AC or
Alternating Current
This type of electron current flows in a wire or electric circuit
in a power supply in such
a manner that it
flows in one direction down a wire and then it reverses and
flows the opposite direction down the wire. The electron
current flow alternates back and forth inside the wire,
first flowing in one direction and then reverses and goes in the
opposite direction. Alternating Current (AC) moves in one direction at the speed of light (almost) down the wire
and after a predetermined amount of time it reverses its
direction; traveling in the opposite direction for and equal
amount of time at the speed of light. The current continues to flip and flop
back and forth alternating (reversing direction) for equal
amounts of time in both directions. This type of
power,
alternating current, is
used by power plants in America for normal power distribution
throughout the country.
The power plant uses rotating generators (Alternators); which alternates the power
direction 60 times a second (aka 60Hz).
Shipboard and Aircraft power generators generally alternate the
power at 400Hz and many foreign countries alternate their power
at 50Hz. AC power is carried or transmitted on two wires known
as the Line and the Neutral. In a modern day properly
wired home, office, or facility the Neutral line is connected to
the Earth Ground to make the Neutral Wire at zero voltage
potential so that it has a "Neutral" electrical charge on it
for personal safety from electric shock.
AC-DC Power Supply
All electronic devices require direct current for proper
operation.
The power mains coming from the power company into the home,
office, work facility, or factory is in the form of Alternating
Current. Therefore some sort of converter must be
used to change the AC Primary Mains into DC Secondary Power.
This type of converter is an AC-DC Power
Supply. Aegis Power Systems manufactures
AC-DC Power Supplies; which convert this AC main primary power
into DC secondary power for use by the customer's electronic
devices. Often times an AC-DC power supply is also known as a DC
Power Supply, Power Converter, or just as a Power Supply.
Agency Approval
Many "Agencies", testing labs, or government regulations are
available that a manufacture can have their electronic products
independently tested to as proof that their product will meet
certain "Safety" compliances as added assurance to the user that
the product will not somehow harm them during use of the
product. Approval is generally done to commercial products
for home and office use. Underwriters Laboratory (UL) is
perhaps the most recognizable testing facility. Not having the "approval" of an
agency does not mean the product is not safe or quality made. It means
that the manufacturer did not see the relevance in spending
large amounts of time, effort, and money for test lab sanctioning on a
product with a limited non-commercial user base that would dramatically
increase the cost of the product to the purchaser.
Ambient
Temperature
Temperature of the non moving air within several inches of the
power supply is referred to as the Ambient. Ambient temperature is often
considered to be
approximately 72ºF or the Temperature of an average Room.
Concerning power supplies, the temperature near and immediately
around the
power supply while performing its normal operation is considered
Ambient. This temperature may be greater than the average
room temperature where the power supply is physically located
due to the heat that is generated inside the power supply.
Ambient Temperature is commonly used as a standard for comparing
power supplies for various specifications, especially cooling or
output power ratings.
American Wire Gauge
A standard since 1857 used for electric wire sizes. It
standardizes the physical diameter of the wire and how much
current it can carry based on the type of metal and type of
insulation that is used in its fabrication.
Amperage
The amount of electrical current flowing in a circuit is
measured in amperes (Amps). This can be thought of
as a physical quantity of electricity which is traveling through
a wire in one second. This is similar in nature and can be
compared to the
amount of water flowing through a hose rated as gallons per
minute. Power supplies are rated as to how much amperage
they will draw from the primary power source and rated as to how
much amperage the power supply can provide to a DC electronic
device connected to its output (load).
AWG - See American Wire
Gauge
Base Plate
The electrical components and hardware pieces of the power
supply must be attached to some sort of frame or "Base" to keep it all
together. The base plate serves this purpose. The
base plate is the foundation or chassis of the power supply
of which all other pieces ultimately connect to. Sort of like
the foundation of a house or the frame of a car.
