ILT 115 Relays
The coil and contacts of a relay are not normally electrically insulated from each other
False
A latching relay is sometimes referred to as a memory relay
True
The two circuits associated with a relay are the
control and load
Compare with dashpot timers, solid state timers
provide much more accurate timing
Normally closed contacts are contacts that are closed when the coil is de-energized and open when the coil is energized.
True
The input section of a solid state relay acts like the coil of an electromechanical relay
True
Latching relays use a ___________ catch or permanent ___________ to hold the contacts in their last energized position.
Mechanical; magnet
On electrical diagrams, the contacts of a latching relay are normally shown in the
unlatched position
It is normal to measure a small voltage drop across the normally open output terminals of a solid state relay when the relay is switched on
True
Latching relays can provide circuit continuity during power failures
True
Logic functions describe how inputs interact with each other to control the outputs.
True
Logic is the ability to make decisions when one or more different factors must be taken into consideration
True
Most solid state relays have a variable input voltage range
True
SIngle coil magnetic latching relays are designed to be polarity sensitive
True
Solid state relays do not generate as much electromagnetic interference as electromechanical types
True
Solid state timers use an RC time constant or quartz clock as their time base
True
The timed contacts of a timer relay delay changing their position when the coil is energized or de-energized
True
The two separate and distinct parts of a motor control circuit are the input and output sections
True
The use of solid state relays is recommended for loads that must be switched continually and quickly
True
The current that can be handled by the contacts of a relay is the same that required to operate the coil
False
The drop out voltage of an electromechanical relay is normally higher than the pick up voltage
False
The majority of solid state relays are multiple pole devices
False
When power is first applied to the coil of an OFF- delay timer, the contacts delay changing position for some period of time
False
Zero voltage switching of AC loads increases the in-rush current
False
In a two coil latching relay the latch coil requires a _______ flow of current to set the latch and hold the relay in the latched position
pulsed
Alternating relays are use to equalize the _________________ of two loads.
operating time
An electromechanical relay normally will have only one _______ but it may have a number of different __________.
coil; contacts
The two basic parts of an electromechanical relay are the _______ and the _________.
coil; contacts
Solid state relays use __________________ as switching devices
semiconductors
The input section of a control circuit provides the
signals
It is possible for a relay coil to be rated for 24 VDC and its contacts to be rated for 240 VAC
true
Solid state relays are normally sealed units that cannot be repaired
true
Which of the following is not a common application for a relay
to change alternating current to direct current
A solid state relay designed to control a DC load may use a transistor to connect the load to the line
True
An electromechanical relay will usually have only one coil but may have any number of different contacts.
True
In an optically coupled solid state relay, the output is isolated from the input by means of a light emitting diode (LED)
True
In a latching relay that uses two coils, the coils are identified as the ______ coil and the ________ coil
latching; unlatching
Which of the following is not an advantage of solid state relays over electromechanical relays
less susceptibility to damage from voltage and current spikes
What type of sold state relay switching is primarily designed to work with resistive loads
zero switching
A programmable logic controller cannot be programmed to implement conventional timer functions
False
All input devices to a motor control circuit can be classified as being load devices
False
Compared to EMR contacts, the SSR switching semiconductor has a much less ON state resistance
False
Control relays are used to switch large motor loads.
False
Like electromechanical relays solid state relays have coils ad contacts
False
Pneumatic timers have a relatively high timing range
False
Relay control logic and ladder diagrams are the primary programming language for _________.
PLC's (Programmable lodging controls)
Timing is managed in a dashpot pneumatic timer by controlling ________ flow through a small orifice.
air
An electromechanical relay is basically
an electromagnet used to switch contacts
Timing relays are used to _______ the opening or closing of contacts for circuit control.
delay
A relay can be considered digital in nature because it
is basically an ON/OFF device
For an electromechanical relay, the amount of voltage and current required to energize the relay coil is
more than what is required to de-energize the coil
The load carrying capacity of relay contacts is normally given as a current
resistive load
Contacts of a synchronous clock timer are tripped by
tabs set along a timing wheel
