Card Set Information
state ohms law
what is impedance stated as?
z or resistance
what effects must be known before calculating impedance?
state the formula for calculating power
power is defined as_____
the rate of doing work
describe turns ratio of a transformer
it determines the secondary voltage
like magnetic poles_____each other
what instrument measures integrity of insulation of a winding?
what units are used when measuring integrity of a winding?
if a transformer has 4 to 1 ratio with 480v applied to the primary, what is the secondary voltage?
120v. voltage divided by turns ratio
how is a dry transformer cooled?
why cant water be used for cooling a liquid cooled transformer?
no diaelectric, capacitance and no resistance
how is a battery created?
2 or more cells connected together
describe a series connection
they are all in a line
describe a parallel connection
they are stacked
if four 1.5v cells are connected in series, what is the resulting voltage?
what test instrument is used to test potential difference?
define potential difference.
it is the difference in potential energy per unit of charge between 2 pts
what is the oppostion to current flow called?
describe a solenoid
it works off an electromagnet
can a solenoid be used as a control device?
yes, on/off control
what is the insulating material used in any electrical device called?
name 4 good conductors
copper, aluminum, water, metal
name 4 good insulators
plastic, fiberglass, rubber, silicon
a complete cycle of an ac circuit consists of _____ degrees
what is the U.S. standard measure of rate for elecrical power?
describe the difference between primary and secondary storage cells.
secondary cells can be recharged
what liquid can be put into a battery? why?
elecrolyte, because it is a good conductor
what is the density of a material compared to density of water?
what is the S.G. of water?
what does it mean if a battery has a 10 amp hour rating?
it will draw 10 amps for 1 hour
what determines the capacity of a battery?
the size and the number of plates
should batteries be vented when charging?
what is the elecrolyte in a lead acid battery?
water and sulfuric acid
where is a 4way switch used?
where there is more than 2 switches needed in 1 location for controlling 1 light
what does the simplist type of capacitor use for its diaelectric?
air type or paper type
what should be done to a capacitor removed from a circuit?
it should be shorted and discharged
what is the symbol for inductive reactance?
all the power in a circuit is consumed by the wiring...
how many degrees are windings of a 3 phase motor separated?
what metal is usually used to construct small transformer coils?
if an iron core is inserted into a copper core, the magnetic field is increased
a transformer has 4000 turns in the primary coil, and 400 turns in the secondary. what is the secondary voltage if 120 volts is applied to the primary?
12v. voltage of primary times turns of secondary divided by turns of primary
_____voltage is required to run a synchronous motor.
AC and DC
the rotor winding of a large synchronous motor is energized with ____voltage.
how is speed of 3 phase induction motor varied?
by the number of poles or VFD
name the parts of a diode.
anode and cathode
what is the test that measures relationship in ohms of each winding of a 3 phase motor to each other?
what is a bridge rectifier used for?
converting AC to DC
how does an elecrical relay work?
it consists of a magnet armature mounted over an elecromagnet that receives voltage to change position of contacts
what are fuses for?
to protect the wire
what does AWG represent?
american wire gauge
when is arching more prevalent, starting or stopping a motor?
what is another name for a melting alloy overload?
eutectic melting alloy
why is control circuit voltage usually lower than power circuit?
you dont want high voltage close to pushbuttons
how are locations of elements of a schematic referenced to other diagrams?
they are under the element on a schematic
what does TEFC on a motor tag mean?
Totally Enclosed Fan Cooled
what motors are used in a class I division II area?
how are AC ammeters connected?
in series with the load
how are voltmeters connected?
in parallel with the load
what determines wire size?
the current used
which ranges of pressure are manometers commonly used to measure?
low pressures, psi and inches of water
which conditions will damage a pressure element?
pressure transducers receive information in terms of pressure and convert that information to?
electrical signal, or ma
fluid flowing through a pipe exerts pressure in which direction?
as velocity of fluid in a pipe increases, what does the pressure on the pipe wall do?
the quantity of fluid passing a given point in a specific period of time is the expression of?
a hollow tube that can be installed in a pipe with one end open to incoming flow and the other measuring the pressure of flow is ?
what can be determined when the area of a fluid and the velocity are known?
rate of flow
which output signals are associated with electronic control systems?
voltage and current
what signal is generated when the junction of two dissimilar metals are heated?