Black Out
A total loss of power to the power supply input. Generally
the main power source of the facility has gone "Off Line"; or a
primary power fuse blown, or a circuit breaker or contactor of the circuit
providing power to the supply power has tripped or opened
circuit.
Brown Out
A reduction in power, namely a reduced voltage level of the
incoming primary mains power to the power supply. This is
generally caused by the power of the local power company grid not being
sufficient enough to provide power to all of the users connected
to the grid. The grid protects itself by reducing voltage
to keep the current flow at a low level to prevent wiring,
transformers, and other components from being damaged during an
abnormal high current condition.
Burn-In
A method of testing newly manufactured power supplies to force failures to occur at the factory
under supervised conditions before being shipped to the customer.
Generally the power supply is operated at 50-100% of its load capacity
at an elevated ambient temperature to stress the components of
the power supply. Theoretically, any weak components would
fail during this "Burn In" time so that they can be
replaced, thus preventing a premature failure, infant mortality
failure, or other latent defect later in the
customer's system. Aegis Power Systems performs a burn in
period on all of its products before they are shipped.
Convection Cooling
Because power supplies are not 100% efficient when converting
the AC input power to DC output power, they create heat
as a wasteful byproduct. This heat must be removed from the power supply
to keep it from overheating and causing internal damage. One method
of removing heat from the power supply is
convection; which is the natural upward flow of hot air from
a hot surface to a cooler area in the air above. We've all heard that
"Hot air rises", that's convection. Some Aegis products
use this type of cooling
and some products improve the effective cooling by adding fans to force cooler air across the
power supply increasing the natural convection cooling.
Converter Power Supply
A type of power supply that receives an Alternating Current (AC)
input voltage and
provides a Direct Current (DC) output voltage. The Aegis 1PH
series VME Power Supply converters convert the 115VAC 60Hz input power to
up to four Direct Current (DC) separate output voltages.
Conductive Cooling
Power supplies are not 100% efficient in converting the input
power to the output power and create heat as a wasteful
byproduct; One method to remove this heat is
conduction; which is the transfer of heat between two
items that are connected together, in particular two pieces of
metal that are touching each other. Nature causes heat to
travel from the hotter metal to the cooler metal thus causing
the hotter metal to cool. Aegis Power Systems uses this
type of cooling in their VME Power Supplies which are screwed
fast to the frame of the customers equipment allowing the VME
Power Supply heat to conduct to the larger metal of the frame.
Current Limiting
Current limiting is used to reduce the amount of current flow into a power
supply to prevent an overload condition of the customer's
primary input source. Too much current flow
could damage the power supply or the customer's equipment or
cause a brown out of the customer's primary power source. Some Aegis
Power Supplies have an "Inrush" current limiter to limit the
amount of current that flows into the power supply during its
startup period to prevent overloading the customers primary
power source.
Custom Power Supply
A power supply built from "Scratch" using specifications
provided by the customer. The design may be based on an earlier Aegis
design but built specifically to a new customer's design
parameters and operating specifications.
Current Share
The ability of a
power supply to be connected in parallel with another power
supply for the purpose of providing greater output current and
available power. Generally the power supplies are the same
or similar models and are required to have the exact same
voltage outputs.
De-rating
A power supply may not perform exactly the same under all
operational situations. De-rating is sometimes required
under certain circumstances. The most common de-rating
occurs with temperature change. The VME model Aegis Power
Supply will not provide as much power output at operating
temperatures of 85ºC as it will when operated at 70ºC; due to
the nature of the solid state components used in the design.
The output power will be 200W less at the elevated temperature
meaning the output power is de-rated approximately 1.3 watts per
degree above 70ºC.
