Samlex America PST-15S-24A User Manual
DC-AC
Inverters
PST-15S-12A
PST-15S-24A
Owner's
Manual
Please read this
manual before
operating your
Inverter
INDEX
INDEX
Safety Instructions ............................................................................................. 2,3
Inverters - General Information ...................................................................... 4,5,6
Characteristics of Sinusoidal AC Power............................................................... 7
Advantages of Sine Wave Inverters ...................................................................... 8
AC Power Distribution and Grounding ..................................................... 9,10,11
Limiting Electromagnetic Interference (EMI) ...................................................... 11
Powering direct/embedded SMPS....................................................................... 12
Principle of Operation ......................................................................................... 13
Layout................................................................................................................. 13
Specifying Batteries, Chargers and Alternators ................................ 14,15,16,17,18
Installation ........................................................................................ 19,20,21,22,23
Operation ........................................................................................................ 24,25
Protection Against Abnormal Conditions ....................................................... 25,26
Troubleshooting Guide ................................................................................... 27,28
Specifications...................................................................................................... 29
Warranty ............................................................................................................. 30
Page 1
SAFETY INSTRUCTIONS
Please read these instructions before installing or operating the inverter to prevent personal
injury or damage to the inverter.
GENERAL
Installation and wiring compliance
- Installation and wiring must comply with the local and national electrical codes and must
be done by a certified electrician
Preventing electrical shock
- Always connect the grounding connection on the inverter to the appropriate grounding
system
- Disassembly / repair should be carried out by qualified personnel only.
- Disconnect all AC and DC side connections before working on any circuits associated with
the inverter. Turning the on/off switch on the inverter to off position may not entirely
remove dangerous voltages
- Be careful when touching bare terminals of capacitors. The capacitors may retain high
lethal voltages even after the power has been removed. Discharge the capacitors before
working on the circuits
Installation environment
- The inverter should be installed indoor only in a well ventilated, cool, dry environment
- Do not expose to moisture, rain, snow or liquids of any type.
- To reduce the risk of overheating and fire, do not obstruct the suction and discharge
openings of the cooling fans
- To ensure proper ventilation, do not install in a low clearance compartment
Preventing fire and explosion hazards
Working with the inverter may produce arcs or sparks. Thus, the inverter should not be used
in areas where there are inflammable materials or gases requiring ignition protected equipment. These areas may include spaces containing gasoline powered machinery , fuel tanks,
battery compartments
Precautions when working with batteries.
- Batteries contain very corrosive diluted sulphuric acid as electrolyte. Precautions should be
taken to prevent contact with skin, eyes or clothing
- Batteries generate hydrogen and oxygen during charging resulting in evolution of explosive
gas mixture. Care should be taken to ventilate the battery area and follow the battery
manufacturer’s recommendations.
- Never smoke or allow a spark or flame near the batteries.
- Use caution to reduce the risk of dropping a metal tool on the battery. It could spark or short
circuit the battery or other electrical parts and could cause an explosion.
- Remove metal items like rings, bracelets and watches when working with batteries. The
batteries can produce a short circuit current high enough to weld a ring or the like to metal
and thus cause a severe burn.
- If you need to remove a battery, always remove the ground terminal from the battery first.
Make sure that all the accessories are off so that you do not cause a spark
Page 2
INVERTER RELA TED
Preventing paralleling of the AC output
The AC output of this inverter cannot be synchronised with another AC source and hence, it
is not suitable for paralleling. The AC output of the inverter should never be connected
directly to an electrical breaker panel / load center which is also fed from the utility power /
generator. Such a connection may result in parallel operation of the different power sources
and AC power from the utility / generator will be fed back into the inverter which will
instantly damage the output section of the inverter and may also pose a fire and safety
hazard. If an electrical breaker panel / load center is fed from an inverter and this panel is also
required to be powered from additional alternate AC sources, the AC power from all the AC
sources like the utility / generator / inverter should first be fed to a manual selector switch
and the output of the selector switch should be connected to the electrical breaker panel /
load center.
T o prevent possibility of paralleling and severe damage to the inverter, never use a simple
jumper cable with a male plug on both ends to connect the AC output of the inverter to a
handy wall receptacle in the home / RV.
