Midterm Controls Flashcards
To reverse the rotation of a single phase motor, you must:
Interchange start winding (or run winding, but not both)
When a motor is being inched its connected to:
A reduced voltage
When a motor is being jogged, it’s connected to:
Full line voltage
A type of device used to detect flow within a pipe
Flow switch
A type of device used to monitor flow rate within a pipe
Flow sensor
A motor starter that provides overcurrent protection, overload protection, and a disconnecting means is called a:
Combination starter
2 basic types of overload relays are:
Thermal and magnetic
A float switch that is used to control a motor directly must be rated to carry:
FLA
When Installing/replacing plug-in relays, the electrician should pay close attention to:
The relays coil voltage
A method of preventing the coils of a reversing starter from energizing simultaneously is known as:
Interlocking
What are the two main parts of a solenoid:
Coil and plunger
Multiple stop buttons used to control a magnetic motor starter are placed in:
Series
Multiple start buttons used to control a magnetic motor starter are placed in:
Parallel
Two wire control provides:
Low voltage release
Three wire control provides:
Low voltage protection
The contacts of a motor starter that carry the FLA of the motor are called:
Pole or Line or Load contacts
A Thermopile exists when:
Two or more thermocouples are connected in series
Copper is used to provide good Thermal contact in what device?
RTD Probe
A device that works on the change of resistance with a change in heat:
RTD - resistance temperature detector
Thermistors exhibit:
Rapid change of resistance with a change in temp
Which relay is a length of resistive wire connected in series with the motor to sense motor current?
Hot wire relay
A device that employs the heating of two dissimilar metals is called a:
Thermocouple
With a spiral bi-metal strip, if a calibrated scale is placed behind the pointer attached to the centre of the spiral, it becomes a:
Thermometer
Two dissimilar metals bonded together have:
Different expansion rates
What type of wire is an RTD is made of:
Platinum wire
The most common heat sensing device used in room Thermostats is:
Bi-metal strip
A long bi-metal strip is desirable because it:
Exhibits a greater movement with change in heat
Which proximity dectectors do not depend on metal to operate?
Capacitive Prox. Detectors
T or F, proximity detectors are basically just metal detectors
True
T or F, Sensors should be mounted as close to other metals as possible?
False
Most ultrasonic detectors have a wide range of adjustable:
Sensing distance
Ultrasonic detectors admit a:
High frequency sound
Most capacitive proximity detectors have a range of approximately:
25mm
A proximity detector that can detect non-metallic objects usually operates on a change in:
Capacitance
With proximity detectors, sensors should be mounted:
As far away from each other as possible
With an all-metal detector, a ferrous metal can be sensed at:
3 times the distance of a non-ferrous metal
All metal detectors operate at:
Radio Frequencies
Proximity detectors are basically:
Metal detectors
Photodetectors that have both the transmitter and the receiver units mounted in the same housing, depend on a ______ for operation.
Reflector
Photodetective devices emit _____ when in the presence of light.
Electrons
T or F, when the CAD cell is in the presence of light, it’s resistance is high.
False
T or F, Photodetectors can be used to sense the presence or absence of almost any object.
True
What are the 3 categories of photo-operated devices:
- Photo-voltaic
- Photo-emissive
- Photo-conductive
The life span of a photodectectors operation is:
Millions of times without damage or wear
To allow or stop current to flow, a photoconductive device changes its…
Resistance with light
Photodectectors detect:
Light
The greatest advantage of a photo-emissive device over other photo dectectors is its:
High speed switching
A photo-emissive device emits:
Electrons when in the presence of light
If neither side of a control transformer is grounded, this is generally referred to as a _____ system
Floating
The 120v secondary control transformer is usually bonded to ground with terminal ______.
X2
What terminal type do control transformers have connected to the primary and secondary leads.
Screw terminals
Magnetic control systems often operate on what voltage?
120V
Most industrial motors operate on voltages that range from:
208V - 600V
When do Omron eleven pin timers change state?
When the preset time has elapsed
Off-delay pneumatic timer contacts change state on:
Energization of the coil
Typically, 8-pin electronic timers are:
On-delay
Timers that operate by restricting the flow of air through an orifice to rubber bellows or diaphragm are:
Pneumatic
Programmable controllers contain _________ electronic timers.
Internal
Periodically, how do pulse timers operate
Continually turn on and off at regular intervals
What determines the full range of time for a clock timer
Gear ratio
T or F, pneumatic timers are limited to either normally open or normally closed contacts
False
A N.O.T.C contact must be connected to an _______ relay when it is to be time delayed when closing.
On-delay
In solenoid valves, digital means that the valve has only ______ states of operation
Two
T or F, Two-way solenoid valves may be normally open or normally closed
True
4 way solenoid valves are generally used to control air supply to:
Double acting cylinders
Two way solenoids usually are used to control the flow of:
Liquids or Gases
If the outlet side of a two-way solenoid valve is connected to the pressure lines, this could cause the valve to:
Leak, not function properly, or not seal properly