DC or Direct Current
Current flows in wires and electronic circuitry at speeds near the speed
of light. Direct Current never reverses direction; however
it can stop flowing by intervention of a switch or other
disconnection of the flow. DC Power is carried or
transmitted by two wires identified as Positive and Negative
with the Negative sometimes referred to as the "Common" or
"Return" or on occasion the "Ground" if it is actually connected
to the Earth Ground. Because one wire has a positive voltage
level in reference to the other wire, DC has polarity, a "+" and
a "-". Caution is a must in the hookup of Direct Current wiring
and the polarity "must be observed", meaning that the plus
output from the power supply must connect to the plus input of
the equipment it is powering. Connecting the wires in reverse
could cause damage to the power supply or to the equipment it is
powering. Direct current flows in only one direction
through the circuitry. The amount of current and direction
of current is dependent on the voltage value and voltage
polarity of the current source. The higher the voltage
source the greater the current. Current will flow into the
positive terminal of the the power supply without ever reversing
and flow out of the negative terminal of the power supply
without ever reversing, always in the same direction, from
negative terminals and into positive terminals. In a power
supply current is always flowing in a loop with current flowing
into the positive terminal of the power supply, performing is
function in the power supply, and flowing out of the negative
terminal of the power supply. Direct Current is generally created by chemical or solar means
such as batteries or solar cells. Aegis AC Power Supplies
convert the facilities AC primary power source into Direct
Current for operating the customer's electronic circuitry that
requires DC power.
DC-DC Power Supply
This type of power supply converts a Direct Current (DC) input
voltage of one value into a Direct Current output voltage at
another value. This is generally done when the customer
requires a DC voltage to operate his equipment that is a
different level than what is available in his facility. In
an electric vehicle for instance, the vehicle main battery is
330VDC but the vehicle operates on +12VDC. The AEGIS HEV
series power supplies "Convert" the 330VDC to +12VDC.
Efficiency
A percentage of how much power is provided at the output of the
power supply compared to how much it consumes at its input side
is its efficiency.
A power supply with an efficiency of 80% is considered good and
means that 20% of the input power consumed is used by the power
supply to perform its internal functions. This 20% is
given off as heat by the power supply and must be dissipated
into the air or into the mechanical structure that the power
supply is mounted onto. The higher the efficiency the less
power loss and Aegis strives to manufacture power supplies with
very little power loss. A 100% power
efficiency is ideal and physically unattainable but
manufacturers strive to get as close to perfect as possible.
An efficiency over 90% is considered excellent an is obtainable
with the use of newer technologies; however at higher build
costs.
Electro Magnetic Interference
Simply put, Electro Magnetic Interference,
is electrical noise which interrupts, disturbs, or causes
improper operation of an electronic device. These noises can
be caused magnetically, statically, or by radio waves of other
nearby electronic or electrical devices. Aegis Power
Supplies are designed to filter out this unwanted EMI noise to
limits set by the FCC or Military standards.
EMI - See Electro Magnetic
Interference.
Enclosed Frame Power Supply
Power Supplies come in many different packages. The
enclosed frame power supply simply means it has a cover around
it. Enclosing a power supply can be for several reasons;
safety so that nothing or no one can touch the high voltage
components inside; environmental concerns such as water and
dust; to shield the power supply from nearby electrical noise or
EMI; and of course just to make the power supply esthetically
pleasing to the eye. Many Aegis power supplies are
enclosed if the intent is to mount the power supply where it
would not get any protection from being installed inside another
enclosed box, rack, or equipment.
Filter
EMI and other noise can be disruptive to the operation of
electronic equipment, especially if it is created in a power
supply and passed onto the equipment it is powering. To
rid the power supply of these unwanted noise signals, electronic
noise choking devices consisting of magnetic and capacitive
components are used to shunt the noise into the chassis or
ground circuits so that they will not appear on the output or
input voltage wires.
