FAQs

An Inverter functions by converting the Alternating Current (AC) input to Direct Current (DC) in the converter charger circuit and reconverting to AC in the inverter circuit. Batteries are connected in parallel to the input of the Inverter and instantaneously come on when the Ac supply fails.

An Inverter has the following key elements.

• Mains Power sensing circuit: When the AC power comes below 110VAC or above 280VAV or if there is a total mains failure, the system automatically switches to the back-up source of power.
• Battery Charger: A module that charges the battery when AC comes and prepares battery to give back up energy in case of mains power failure.
• Inverter (DC to AC Converter): A system that would convert the energy stored in the battery/batteries to give back-up power to appliances i.e 230VAC 50Hz.

The smooth Dc power (battery power) is inverted by two channels of Mosfets (switching device) in push -pull/bridge configuration. The switching device (Mosfets, IGBT’s or Transistors) is used and controlled by sophisticated control circuit. A closed loop voltage feedback control is used to keep the output voltage constant under widely varying DC voltage (Batteries) conditions and the load on inverter. A proportional increase in the width of the pulses causes an increase in voltage and a proportional reduction in width decreases the voltage. This means the voltage control action of variable gain is normally accomplished by varying pulse width to the power.

This method of varying pulse width is known as pulse width Modulation (PWM) controls.All mode of Afriipower inverters provide regulated output voltage (PWM Controlled) on battery modeas per the load distribution voltage standard.

Fast Mains Power Sensing circuits:

In case of power failure, a good inverter would switch to battery for backup so fast that the time of switching is not to be perceptible. As a result, some appliances that required a higher start current, like the refrigerator can be driven using Inverter.

Battery Charger System:

Battery is the life of the Inverter. An Inverter lives on battery, so it is the responsibility of the inverter to protect the battery and use it optimally and enhance its life. Inverter battery lifetime is maximized if the battery is always powered from a constant current charger. AfriipowerInverter gives constant charging current to batteries irrespective of the AC voltage i.e whether the AC voltage is 150 or 270V, the battery gets nearly the same charging current. This protects the battery plates from damage and Afriipower Inverter has an advanced trickle charging mechanism built in the system to prevent batteries from overcharging and to increase the battery life.

Inverter (DC to AC Inverter):

The main part of the inverter system, one that converts battery energy to backup power must be designed to deliver high grade power most efficiently. Afriipower Inverter is designed to perform this function in the absence of power.

The power from the mains is a sinusoidal wave (Sine wave) of frequency of 50Hz. Ideal Backup power source would be one that generates the equivalent sine wave of the same as that of the mains. Afriipowerrange of power Inverters give power in the form of stepped sine wave (Quasi Sine Wave) voltage so that the bulbs &Tube lightsglow at an optimal brightness without any humming sound.

In fact, most of the times it is difficult to realize the absence of main power. Afriipower inverters voltage regulations in the inverter are very good. So, the output voltage (on battery mode) would remain nearly constant irrespective of battery condition and load on the Inverter.

Square Wave produce the humming sound and reduce the life of the appliances. In most of the Transistor power inverter, Output is the square wave on battery mode.

Afriipower Inverter produces the stepped Sine Wave (Quasi Sine Wave) which is nearly equivalent of the AC Main Sine Wave and gives the same results.

Overload Protection with Auto-resetting:

As you apply load (bulb, fan, tubes etc.) more than inverter capacity (during Inverter on Condition), It will warn you with Beep Sound & LED indication, in this situation the system will shut down Output for a few seconds and then start to check the load on Inverter, and do this process again & again untilyou don’t reduce the load & when the loads become within the capacity of the Inverter, the Inverter will stop beep sound and off the OVERLOAD indication and will supply the power to your appliances automatically.

Low Battery / Deep Discharge Protection:

The Battery must be protected from discharging completely. Lead Acid batteries/ SMF/ Tubular batteries should not be discharged below a certain threshold level. The battery deep dischargeProtection is required because a deeply discharge battery is difficult to recharge. Afriipower’s range of power Inverters have the low Battery/ deep discharge.

Battery Overcharge Protections:

Over charging occurs when battery continues to get charged with high value of current after getting fully charged. Such charging corrodes the battery plates and reduce the battery life.

Hence battery-Overcharging protections is necessary because if battery is getting over charged frequently, then it will reduce the life of the battery. Afriipower Inverter models have the Battery Overcharge Protection.

