with a 12-V control circuit.
b. To control several switching operations by a single separate current.
c. To change alternating current to direct current.
d. To switch a small servo motor with a low-current sensor signal. - The coil and contacts of a relay are not normally electrically insulated from
each other. (True/Fa1se) ____________
C
F
- Relay options that aid in troubleshooting may include:a. _________________
b. _______________ - It is possible for a relay coil to be rated for 24 V DC and its contacts to be
rated for 240 VAC. (True/Fa1se) ____________
on off indicator
manual overide
- Electromechanical relay contacts may be constructed as
a. N.O. or N.C. contacts.
b. Single-break or double-break contacts.
c. Fixed and movable contacts.
d. All of these
d
a. ______ pole, _______ throw,
______ break
b. ______ pole, _______ throw, ______ break
c. ______ pole, _______ throw, ______ break
d. ______ pole, _______ throw, ______ break
1 2 1
2 2 1
1 2 2
3 2 2
- The load-carrying capacity of contacts is normally given as a current value for a:
a. Resistive load
b. Inductive load
c. Capacitive load
d. Shorted load - A relay contact rates 12A at 12VDC can switch ___________ A at 48VDC.
a
3
- In the symbol of the solid-state relay (SSR) shown in Figure 7-5, the #1 set of leads is comparable to
the _________________________ leads of an electromechanical relay, and the #2 set to the _______________________ leads. - List three common main switching semiconductors used in solid-state relays:
a. __________________
b. ___________________
c. _____________
coil
contacts
Bipolar transistor
mosfet
SCR
- A common method used to provide isolation is to have the input section illuminate which of the following items below, which will activate a photodetective device?
a. LED
b. SCR
c. Transistor
d. Triac - Identify the components of the solid-state relay shown in figure 7-6:
a. ____________________
b. _______________________
c. _______________________
d. ____________________
Figure 7-6
a
LED
phorotransistors
trigger
triac
- The input section of the solid-state relay (SSR) acts like the contacts of an electromagnetic relay (EMR). (True/Fa1se) ____________
- The use of solid-state relays is not recommended for loads that must be switched continually and quickly. (True/Fa1se) ____________
False
Fasle
- Most SSRs have a variable input voltage range. (True/Fa1se) ____________
- A majority of SSRs are multiple-pole devices. (True/Fa1se) ____________
T
F
What type of SSR switching is primarily designed to work with resistive loads?
a. Instant-on switching
b. Peak switching
c. Phase-shift switching
d. Zero switching
d
- ______________________________________ SSR switching initiates the output at the exact same time the input signal is received.
- Zero switching of resistive loads increases the inrush current. (True/Fa1se) ____________
instant on
F
- Compared to electromechanical relays, solid-state relays:
a. Do not exhibit contact bounce
b. Have a much faster response time
c. Do not generate as much electromagnetic interference
d. All of these - Compared to EMR contacts, the SSR switching semiconductor has a much lower on-state resistance. (True/Fa1se) ____________
d
F
- Timing relays are used to _________________________ the opening or closing of contacts for circuit control.
- Contacts of a synchronous clock timer are tripped by
a. Hand
b. An electromagnet
c. Tabs set along a timing wheel
d. A control signal
delay
C
- Synchronous clock timers are not accurate enough for critical timing processes. (True/Fa1se) ____________
- Timing is managed in a dashpot pneumatic timer by controlling _____________________________ flow through a small orifice.
T
fluid or air
- Pneumatic timers have a relatively narrow timing range. (True/Fa1se) ____________
- Compared with dashpot timers, solid-state timers:
a. Provide much more accurate timing
b. Have a narrower timing range
c. Are initiated by an electromagnetic coil
d. All of these
T
a
Draw the symbol for the timer contacts listed below:
Fdsafdsafdsa?#
3
3
3
Examine the timing diagrams of Figure 7-10 and identify the timer type as DOE, DODE, one-shot, or recycle.
fsdafadfdas
- Answer the following with reference to the timer circuit of Figure 7-11:
a. What is the state (open or closed) of contact TR1-1 prior to the switch being closed?
b. What is the state of contact TR1-2 immediately after the switch is closed?
c. What is the state of contact TR1-1 after 5 seconds of the switch being closed?
d. What is the state of contact TRl-2 after 10 seconds of the switch being closed?
e. What is the state of contact TR1-1 as soon as the switch is opened?