Firmware
In the high tech world we live in there probably is not a single
electronic device that does not have some sort of microchip
operating under control of a computer program. If the
device is not specifically a computer it still may have some
computer control operations occurring such as tuning your car
radio, operating your TV remote, washing machine, or electric
stove in the kitchen. These operations are done with small
micro programs embedded inside micro chips and are referred to
as "Firmware". The name comes from the fact that it is not
totally reprogrammable like a computer is, it is not "Hard
Wired" like old mechanical timers or factory machinery of years
past; firmware is something in between. The mini program
may be changed somewhat when it is first created and the
programming "tweaked" to the particular electronic gadget it is
going into. Once it is tweaked it generally can no longer
be changed, or maybe only a small percentage of the program can
be changed. Hence it is not Software, it is not Hardware,
and has become known as Firmware.
Ground
Ground makes reference to just that, the natural earth outside
with grass, shrubs, and trees growing from it. Earth
ground is considered electrically neutral in that if you touch
it, you will not receive an electrical shock. It's
electrically neutral. In power supplies the case, base
plate, cover, main metal parts of the power supply are
electrically connected to earth ground through proper wiring or
power supply mounting techniques. The outside of the power
supply is "Grounded" to make it electrically neutral to prevent
a user from receiving an electrical shock when touching it.
Heat Sink
Because power supplies are not 100% efficient; they create heat.
Heat can be detrimental to power supplies and all electronics in
general and therefore must be removed from the power supply.
Using a Heat Sink is one method of doing this and is typically a
piece of metal attached to the power supply. The heat sink
will absorb heat from the power supply through the thermal
conductive properties of metal, its a physics thing.
Larger physical heat sinks will absorb greater amounts of
thermal energy from what it is thermally attached to. The
heat sink will then disperse the heat into the air using natural
convection "Hot air rises". Convection cooling can be
increased by exposing a greater amount of physical flat metal to
the air. Therefore; heat sinks are designed with lots of
ribs or fins to create large amounts of exposed metal to the air
in a small space.
Hi-Pot
- See High Potential
Test.
High Potential Test
This safety test is performed on power supplies to demonstrate
their ability to "withstand" abnormally high voltages that might
be applied to its input wires during an abnormal fault condition.
The test is to provide evidence that the abnormally high input voltage
will not conduct to the case or ground system of the
power supply.
High Voltage Supply
Power supplies come in many varieties with a great number of
output voltages available. "High Voltage" is a relative
term with no definite voltage value universally accepted as the
cross over from low voltage to high voltage. However, it
is generally accepted that any voltage that is touched by human
skin under normal conditions is considered "high voltage" if
some physical harm occurs to the person as a result. Some
accept that if a "live' circuit is human touched and the human
perceives a sensation, then that is high voltage.
Aegis Power Systems will place "High Voltage Warning
Stickers" on any electric circuits that is felt to be a
personal safety issue.
High Voltage Withstand Test
- See High Potential Test
Hold Up Time
This is the amount of time that the power supply will continue
to provide its output power to the load after the input power has been
removed (Unit turned off). This is especially important
for modern electronics such as computers or devices with
microchips as these must preserve and save data of its current
condition before it quits functioning. This is so that when the input power
is restored, the device can continue to operate where it left off.
This "Hold Up" time is generally in milli-seconds (mS) or millionths of a
second. Luckily, modern micro chips are very fast and
therefore do not require a lot of time to perform their "power off"
instructions.
Hot Swappable
Redundancy is important in some power supply applications in
that power supplies are connected in parallel to each other. The
idea is that if one card or module fails, the others in the
system can still carry the load. Often times the power is
critical to the customer's operation and can not be powered down
for replacement of a failed card or module. The system
must be able to operate properly and stay "on line" while the
failed card is extracted and a working replacement card is
inserted in its place. This is know as being "Hot
Swappable", changing power cards during a normal power up
operating condition.
Impedance
All wiring, electric circuits, electronic components are not
perfect. One of these imperfections is that they try to
impede (slow down or stop) the flow of electrical current
through them. This impedance will cause heat to develop as
the electric current passes through the wire. This is especially true of the household
extension cord; which has probably caused more home fires than
any other single reason due to their impedance causing overheating
when large amounts of current flow through them such as in a
portable electric space heater.