Short Circuit Protection:

A good Inverter must also protect itself from damage. Since anInverter is a Consumer product and is connected on house wiring, chance of risk must be minimized. It must have a built-in short circuit protection, so that if any equipmentconnected across it were to be short circuited, the Inverter itself should not get damaged due to drawing high current.

The Afriipower inverters come with fuse free, Electronic short circuitprotection. This would prevent damage to the inverter as well as the other appliances attached to it.

Reverse Battery Protection:

It means when the batteries to inverter connected in reverse (i.e+of battery to -ve of batteries to +ve of inverter), The system should not damage. Afriipower inverters have the same protections.

Frequent Stability:

Many Appliances are by design dependent on the frequency of the input power (normal input supply frequency (50Hz +/- 5%). The output wave from the inverter should be stable (50Hz) for proper functioning of these equipment’s.

The frequency stability of Afriipower Inverters is achieved by PWM (pulse width Modulation) controller, which delivers stable high grade of power. This controller also ensures frequency stability with temperature to the tune of 2%.

CCCV Battery Charger:

Inverter battery lifetime is maximized if the battery is always powered from a Constant Current Constant Voltage (CCCV) charger.

AllAfriipower Inverters are designed for the hostileNigerian conditions. The charger of inverter is deigned on the silicon-controlled rectifier Technology (acknowledged as the best technology for battery charging), because of which power consumption is minimum and give constant charging current to batteries irrespective of A.c voltage is 145 or 220V, the battery gets nearly the same charging current through the CCCV charger.

High Efficiency of System:

The efficiency of the Inverter system is calculated by comparing the input power with the output power in the Inverter/Battery mode of Operation. A device that has a high switching speed can only achieve maximum efficiency. MOSFET is a high speed -switching device.

Afriipower Inverter design is based on MOSFETS. The design has an Inverter efficiency of 95% and overall efficiency of nearly 92%. This results in more backups with less stress on batteries.

The Inverter usually comprises of a power circuit which is switched at a pre-determined frequency to generate stepped wave. There are various types of devices used in the inverter power circuit. Earlier technologies used bipolar junction transistors or BJT’s (1960’s) and power transistor (1970’s). The latest generation devices are power MOSFET’s which have revolutionizedinverter technology and offer unique advantages over conventional devices.

MOSFET’s are majority carrier, voltage-driven devices and their construction and principles of operation are fundamentally different from BJT’s, which are minority carrier, current-driven devices.

MOSFET’s offer several significant advantages over thyristors as well, which include the ability to operate at frequencies above the audible range, low output distortion, high overload capability, negligible switching and snubber circuit losses, fast response and simple drive circuitry.

Device characteristics limit the use of BJT’s for high frequency switching applications. Minority carrier delay times limit the switching speed to the 500 to 5000 nanosecond ranges. MOSFET’s on the other hand, are the majority carrier devices and switch in the 20-100 nanosecond range. Conventional inverter systems have an efficiency range of 60-80%. MOSFET based systems with inverter efficiency as high as 92.5%.

How is this Increase in Efficiency Obtained:

Losses in the inverter circuit are primarily switching losses, snubber losses and 12R losses. Use of MOSFET’s practically eliminates the first two losses. Unlike BJT’s, MOSFET’s are majority carrier devices having no storage time effects. Switching losses are directly proportional turn- on and turn-off times, for MOSFET’s, are in the nanosecond range, practically eliminating switching losses.

Further, MOSFET’s switching performance is essentially independent of operating temperature, unlike BJT’s wherein efficiency drops as temperature increases with switching times.

Snubber are resistive devices used in inverter power circuits to control the rate of rise of voltage caused by rapid switching. MOSFET’s have a very high dv/dt rating (in the range of 1000 to 2000 volts/microsec) eliminating the need for snubbers altogether. BJT’s, on the other hand, have DV/DT Limited to about 200 volts/micro sec. Such turn-off times need very heavy snubbers across the devices, resulting in losses.

As result of this increase in efficiency, for the same capacity battery, MOSFET based inverters ensure longer backup time and lower AH batteries can be used, thereby reducing battery cost.

Surge currents are normally generated at the time of switching on equipment, sudden changes in load, etc. for instance, a refrigerator draws up to eight times its normal current draw during start-up. MOSFET-based inverters can handle higher inrush currents.

Afriipower inverter design is based on MOSFET’s. The design has an inverter efficiency of nearly 92%. This results in more back-up with less stress on the batteries.