Connecting to multi-wire branch circuits
Do not directly connect the hot side of the inverter to the two hot legs of the 120 / 240 VAC
electrical breaker panel / load centre where multi-wire ( common neutral ) branch circuit
wiring method is used for distribution of AC power. This may lead to overloading / overheating of the neutral conductor and is a risk of fire.
A split phase transformer ( isolated or auto-transformer ) of suitable wattage rating ( 25 %
more than the wattage rating of the inverter ) with primary of 120 VAC and secondary of
120 / 240 VAC ( Two 120 VAC split phases 180 degrees apart) should be used. The hot and
neutral of the 120 VAC output of the inverter should be fed to the primary of this transformer and the 2 hot outputs ( 120 VAC split phases ) and the neutral from the secondary of
this transformer should be connected to the electrical breaker panel / load centre.
Preventing input over voltage
It is to be ensured that the input voltage of the inverter does not exceed 16.5 VDC (PST15S-12A) or 33 VDC (PST-15S-24A) to prevent permanent damage to the inverter. Please
observe the following precautions:
- Ensure that the maximum charging voltage of the battery charger / alternator / solar charge
controller is below 16.5 VDC (PST-15S-12A) or 33 VDC (PST-15S-24A)
- Do not use unregulated solar panels to charge a battery. Under cold ambient temperatures,
the output of the solar panel may exceed 18 VDC for 12V battery system of 36VDC for
24V battery system. Always use a charge controller between the solar panel and the
battery.
- Do not connect the inverter to a battery that has a voltage higher than the rated battery
input voltage of the inverter.
Preventing reverse polarity on the input side
When making battery connection on the input side, make sure that the polarity of battery
connection is correct (Ensure that the centre contact of the cigarette lighter receptacle is
connected to the positive of the battery. The centre pin (tip) of the cigarette lighter plug
attached to the inverter is positive). If the input is connected in reverse polarity, DC fuse
inside the inverter will blow and may also cause permanent damage to the inverter.
Page 3
INVERTERS - GENERAL INFORMATION
Why an inverter is needed
The utility grid supplies you with alternating current (AC) electricity. AC is the standard
form of electricity for anything that “plugs in” to the utility power. Direct current (DC)
electricity flows in a single direction. Batteries provide DC electricity. AC alternates its
direction many times per second. AC is used for grid service because it is more practical
for long distance transmission. For more details read “Characteristics of Sinusoidal AC
Power” on page 7.
An inverter converts DC to AC, and also changes the voltage. In other words, it is a
power adapter. It allows a battery-based system to run conventional AC appliances
directly or through conventional home wiring. There are ways to use DC directly, but for
a modern lifestyle, you will need an inverter for the vast majority, if not all of your loads
( in electrical terms, “loads” are devices that use electrical energy).
Incidentally, there is another type of inverter called grid-interactive. It is used to feed
solar (or other renewable) energy into a grid-connected home and to feed excess energy
back into the utility grid. This inverter is NOT grid interactive
Inverter should meet the application
To choose an inverter; you should first define your needs. Where is the inverter to be
used? Inverters are available for use in buildings (including homes), for recreational
vehicles, boats, and portable applications. Will it be connected to the utility grid in some
way? Electrical conventions and safety standards differ for various applications, so don’t
improvise.
Electrical Standards
The DC input voltage must conform to that of the electrical system and battery bank. 12
volts is recommended for small, simple systems. 24 and 48 volts are the common
standards for higher capacities. A higher voltage system carries less current, which makes
the system wiring cheaper and easier.
The inverter’s AC output must conform to the conventional power in the region in order
to run locally available appliances. The standard for AC utility service in North America
is 120 and 240 Volts at a frequency of 60 Hertz (cycles per second). In Europe, South
America, and most other places, it is 230 volts at 50 Hertz.
Power capacity – “Continuous” and “Surge”
How much load can an inverter handle? Its power output is rated in Watts. Read details
under “Characteristics of Sinusoidal AC Power” on page 7. There are two levels of
power rating -a continuous rating and a surge rating. Continuous means the amount of
power the inverter can handle for an indefinite period of hours. When an inverter is rated
at a certain number of Watts, that number generally refers to its continuous rating. The
“surge power” indicates the power to handle instantaneous overload of a few seconds to
provide the higher power required to start certain type of devices and appliances.