Inrush Current
When a power supply is first powered up it consumes a tremendous
amount of power or current flow to get started during the first
moments (less than half a second) of power up. At the
exact moment of power on there is a maximum amount of current
flow (peak flow) that occurs and then instantly starts to slowly
taper down until the normal amount of current flow exists for
the normal operation of the power supply. This abundant
initial startup flow of current is known as the inrush.
Inrush Limiter
- Also see Inrush Current
An electronic circuitry that will limit the amount of current
the power supply draws from the primary input source during
startup. This is also known as a "Soft Start".
Isolated Output
Unless otherwise specified Aegis power supplies are manufactured
so that the output wires are not connected in anyway or through
any direct wiring path to the input wires, ground circuitry or metal cover or
base plate as a safety feature. The output terminals are
"Isolated" or electrically disconnected with no path
to the ground or input circuitry.
Leakage Current
In a perfect power supply or perfect electronic or electric
circuit the electric current will stay inside the wire paths or
circuitry as designed. However, just like your house and
air conditioning, some of that nice cold air will find a way to
leak to the outside. How well the house is built will
determine how much air leaks. The power supply is the same
way, electricity seems to have a way to find sneak paths
allowing very small amounts of current to flow to places that it
was not designed to go. Some current will sneak through
the electronic components, some through insulators, some through
dust or dampness, and some thru the air. A good design
will keep leakage currents to a very tolerable minimum.
Aegis AC-DC power supplies are tested for leakage current to the
case, cover, or frame of the power supply to ensure that the
leakage amount of current is not harmful to the user when the
metal parts are touched.
Liquid Cooling
One of the several methods that Aegis Power Systems uses to keep
the power supply cool is by having liquid channels built into
the base plate allowing cooling liquid to circulate thru and
absorb the power supply heat. This is very effective for the HEV
and MEV series power supplies for use in vehicles that have a
liquid cooling system.
Linear Power Supply
Power supplies can basically be cut in two halves, the primary
input side and the secondary output side.
Power supply designs come in two basic types to create the two
halves; Switch-mode and
Linear. The major difference between the two power
supplies is that the Linear Power Supply uses a standard power
transformer to split the power supply in half and the
Switch-mode Power Supply uses a specialty transformer to split
the power supply in half.
Linear Power Supply:
First the AC power comes into the power supply and
goes through the transformer making the Primary/Secondary split
having AC power on both the Primary and Secondary side:
Secondly the secondary side
rectifies the AC into DC power; Thirdly
the DC power is sampled and a power transistor is used to
regulate the output power.
Switch-mode Power Supply:
First the AC power comes in and is immediately
rectified into DC power; Secondly
the DC is routed to a power FET switch and specialty transformer
making the Primary/Secondary split having DC power on the
Primary side and creating pulsating DC power on the secondary
side; Thirdly the pulsating
DC power is rectified back to pure constant DC power level for
output to the load; Fourthly
the DC output is sampled and fed back to the power FET in the
primary side to adjust the width of the DC pulses to regulate
the output voltage. A technique known as pulse width
modulation that allows greater output power as the width of the
pulsating power pulse increases and less power as the pulse
width decreases. This method allows the output power to
adjust up or down with load changes by varying the width of the
power pulse created by the power FET.
Line Regulation
The power supply output voltage should remain at a constant
value under all of its operating conditions.
Line Regulation is how well the
power supply does this during operations where the input voltage to
the power supply varies with changing conditions at the
facility's
power source. This is expressed as a percentage with 0%
being ideally perfect and never attainable, meaning that the
output would never have a voltage change under all input
conditions. Regulation of 10% would be considered good and
5% as excellent. Sometimes manufacturers give the
regulation as how many milli-volts (mV) the output changes within
a varying input voltage range. For example, if the 115VAC
input is maintained between 105VAC and 125VAC, the 12VDC output
will not change more than 50mV; this computes to (0.5 ÷ 12) as 4.1% regulation.