An uninterrupted power supply (UPS) is a system intended to solve the main disturbances and main failure. The batteries attached to the UPS system enable the user to work during main failure. This is done by putting the UPS system between the mains and your computer.

OFF-LINE UPS SYSTEMS

The OFFLINE UPS SYSTEM supplies (or routes) the incoming mains supply directly through to the output usually through a relay contact. Some high frequency noise filtering and surge suppression may be included in this path. The UPS system switches on its inverter as soon as main supply failure is detected or below the normal load and simultaneously switches the output relay to the inverter side to supply battery sourced power to the load. The transition involves a delay on account on the time to reliably detect mains failure and switch over a relay, and the output is broken for this period (usually for 2 to 12m sec).

OFF-LINE UPS SYSTEM is usually the least expensive as compared to the other two.

LINE INTERRACTIVE

The true LINE INTERACTIVE design is in fact a combination of OFFLINE & ONLINE, in which the inverter plays a dual role of Charging the battery when mains supply is present as well regulating output voltage and working as a normal inverter in absence of mains supply, so to the user it appears like an ONLINE System. Line Interactive UPS system offers enhanced power protection over the basic Offline designs by providing additional line conditioning.

ONLINE UPS SYSTEM

An ONLINE UPS SYTEM is the one in which the inverter always supplies power to the protected load and hence the same quality of power is ensured all the time. Whenmains supply is present, the inverter derives its power from the mains supplied rectifier and the backup batteries are also kept in charged state. When the mains fail, the source of DC power for the inverter section shifts to the battery without any break whatsoever in the output to the inverter. It also bears all the vagaries and borne out of the mains supply and insulates the secure bus supply from it.

An ONLINE SYSTEM is especially useful for sensitive and critical equipment/devices.

As an experienced & Conscientious Computer user, you have faith in the dictum GIGO and you take precautions to see that ‘garbage’ doesn’t enter your system through software. But there is one more source of garbage, of a more serious nature, which is not normally taken care of. That is in the form of garbage power input to the computer. It is more serious because besides malfunctioning and operation problems it can also cause permanent damage to your computer.

It is common knowledge that there are fluctuations in utility supply, for example, sometime the utility voltage is as low as 170 to 160 volts and high as 280 to 300 volts. Besides this, there are many more hidden culprits associated with utility lines like sags and surges, oscillatory transients, EMI and RFI, brown outs, or total loss of power.

The equipment to which you are feeding this power is extremely sensitive to the quality of power and is termed as critical equipment. Imagine a sudden failure of computers during busy hours when a critical operation is in progress. All this can occur due to garbage power fed to such equipment. The loss is invaluable, and you just cannot take any chances.

The above problem is of malfunctioning or operational nature. These can be extremely frustrating, time consuming and expensive. Besides, like all electroniccircuits can also undergo irreparable damage due to high voltage surges and spikes, which can reach several kilovolts.

The important blocks in a UPS system and their functions are listed below: These shall be helpful in explaining the functioning of the UPS system.

LINE FILTER:

Eliminates line borne noise and spikes.

INVERTER:

The smooth DC is inverted by two transistors connected in push-pull configuration. The switching device (Transistor or IGBT or MOSFETS) is used and controlled by a sophisticated control circuit. A closed loopvoltage feedback control is used to keep the output voltage constant even under widely DC voltage conditions. A proportional increase in the widths of the pulses causes an increase in voltage and a proportional reduction in width decreases the voltage. This means that the voltage control action is a great advantage for taking care of dynamic loading conditions in a computer like switching on and off disk and tape drives as well as movement of the accessing head. Current feedback protects the inverter even from short circuit by turning off the control pulses going to the transistor/IGBT/MOSFET base.

OUTPUT FILTER:

The output filter converts the inverter output to a smooth AC with very low distortion. The nature of the filter is such that it can deliver inrush and surge currents demanded during switching on of computer loads.

The protected computer system, or “critical Load”, is always powered by the inverter. The inverter is what changes DC power from the rectifier or battery into AC current. This is called “double conversion” (AC to DC, then DC to AC). The protected system is always isolated from input variations (frequency and voltage). These variations are often caused by reduction in electrical voltage from the power utility described as sags or brownouts, or from variations created by auxiliary power sources such as generators.