Page 4
Loads that require “surge power” to start
Resistive types of loads (like incandescent lamps, toaster, coffee maker, electric range,
iron etc) do not require extra power to start. Their starting power is the same as their
running power.
Some loads like induction motors and high inertia motor driven devices will initially
require a very large starting or “surge” power to start from rest. Once they have started
moving and have attained their rated speed, their power requirement reduces to their
normal running power. The surge may last up to 5 seconds.
TVs and microwave ovens also require surge power for starting. The manufacturers’
specification of the appliances and devices indicates only the running power required.
The surge power required has to be guessed at best. See below under “Sizing of inverter
for loads that require starting surge”
If an inverter cannot efficiently feed the surge power, it may simply shut down instead of
starting the device. If the inverter’s surge capacity is marginal, its output voltage will dip
during the surge. This can cause a dimming of the lights in the house, and will sometimes
crash a computer.
Any weakness in the battery and cabling to the inverter will further limit its ability to start
a motor. A battery bank that is undersized, in poor condition, or has corroded connections,
can be a weak link in the power chain. The inverter cables and the battery interconnect
cables must be sized properly. The spike of DC current through these cables is many
hundreds of amps at the instant of motor starting. Please follow the instructions under
"Installation - DC side connections" on pages 20 & 21.
Sizing of inverter for loads that requir e starting surge
Observe the following guideline to determine the continuous wattage of the inverter for
powering loads that require starting surge. (Multiply the running watts of the device/
appliance by the Surge Factor)
*NOTE: The surge power rating specified for this inverter is valid for duration
of less than 1 second. This very short duration may not be sufficient to
start motor based loads which may require up to 5 seconds to complete
starting process. Hence, for purposes of sizing the inverter, use only the
continuous power rating of this inverter.
Type of Device or Appliance Surge Factor for Determining the Continuous *Wattage of the Inverter
(No. of times the running power rating of the device/appliance)
Refrigerator / Freezer 5
Air Compressors 4
Dishwasher 3
Automatic W asher 3
Sump pump 3
Furnace fans 3
Industrial motors 3
Portable kerosene / diesel fuel heater 2
Circular saw 3
Bench Grinder 3
Page 5
Power rating of Microwaves
The power rating of the microwave generally refers to the cooking power. The electrical
power consumed by the microwave will be approximately 2 times the cooking power. The
“surge power” of the inverter should be 2 times the electrical power (i.e., 4 times the
cooking power). Please note that the surge power of the microwave is not as long as the
motor load and hence, the surge power of the inverter can be considered to determine
adequacy of meeting the starting surge power
Powering a water supply pump
A water well or pressure pump often places the greatest demand on the inverter. It
warrants special consideration. Most pumps draw a very high surge of current during start
up. The inverter must have sufficient surge capacity to handle it while running any other
loads that may be on. It is important to size an inverter sufficiently, especially to handle
the starting surge (If the exact starting rating is not available, the starting surge can be
taken as 3 times the normal running rating of the pump). Oversize it still further if you
want it to start the pump without causing lights to dim or blink.
In North America, most pumps (especially submersibles) run on 240 VAC, while smaller
appliances and lights use 120 VAC. To obtain 240 VAC from a 120 VAC inverter, use a
120 VAC to 240 VAC transformer. If you do not already have a pump installed, you can
get a 120 volt pump if you don’t need more than 1/2 HP.
Idle power
Idle power is the consumption of the inverter when it is on, but no loads are running. It is
“wasted” power, so if you expect the inverter to be on for many hours during which there
is very little load (as in most residential situations), you want this to be as low as
possible.
Phantom and idling loads
Most of the modern gadgets draw some power whenever they are plugged in. Some of
them use power to do nothing at all. An example is a TV with a remote control. Its
electric eye system is on day and night, watching for your signal to turn the screen on.
Every appliance with an external wall-plug transformer uses power even when the
appliance is turned off. These little loads are called “phantom loads” because their power
draw is unexpected, unseen, and easily forgotten.
A similar concern is “idling loads.” These are devices that must be on all the time in order
to function when needed. These include smoke detectors, alarm systems, motion detector
lights, fax machines, and answering machines. Central heating systems have a transformer in their thermostat circuit that stays on all the time. Cordless (rechargeable)
appliances draw power even after their batteries reach a full charge. If in doubt, feel the
device. If it’s warm, that indicates wasted ener gy.