Load Regulation
The power supply output voltage should remain at a constant
value under all of its operating conditions.
Load Regulation is how well the
power supply does this during operations of varying loads and
varying power requirements of the customer's load. This
is expressed as a percentage with 0% being ideally perfect and
never attainable, meaning that the output would never have a voltage
change under all load conditions. Regulation of 10% would
be considered good and 5% as excellent. Sometimes
manufacturers give the regulation in how many milli-volts (mV)
the output changes within a range of load current output; which can be converted to a
percentage by dividing the mV change by the nominal constant
specified output voltage. For example, suppose the power
supply can supply 0 to 50 amps of current to the customer's load
and the output voltage is specified at +12V and not to change
anymore than 0.5V during the entire range of 0-50A. This computes to (0.5 ÷ 12) as 4.1% regulation.
Mean Time Between Failure
Mean Time Between Failures is a
relative measurement of power supply reliability based on
previous operating data or calculations based on a standard such
as military standard Mil-HDBK-217. MTBF is time expressed
in hours and does not mean the time until the product reaches
its end of life, but rather the amount of time the product is
expected to operate
without a failure. MTBF is a prediction as to how often a
failure might occur according to the law of averages.
Mil-Cots or Military Commercial off the
Shelf
This type of power supply is built by Aegis Power Systems with
Military use in mind when they are designed and manufactured.
They are typically industrial strength products that have been
"beefed" up in some areas to make them more "Robust". They
are meant for general commercial and industrial use and are
normally standard manufactured products for a wide range of
customers and not specifically "Custom" built for the military
or any one customer. The attractiveness to Aegis Cots
products are that they are less costlier to purchase and
available within a much shorter time than designing and
manufacturing a "Custom" made supply.
Military Specification or Mil Spec
Power Supply
A power supply that is specifically built for military use.
It may be designed to one or more military specifications but
not to all military specifications. Aegis power supplies
as noted are built to pass Mil-Std-461 EMI specifications,
and/or portions of the Mil-Std-810 Environmental specifications,
and/or the Mil-Std-1399, Mil-Std-702, and/or Mil-Std-1275 input
power specifications. Exact specifications are discussed
and contracted for during the purchasing endeavor.
MTBF
- See Mean Time Between
Failure
N+1 Redundancy
A power system with N+1 Redundancy has power supply modules
or cards connected in parallel to each sharing the load current. One more supply
than is required is placed in the system, so should one unit fail
the others can safety provide full power to the load. The
failed unit can be removed and replaced while the system is in
operation. For example, in a 1000W system, three 500W modules
might be
installed. Normal Operation requires 2 modules (N), the fault
safe mode requires and additional module (+1) for a total of
three modules. N+1 (Normal +1 Additional).
Noise, Electrical Noise
-
Also see EMI.
Electrical unwanted noise can disturb or cause improper
operation of electronic circuits and have the potential to cause
failures. There are many sources of noise within and
outside the power supply. Inside the power supply can be
thermal agitation of the electronic components, high speed
switching on and off of electronic components, electro-magnetic,
and electro-static interference and interaction between wires
and circuit board paths. Outside the power supply there is
an unlimited source of noise disturbances that could interfere
with the power supplies operation such as radio frequency
interference from communication stations and devices,
automobiles, nearby computers, computer monitors, electric
lightening, electric machinery, etc. Filters are placed
into the power supply to eliminate or reduce these noise levels
to an acceptable value that will not cause interference to the
operation of the power supply.
OEM
-
See Original
Equipment Manufacturer
Open Frame
This type of power supply has no cover or protective case around
it. It is open. It must be installed into the
customer's rack, box, equipment, etc to be protected from the
elements and provide safety to users.
Operating Range
Power Supplies are limited to their abilities to produce an
output by the operating parameters such as power supply input
voltage value, temperature, and humidity conditions that the
power supply is operating under.