what will happen to the resistance of a sensing element if the temperature of an RTD is increased?
it will increase
what is commonly used in fluid temp thermometers and why?
mercury. it expands and contracts at a constant rate
which section of a typical positioner automatically determines the position of an actuator?
what must all control loops have?
inputs and outputs
what control functions are used to determine if certain operating conditions are met?
what are the series of mathmatical steps that a controller is programmed to follow?
what is the device that continually compares the value of process variable to the set point?
the tubing of the high side of a transmitter for flow measuring should face?
the upstream of the orifice
which control mode is used alone or in combination with other modes?
in a cascade control system, what does the primary controller do?
set the set point for the secondary or slave controller
what are some parts of a photo electric control system?
emitter, receiver, and reflector
what would the reading be on a delta P instrument with condensed vapor on the low side?
low zero or below zero
a binary number of 0000111 is equal to?
what is the midpoint range for a pneumatic system?
according to ohms law, if the voltage across a resistor is doubled, what happens to the current?
it too is doubled
the best way to check accuracy of a temp thermocouple is with ______
a temperature bath
what is optional in a single variable control loop?
how can parallax error be reduced?
with a mirror
which signal might a digital device receive if a switch closes?
1 or closed
accuracy requirementss for measurement differ according to the _____
which element would you use for the lowest pressure and vacuum measurement?
an advantage of the RTD over the thermistor is ______
the RTD's higher temperature
air supply for a pneumatic transmitter is typically_____
a single data highway uses two cables to provide _____
libraries of _____ are provided for common control functions like PID
a reset of 5 repeats per minute is equal to an integral time of______
12 seconds per repeat
which part of the liquid filled capillary system is usually the only part exposed to the process?
list examples of control elements...
valves, motors, relays, solenoids
what is the most important consideration in a loop control?
dynamics of process
a disturbance within a control loop is corrected by _____
flashing and cavitation in valves often result in _____
where are PLC's best used?
where quick response is needed
all automatic controllers compare _______
process variables to set point
an inductive proximity sensor can be used to detect _____
a logic AND circuit can be represented by 2 or more sets of ___ contacts in series
the temperature range of a thermocouple depends on the _____
the interface device that connects a computer to a network is known as a _____
a major advantage of digital over analog data trasmission is _____
less noise and faster transmission
what is the most important part of hardware documentation for a troubleshooter?
what is one of the main disadvantages of pneumatic control?
if transmitter_____is known, _____ can be calculated
input variable ; output
gain is the inverse formula of _____
how many values can a 3 bit binary number represent?
the accuracy of conversion from sensor output to useful PV data depends largely on ______
the linearity of the sensor
what does proportional action ask?
how big is the error
what is parallax error?
it occurs when reading a gauge at an angle
thermocouple positive wire is usually_____
a typical ouput of a strain gauge bridge circuit is_____
10 to 100 mv
what is the phase to phase voltage of a delta system?
what is the phase to phase voltage of a wye system?
it is 2 times the neutral voltage
how are switches defined and categorized?
by the number of poles and throws
ladder diagrams are known as elementary diagrams
how are contacts of a drum switch manipulated?
rotation of the switch
drum switches are capable of handling currents larger than normal pilot devices
what are limit switches composed of?
actuator and contacts
what are the 2 most common types of proximity switches?
inductive and capacitive
what are 2 types of starter motors?
manual and magnetic
the first thing to do when troubleshooting relays is_____
check for voltage
why are overload relays used?
to protect the motor
how are seal in contacts placed relative to start button contacts?
what configuration do push buttons usually come in?
normally open and normally closed
which starter is operated by a coil inside the contactor?
what are AC motors primarily composed of?
stator, rotor, and end plates
what are the 3 basic parts of a DC motor?
frame, end plates and armature
what determines the speed of an AC induction motor?
the # of poles... more poles make less speed and more power. less poles make more speed and less power.
what are the 2 windings of a single phase motor?
run and start
if poles are removed from an AC motor, speed and horsepower will NOT increase
how do you change rotation on a 3 phase motor?
swapping 2 leads or using a drum switch
what would happen to a single phase AC motor if run winding and start winding were left energized?
they would burn up
what is the opposition of electron flow in a DC circuit?
what is an AC wave form called?