Figure 7-11
O C O O O
a. What is the state (open or closed) of contact TR1-2 prior to the switch being closed?
b. What is the state of contact TR1-1 immediately after the switch is closed?
c. What is the state of contact TR1-2 immediately after the switch is opened?
d. What is the state of contact TR1-1 after 10 seconds of the switch being opened?
e. What is the state of contact TR1-2 after 10 seconds of the switch being opened?
Figure 7-12
C C O O C
diagram of Figure 7-13:
a. What are the pin numbers for the normally open contact?
b. What are the pin numbers for the normally closed contact?
c. Identify the pin numbers where the constant voltage source is to be connected:
d. Identify the pin numbers where an external trigger switch is to be connected:
31
41
27
56
Figure 7-14 is set for a time delay period of 5 seconds. For how long would the load be energized for each of the following scenarios (conditions)?
a. The initiate button is held closed for 1 second:
b. The initiate button is held closed for 5 seconds:
c. The initiate button is held closed for 10 seconds:
d. The initiate button is held closed for 2 seconds, but power is lost after 1 second:
5
10
15
1
- Answer the following with reference to the recycle timer shown in Figure 7-15:
a. What type of recycle timer (symmetrical or asymmetrical) is this? Answer ___________
b. How is the on period timing adjustment accomplished?
Answer _____________
c. How is the off period timing adjustment accomplished?
Answer ____________
d. How is the on/off recycling of the contacts stopped?
Answer _________
Asymmeytricall
Step djust knob
Remove input voltage
- The term ________________ timer is reserved for a group of solid-state timers that perform more than one timing function.
- A programmable logic controller can be programmed to implement conventional timer functions. (True/Fa1se) ____________
multifunction
T
- Latching relays use a ______________________ latch or permanent __________ to hold the contacts in their last energized position.
- In a latching relay that uses two coils, the coils are identified as the ____________________ coil and the ____________________ coil.
mechanical
magnet
- Latching relays can provide circuit continuity during power failures. (True/Fa1se) ____________
- In a two-coil latching relay, the latch coil requires what type of a flow of current to set the latch and hold the relay in the latched position?
a. Direct
b. Alternating
c. Continuous
d. Pulsed
T
d
On electrical diagrams, the contacts of a latching relay are normally shown:
a. in their latched position
b. in their unlatched position
c. energized
d. deenergized
b
- Answer the following with reference to the latching relay circuit of
Figure 7-17:
a. How is the pilot light turned on?
Answer \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
b. How is the pilot light turned off?
Answer \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Figure 7-17
t
Assume the unlatch coil is faulted open. How would this affect the operation of the circuit?
Answer ___
t
- Single-coil magnetic latching relays are designed to be polarity sensitive. (True/Fa1se) ____________
- Alternating relays are used to equalize the __________________ of two loads.
T
run time
___________ - ________ alternating relays have the ability to alternate the loads during normal workloads and then operate both when the load is high.
crossed wire
Figure 7-18:
a. What configuration of relay contacts is used?
Answer ____________
b. What initiates the switch in output between Load A (LA) and Load B (LB)?
Answer \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
c. Remote pilot lights are to be connected to the
unused contacts of the relay to indicate which load is active. To which two pins would the pilot lights for load A (LA) and load B (LB) be connected?
Answer _____________
Figure 7-18
DPDT
Open s1
pin 9 and pin 6
Relay control logic and ladder diagrams are the primary programming language for _________________________
PLC
The two separate and distinct parts of a motor control circuit are the primary and secondary sections. (True/Fa1se) ____________
- The input section of a control circuit provides the:
a. Signals
b. Source
c. Actions
d. Load
F
a
of Figure 7-20.
a. List all the component parts that are considered to be inputs:
b. List all the component parts that are considered to be outputs:
c. Which output would be energized with power applied and the circuit in the state shown?
d. Assume that the contactor coil becomes faulted open. In what way would the normal operation of the circuit be affected when the temperature switch closes?
on off, limit switch, flat switch, temp switch, relay contact
relay coil, horn, solo noid, contactor coil, pilot light , heater
solonoid
coil would not close
All input devices can be classified as being loads.
(True/Fa1se) ____________
False
- Logic functions describe how inputs interact with each other to control the
outputs. (True/Fa1se) ____________ - Logic is the ability to make decisions when one or more different factors must be taken into consideration. (True/Fa1se) ____________
True
True
a. Two or more inputs are connected in series and they all must be closed to energize the load. Answer ______________________
b. Two or more inputs are connected in parallel and anyone of the inputs can close to energize the load. Answer ______________________
g