Original
Equipment Manufacturer
Some products manufactured by Aegis Power Systems become OEM
products, meaning that our customer purchases them, put their
own name and/or part number on our product and resell them, or
package them into a larger system becoming part of a larger
product being sold by the customer.
Package
This term refers to the physical construction of the power
supply especially concerning how it mounts or is installed to
the customer's equipment. Aegis Power Systems produces its
power supplies in several different packages including ones that
can mount in a standard 19" instrument rack for military,
telecom, or industrial systems; slide in power cards that allow
the power supply to be slid into the customer's existing rack
mounted card rack; completely enclosed cases with mounting holes
or brackets for attachment to the floor, inside wall or outside
wall of the customer's equipment rack, vehicle, cabinet, or
machinery; and open framed construction having no protective
covering for installation inside
the customer's equipment relying on that equipment to
shield and protect the power supply.
Power Converter
This is a power supply that uses components called rectifiers
that transform or convert Alternating
Current Power (AC) into Direct Current Power (DC).
Power Factor
In simple terms, power factor is a number between 0 and 1 that
tells how much power loss exists in a system due to magnetic
devices. "Zero" would indicate the worst case where all
the power is lost and "One" would be the best case scenario when
no power is lost. So a power factor of 0.7 indicates that
70% of the power is transferred through the circuitry and 30% of
the power would be lost. Ideally you would want no power
loss from the magnetic devices and power factor correction
methods can be designed into the power supply to help counter
the power factor losses.
Power Inverter
This type power supply is the inverse of the converter. An
Inverter transforms Direct Current Power into Alternating
Current Power.
Power Supply
A power supply is an electronic device that converts one type of
electrical power into another type of electrical power.
All electronic devices require a power supply. Cell phones
are an example where its
batteries must be recharged by using a small power pack power
supply that plugs into the household electrical wall outlet.
This simple small power supply converts the 115VAC Power of the
wall outlet into a low voltage DC power that will charge the
battery inside the cell phone.
Power Surge
As a rule the power from the power company is fairly steady and
electrically noiseless (Clean). However, on occasions, large
loads may change on the power grid such as a major substation
going on or off line, a possible lightening strike, power line
down and touching the ground, or other
anomaly. During these conditions the power line voltage
can instantaneously spike to a very high abnormal voltage, cause
several of these spikes to occur in a row, or cause an over
current condition to occur. These conditions may only last
for micro or milliseconds and are referred to as power surges, power
spikes, or power transients.
Primary Mains
The main power coming into the power supply. This would be
power from the customer's facility, normally coming from a
breaker or fuse box or possibly directly from a generator in the
case of some military and industrial applications.
Rack Mounted
A type of power supply constructed with an encased housing that
has
mounting brackets on each side of it for mounting into a standard 19"
equipment rack at the customer's site.
Rectifier
Rectifiers are the actual electronic components in a power
supply that convert
Alternating Current (AC Power) into Direct Current (DC Power).
All AC-DC power supplies have rectifiers inside them to do the
main chore of AC to DC power conversion.
Regulation
- see Regulated
Power Supply
Regulated Power Supply
Electronic circuits require a steady level Direct Current
Voltage (VDC)
to operate them. Must circuitry can tolerate small amounts
of deviation but the voltage value (level) must remain fairly
constant overall. The ability of the power supply to keep the
output voltage steady or at a constant value is called
regulation and a power supply that is designed to perform this
is obviously known as a Regulated Power Supply as opposed to the
less expensive unregulated power supply; one which cannot
maintain a steady output voltage level.
Remote Sensing
The power supply keeps its output voltage to a constant
level under all conditions of the changing load (Regulation). To accurately
do this, the power supply must sample or "sense" what the voltage
level is at the input to the customer's equipment. Two wires are connected between the power
supply and the equipment it is providing power to. One wire samples
the positive voltage output line and the other wire samples the
negative line (aka return or common) at the customer's equipment.