Page 6
CHARACTERISTICS OF SINUSOID AL AC POWER
Voltage, current, power factor, types of loads
The voltage waveform of 120 VAC, 60 Hz mains / utility power is like a sine wave. In a
voltage with a sine wave-form, the instantaneous value and polarity of the voltage varies
with respect to time and the wave-form is like a sine wave. In one cycle, it slowly rises in
the positive direction from 0 V to a peak positive value + Vpeak = 170 V, slowly drops to 0
V, changes the polarity to negative direction and slowly increases in the negative direction
to a peak negative value - Vpeak =170 V and then slowly drops back to 0 V. There are 60
such cycles in 1 sec. Cycles per second is called the “frequency” and is also termed “Hertz
(Hz.). If a linear load is connected to this type of voltage, the load will draw current which
will also have the same sine wave-form. However, the peak value of the current will depend
upon the impedance of the load. Also, the phase of the sine wave-form of the current drawn
by the linear load may be the same or lead / lag the phase of sine wave-form of the voltage.
This phase difference determines the “Power Factor (mathematically = the cosine of the
phase difference)” of the load. In a resistive type of load (like incandescent lamps, heaters
etc) the sine wave-form of the current drawn by the load has 0 phase difference with the sine
wave-form of the voltage of the AC power source. The Power Factor of a resistive load is
unity (1). The rated output power (in Watts) of the inverters is normally specified for
resistive type of loads that have unity (1) Power Factor. In a reactive type of load (like
electric motor driven loads, fluorescent lights, computers, audio / video equipment etc), the
phase of the sine wave-form of the current drawn by the load may lead or lag the sine waveform of the AC voltage source. In this case, the power factor of reactive loads is lower than
unity (1) – generally between 0.8 and 0.6. A reactive load reduces the effective wattage
that can be delivered by an AC power sour ce
RMS and peak values
As explained above, in a sine wave, the instantaneous values of AC voltage (Volt, V) and
current (Ampere, A) vary with time. Two values are commonly used – Root Mean Square
(RMS) value and peak value. For simplicity, RMS value can be considered as an average
value. Mathematically, Peak Value = 1.414 x RMS value. For example, the 120 VAC, 60
Hz. mains / utility power is the RMS value. The peak value corresponding to this is = 1.414
x 120 = 170V.
The values of the rated output voltage and current of an AC power source are their
RMS values
AC power – Watts / VA
The power rating of an AC power source is designated in Volt Amperes (VA) or in Watts
(W)
Power in Volt Amperes (VA) = RMS Volts (V) x RMS Amps (A)
Power in Watts = RMS Volts (V) x RMS Amps (A) x Power Factor
NOTE : The rated power of the inverter in Watts (W) is normally designated for a linear,
resistive type of load that draws linear current at unity (1) power factor. If the load is
linear and reactive type, the rated power of the inverter in watts will be limited to its
normal rated power in watts (W) x Power Factor. For example, an inverter rated for
1000 W ( at unity power factor) will be able to deliver only 600 watts to a reactive type
of load with a power factor of 0.6
Page 7
ADVANTAGES OF A PURE SINE-WAVE INVERTER
OVER A MODIFIED SINE-WAVE INVERTER
The output voltage of a sine-wave inverter has a sine wave-form like the sine wave-form
of the mains / utility voltage. In a sine wave, the voltage rises and falls smoothly with a
smoothly changing phase angle and also changes its polarity instantly when it crosses 0
Volts. In a modified sine wave, the voltage rises and falls abruptly, the phase angle also
changes abruptly and it sits at 0 Volts for some time before changing its polarity. Thus,
any device that uses a control circuitry that senses the phase (for voltage / speed control)
or instantaneous zero voltage crossing (for timing control) will not work properly from a
voltage that has a modified sine wave-form.
Also, as the modified sine wave is a form of square wave, it is comprised of multiple sine
waves of odd harmonics (multiples) of the fundamental frequency of the modified sine
wave. For example, a 60 Hz. modified sine wave will consist of sine waves with odd
harmonic frequencies of 3rd (180 Hz), 5th (300 Hz.), 7th (420 Hz.) and so on. The high
frequency harmonic content in a modified sine wave produces enhanced radio interference, higher heating effect in motors / microwaves and produces overloading due to
lowering of the impedance of low frequency filter capacitors / power factor improvement
capacitors.