A UPS System Traditionally can Perform the following Functions:

• Absorb relatively small power surges.
• Smooth out power sources.
• Continue to provide power to equipment during line sags.
• Provide power for some time after a blackout has occurred. In addition, some UPS system or UPS/software combinations provide the following functions.
• Automatic shutdown of equipment during long power outages
• Monitoring and logging of the status of the power supply
• Display the voltage/current draw of the equipment.
• Restart equipment after a long power outage.
• Display the voltage currently on the line.
• Provide alarms on certain error conditions.
• Provide short circuit protection.

Online UPS provides better overall protectionto your computers and peripherals.This protection includes Power conditioning, regulated voltage and frequency and zero transfer time to battery during mains failure.

A pure sine waveform has a peak value, which is 1.414 times the PRM value.

A resistance or any linear load connected to such a voltage source draws current having similar waveforms and hence has a crest factor of 1.4.

As against this, the non-linear loads may demand currents whose peak values to RMS ratios are 2 to 5 or more. This ratio of peak to RMS is termed as the crest factor and is indicative of the degree of non-linear load capability of the UPS System.

A regulated voltage source such as invertersection of ON-LINE UPS SYSTEM is expected to maintain the voltage at a predefined level, irrespective of changes in supply, i.e DC input voltage or load current levels. The percentage deviation of the output, as a result of load or dc input change, after the output voltage has settled to a new level is defined as the static or steady state regulation.

Afriipower Inverter produces the stepped Sine Wave (Quasi Sine Wave) which is nearly equivalent of the AC Main Sine Wave and gives the results.

The percentage deviation of the output from its steady state value immediately following a disturbance such as change of DC supply voltage or load current is termed as dynamic/transient regulation.

This deviation is generally much larger than the steady state value specified as voltage regulation, and incidentally is a measure of the speed of response of inverter control system. Since by definition this is a transient quantity, not only the deviation but also the time to bring the voltage back to the steady state regulation level is also an important index of performance.

Despite significant advances in its production & distribution, the main AC supply is subject to regular fluctuations, some of which can pose a significant threat to the integrity and continuity of computer operations.

• Voltage spikes and surges
• Micro cuts
• Brown outs or voltage sags
• Noise

That’s a good question, and one is worthy of some debate. One school of thought holds that one should always run equipment on the best approximation of sinusoidal input that one can, and that deviations produce harmonics which may either be interpreted as signal if they get through a power supply or may actually damage the equipment.

Another school holds that since almost all computers switching-type power supplies, which only draw power at or near the peak of the waveforms, the shape of the input power waveform is not important.

 Our Opinion is that sinusoidal output is worth the extra money, especially for on-line UPS systems that continually provide their waveform to the computers.

To satisfy the requirements of various applications and from the viewpoint of criticality in operations, different topologies are employed in ONLINE UPS SYSTEM.

HOT STAND TYPE CONFIGURATION

This configuration comprises of two units of UPS’s (named UPS1 & UPS2). When UPS1 is delivering power to the load, UPS2 remains idle.

In case of failure in the inverter of UPS1, static switch is enabled thereby providing uninterrupted power to the load through UPS2. UPS1runs in synchronism with UPS2, ensuring no break transfer from UPS1 to UPS2. Under healthy conditions, the batteries get charged through corresponding rectifiers.

Most certainly, a number of devices in various computer installations are studied, information is collected from device manufacturers and after taking all this into account the system is designed. Afriipower has been doing this work in close Co-operation with experienced people from computer application and computer maintenance fields. Therefore, Afriipower is in a position to offer its users a unique advantage over others.

There are three ways in which we approach this. Check the plate at the back of the equipment near the main outlet, it will usually give a figure in watts(W) or Amps(A). If in Amps, multiply the line voltage by the figure given to arrive at a VA (Volt Amp) rating add 25% which is what UPS system are rated in.

Battery selection depends upon the backup time required which in turn depends upon the frequency of power failure, average Programme length and the presence of other back up source like a dieselgenerator set. One thing to remember is that the ampere hour ratings quoted by battery manufacturersare on a ten-hour discharge basis and normally the backup time required will be much shorter; sufficient either to finish an almost complete job or to take a systematic shut down or to start the generator set. However, when the battery is discharged in a shorter time a derating factor has to be used which incidentally does not vary below 20 to 30 minutes. So approx. half an hour is a sensible back up time to select.

Battery life depends upon a number of factors, viz

• Temperature
• Number of discharges experienced.
• Number of deep discharges experienced.
• Specification of the batteries

Battery life is halved for every 10 degrees centigrade increase above its specified operating temperature (usually 25 degree centigrade).