This method of sampling the voltage level at the customer's
equipment is known as "Remote Sensing". The power supply
will increase or reduce its output voltage based on the sample
of sensed voltage at the customer's equipment to maintain the voltage at the customer's
equipment at the steady specified value.
Reverse Voltage Protection
When a power supply with a DC output or DC input is connected
up, "Polarity must be Observed." This means that the
positive input terminals of the power supply must be connected
to the positive terminals or wires of the primary input source.
Also, the
positive output terminals or wires of the power supply must be
connected to the customer equipment positive power terminal. If a negative circuit is connected to a positive
circuit damage of equipment may occur, or at the least, there will
be a fault condition and something is not going to properly
function. To protect the power supply from possible damage
due to incorrectly attached input wires a protection circuit is
installed into the power supply that would prohibit it from
powering up.
Ripple Voltage
The voltage output of the power supply should be at a constant
voltage value with
no variations. The internal design of the power supply, in
doing what is necessary to create an output, actually creates
minor variations in voltages internal to itself at various time
intervals. These will appear as high speed cyclic voltage variation
occurrences at the output terminals of the power supply. These occurrences at various high speed or
frequencies can become mixed in with the output voltage and
cause disturbances to the customer's equipment, and
therefore must
be filtered out. The varying voltage frequencies that are not
completely filtered out are know as the
Ripple Voltage or more commonly as
Electrical Noise.
Power Supply output Ripple Voltage is generally measured in milli-volts
(mV) and sometimes as a percentage of output. In linear
power supplies the ripple voltage noise is typically at a 60Hz
frequency as this is generally noise that originated from the
input alternating current of the primary mains (60Hz).
Ripple noise in switching power supplies is typically in the
range of 300Khz to 1Mhz as a result of how fast the internal
components of the power supply operate to convert the AC input
to the DC output. See Aegis Power Systems Tech notes on how Switching Power
Supplies operate.
Schematic
A schematic is the electrical diagram using electronic symbols that show the internal
connection of electronic components in the power supply.
Soft Start
- See Inrush Limiter
Surge
- See Power Surge
Surge Suppression/Suppressor
Suppressors are Electronic Components installed into the power supply to protect
the power supply from Primary Power Line Surges, Spikes, and
Transients. These devices are made so that they will
activate when an input power anomaly occurs and causes the
anomaly to bypass or be shunted around the power supply so that
the power supply will not be harmed.
Switching Power Supply
- See Linear Power Supply
Switch Mode Power Supply
- See Linear Power Supply
SMPS
- Switched Mode Power Supply, See
Linear Power Supply
Thermal
Protection
High temperatures in a power supply or any electronic circuitry
can be detrimental to the electronic components inside and cause improper operation
of the power supply or possible component
failure. As a safety concern to the power supply, thermal
protection is incorporated into Aegis power supply products that will turn
the power supply output off should a predetermined and
programmed level of high
temperature be reached.
Transient-
see Power Surge
Uninterruptible Power Supply
This type of power supply continuously outputs power to its load when
the primary input power to the power supply has been removed or
lost. This is
accomplished because the power supply has a second or alternate input
power source.
The Uninterruptable Power Supply (UPS) has a primary power input and a backup power input.
The backup power input in most cases
is a battery. Should the primary AC power source be cut off or
be lost for some reason, the secondary battery source would continue to
provide power to the power supply with a smooth transition
from primary to alternate power allowing the power supply to provide a
continuous output without any power loss
or power glitches during the switch over from primary to
secondary power.
UPS
- See Uninterruptible Power Supply
Voltage
This is a measurement of how much electrical pressure is forcing
the electron current flow through the wiring or circuitry of the
power supply. This can be
thought of much the same as the water pressure in a water hose.
The higher the water pressure the greater the water flow.
The higher the electrical voltage pressure the greater the
electrical current flow through the power supply.
Withstand Voltage
- See High Potential Test |