Advantages of sine-wave inverters:
• The output wave-form is a sine-wave with very low harmonic distortion and
clean power like utility supplied electricity.
• Inductive loads like microwaves and motors run faster, quieter and cooler
• Reduces audible and electrical noise in fans, fluorescent lights, audio amplifi-
ers, TV, fax and answering machines
• Prevents crashes in computers, weird print outs and glitches in monitors
Some examples of devices that may not work properly with modified sine wave and may
also get damaged are given below:
• Laser printers, photocopiers, magneto-optical hard drives
• The built-in clocks in devices such as clock radios, alarm clocks, coffee
makers, bread-makers, VCR, microwave ovens etc may not keep time correctly .
• Output voltage control devices like dimmers, ceiling fan / motor speed control
may not work properly (dimming / speed control may not function)
• Sewing machines with speed / microprocessor control
• Transformer-less capacitive input powered devices like (i) Razors, flashlights,
night-lights, smoke detectors etc (ii) Re-chargers for battery packs used in hand
power tools. These may get damaged. Please check with the manufacturer
of these types of devices for suitability
• Devices that use radio frequency signals carried by the AC distribution wiring.
• Some new furnaces with microprocessor control / Oil burner primary controls
• High intensity discharge (HID) lamps like Metal Halide lamps. These may get
damaged. Please check with the manufacturer of these types of devices for
suitability
• Some fluorescent lamps / light fixtures that have power factor correction
capacitors. The inverter may shut down indicating overload
Page 8
AC POWER DISTRIBUTION AND GR OUNDING
CAUTION! PLEASE NOTE THAT THE AC OUTPUT CONNECTIONS AND THE DC
INPUT CONNECTIONS ON THESE INVER TERS ARE NOT
CONNECTED (BONDED) TO THE METAL CHASSIS OF THE
INVERTER. BOTH THE INPUT AND OUTPUT CONNECTIONS ARE
ISOLATED FROM THE METAL CHASSIS AND FROM EACH OTHER.
SYSTEM GROUNDING , AS REQUIRED BY NATIONAL / LOCAL
ELECTRICAL CODES / ST ANDARDS, IS THE RESPONSIBILITY OF THE
USER / SYSTEM INSTALLER.
Conductors for electrical power distribution
For single phase transmission of AC power or DC power, two conductors are required
that will be carrying the current. These are called the “current-carrying” conductors. A
third conductor is used for grounding to prevent the build up of voltages that may result
in undue hazards to the connected equipment or persons. This is called the “non currentcarrying” conductor (will carry current only under ground fault conditions)
Grounding terminology
The term “grounded” indicates that one or more parts of the electrical system are
connected to earth, which is considered to have zero voltage or potential. In some areas,
the term “earthing” is used instead of grounding.
A “grounded conductor” is a “current-carrying” conductor that normally carries current
and is also connected to earth. Examples are the “neutral” conductor in AC wiring and
the negative conductor in many DC systems. A “grounded system” is a system in which
one of the current-carrying conductors is grounded
An “equipment grounding conductor” is a conductor that does not normally carry current
(except under fault conditions) and is also connected to earth. It is used to connect the
exposed metal surfaces of electrical equipment together and then to ground. Examples are
the bare copper conductor in non-metallic sheathed cable (Romex ®) and the green,
insulated conductor in power cords in portable equipment. These equipment-grounding
conductors help to prevent electric shock and allow over-current devices to operate
properly when ground faults occur. The size of this conductor should be coordinated with
the size of the over-current devices involved
A “grounding electrode” is the metallic device that is used to make actual contact with the
earth. Other types of grounding electrodes include metal water pipes and metal building
frames.
A “grounding electrode conductor” is the conductor between a common single grounding
point in the system and the grounding electrode
“Bond” refers to the connection between the “grounded conductor”, the “equipment
grounding” conductors and the “grounding electrode” conductor. Bonding is also used to
describe connecting all of the exposed metal surfaces together to complete the equipment-grounding conductors.
Page 9
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