UPS system batteries are designed for maximum life in typical use i.e long periods of continuous low change and occasional minor discharges.

At installation time, the battery is at 100 percent of rated capacity. Each discharge and subsequent rechargereduce the relative capacity of the battery by a small percentage. The length of the discharge cycle will determinethe reduction in battery capacity. So-called deep discharges on a repeated basis will reduce the life of the battery.

The “loaf of bread” analogy is most often used to illustrate the relationship between cycling and battery life. A loaf of bread can either be cut into many thin slices or a few thicker slices. Similarly, a UPS system battery can provide power over a large number of short cycles or fewer cycles of long duration.

The IEEE defines “end of useful life” for a UPS system battery as being the point when it can no longer supply 80 percent of its rated capacity in ampere hours. The relationship between amp-hours and protection time is not linear, a 20% reduction in capacity results in a greater reduction in protection time. For example, a UPS system that supports a full load for 15minutes when new, will support the same load for only about 8minutes when it reaches its defined “end of  life”.

When your battery reaches 80% of its rated capacity, the aging process accelerates, and this is the time when the battery should be replaced.

No UPS system battery will last forever- even one that experiences minimal use. This is because UPS system batterie are Electro chemical devices whose ability to store and deliver power slowly decreases over time. So, even if you follow all the guidelines for proper storage temperature and maintenance, you still must replace them after a certain period of time.

If the batteries are less than 12 months old,then the failure could be due to a material fault. In this instance, the failed battery can be replaced after confirmation by testing the whole battery bank.

In general, once the batteriesare 12 months old, the failure is more likely to be due to age, environment or usage and the whole bank should be replaced. Failure to replace the whole bank could result in the new battery not being charged properly and your load being at risk if any or all of the older batteries fail.

• Gradual decrease in battery life can be periodically monitored and evaluated by: Voltage Checks
• Load testing.
• Checking for proper battery connection
• Checking for battery water (in case of Automative Batteries)

Without regular maintenance and service checks, your UPS system battery may experience:

• Heat- generating resistance at the terminals.
• Improper loading
• Reduced protection
• Premature failure or reduced backup

As long as the batteries are fully charged when the unit is switched off, they will not require charging for three months.

The cold start feature of the power pack Line Interactive UPS system isolates the batteries from the UPS system circuit and thus the UPS system can be switched off for a longer period (six months) without damaging the batteries.

Following parameters should be considered before buying a UPS/Inverter System

• Company reliability, experience, stability, customers services.
• Technology and features.
• Price and performance.

Recharge the UPS system for at least 8hrs before the first operation. Every UPS system passes the quality examination before it is shipped out of factory. These QC parameters consume the battery power of UPS system. We strongly suggest users to recharge the UPS system before using it at every first time to make sure that battery is fully charged condition.

One is right when one says “similar”. The reason is that the equipment manufactured by Afriipower uses pulse width modulation technique with transistor/IGBT/MOSFET as the basic inversion element. There is no chance of the fuse blowing during sudden load application due to commutation failure. That means less down time and assured power supply. Due to PWN technique the size of the filter is also small which further improves the dynamic behavior.

We guarantee an inversion efficiency of more than 90- 92%. High efficiency also results in smaller size. Our equipment is the smallest for a given rating, it occupies minimum floor space and can be installed very easily. A very generous design imparts tremendous, short term overload capacity to our equipment which is to take care of large inrush and surge currents demanded by computer devices.

Apart from the fact that we are able to obtain a single functionally efficient system (Home UPS) in lieu of the existing two systems (Inverter and UPS), there is also the element of saving the cost of the battery of the UPS. Additionally, the sine wave home UPS of Afriipower has a high input power factor during charging (0.9) and pure sine wave output (harmonic distortion <3%). Hence, one will save on the quantum of electricity required for actually charging the battery while having the facility of much better quality and distortion free power.

The plate grids are the vital elements of the battery. There are two types of plates- positive plates and negative plates. The positive plates consist of a grid over which active lead peroxide is placed. This dark brown crystalline material has a high degree of porosity in order to allow the electrolyte to penetrate the plate freely. Negative plates are grids plated with a type of lead referred to as sponge lead, which is simply finely ground lead. Grinding the lead allows the electrolyte to penetrate the grid.

There may be any number of plates used in a battery; it all depends on how much energy you want to store. The more plates (or the larger the plates), the more energy the battery can store and release. The negative plates will always outnumber the positive plates by one for reasons of improved performance.​