An Inverter is a system that provides backup or convert the D.C stored in battery to A.C when the electrical power fails or drops to an unacceptable voltage level & when Electric power present, it charges the battery or convert A.C to D.C and store it into battery.
There is no difference in the working of Inverter & Home UPS. Both convert A.C. to D.C. when mains is present & charge the attached battery and convert D.C. to A.C. when mains is absent & run all the connected appliances.
Only there is a slight difference in the technical parameters. In UPS the time of change over time from mains to back-up & back-up to mains is less than Inverter so if some sophisticated equipments (e.g. Computers) which should not get rebooted if mains absent, running on it will not get affected. In our Home UPS / Inverter, the changeover time in case of UPS is 10-15msec. & in case of Inverter is 30-40msec. (1msec. is 1/1000th part of a sec.)
TTo know Home UPS we should first know what Inverter is.
Inverter is an old product which was used to power mainly light bulbs, tube lights and fans. When the mains failed, the changeover time of the inverter from mains power to internally generated power was long. This resulted in the lights connected at the output to turn off and then turn on again. It was not possible and also not advisable to connect a computer to an Inverter as it would turn off and reboot when the mains failed. This was likely to corrupt the data stored in the computer and also possibly damage the computer hardware.
In contrast to this, a Home UPS has a range of features which make it safe to connect a computer to it. In addition to other house hold electrical appliances like electric bulbs, fans, tube lights, CFL bulbs and TV. The changeover time from mains to internally generated power is so short that the computer will keep running without interruption. So you no longer require a separate UPS for your computer. PEPTELLER Home UPS can be your sole power back-up solution for your home, office or shop.
Inverters and Home UPS products currently available in India use one of the following technologies. (Note that the description given below applies precisely to PEPTELLER Home UPS products. For other brands, it may not apply fully).
If the output of the Digital Home UPS is connected to an oscilloscope (an instrument which is used to visually display the variation of voltage with time), it will look as shown below:
As we can see, at some points, the output voltage rises or falls rapidly. In normal Home UPS products this gives rise to noise in fans and chokes of the tube lights. PEPTELLER has added a filter circuit to reduce this noise to the maximum extent.
Most Home UPS products use a microcontroller to control all its functions. In this design all functions are embedded into a single integrated circuit (microcontroller). Use of microcontroller has the following advantages:
Reliable operation
Easy testing, and troubleshooting`
Good serviceability
Ease of future up-gradations
Digital Home UPS uses two banks of MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) to drive the step-up transformer which delivers the output power. It is important that the pulse width (turn-on time) of the MOSFETs is controlled precisely in each half cycle depending on the battery voltage and load at the output. This is necessary to maintain constant voltage at the output. You should check that the Home UPS delivers nearly constant voltage over the full range of battery voltage (from fully charged to discharged state) and from small load to full load.
Battery charging in Digital Home UPS products is achieved using phase control of a triac device. The charging current should be controlled based on the battery charging current and should vary with the terminal voltage of the battery. If the charging voltage is too low the battery will not charge fully and will not be able to give the desired back-up time. On the other hand too high charging voltage will reduce battery life and may even damage it. If the charging current is too low, it will take a long time to charge the battery.
AIf the output of the pure sine wave Home UPS is connected to an oscilloscope, it will look as shown below:
As we can see, the voltage varies smoothly with time. Hence there is no noise in the fans or chokes of the tube lights. This wave shape is similar to that of the mains supply available from the electricity company. It is recommended to use pure sine wave Home UPS for sensitive electronic instruments like music system. Sine wave Home UPS products generally use a microcontroller to control all its functions intelligently.
Four banks of MOSFETs are driven with PWM (Pulse Width Modulated) waveform to generate pure sine wave at the output. This four MOSFET bank design (also called full bridge drive) is inherently more reliable than the two MOSFET bank (also called half bridge drive or push-pull drive). Another important factor is the PWM frequency. Higher frequency results in smoother wave form.
Digital Signal Processor is an advance microcontroller with higher and more sophisticated processing power. It is generally used in Home UPS products of capacity of 2KVA and above.
The output waveform and other features of the DSP sine wave Home UPS is nearly same as the output of the normal sine wave home UPS. However the switching frequency is around 20 KHz (above the frequency range of human hearing) so that the Home UPS itself is completely noiseless.
In all the technologies described above, the power transfer from the battery side (low voltage: 12 / 24 Volts) to high voltage side (230 Volts 50 Hz A.C.) is achieved using an iron core transformer. This transformer is a bulky item and constitutes a major cost element in the whole design. With advancement in semiconductor technology, a new technology is emerging in the Home UPS field. This is called High Frequency technology. In this technology, the power transfer from the battery side to high voltage side is achieved by switching the MOSFETs and IGBTs (Insulated Gate Bipolar Transistor) devices at very high frequency. This allows the use of a much smaller ferrite core transformer. As yet, this technology has not proved itself in India and is in trial stage.
O/P of Square wave Inverter is a square wave, which having sharp peaks, due to these peaks, some time a negligible sound can be heard from Tubes & Fans. But the O/P of Sine wave Inverter is Sine wave which is similar to Mains so appliances work normally on Inverter also without any sound.
DSP stands for 'Digital Signal Processing'. This is a technology to produce a sine wave better than using Microcontroller. For this, DSP Processors (DSP I.Cs.) are available in the market. These are highly efficient and fast processors that enable us to produce better sine wave.
While purchasing an Inverter always keeps the minimum load, you want to run on the Inverter & ask the following things to the Inverter Dealer:
Tell him minimum load requirement, you want to run on the Inverter & ask the particular model available with him.
Ask him whether that is a Home UPS, if you want to run your computer on Inverter. Computer should run with out Rebooting while Changeover Mains to Battery & Battery to Mains.
You should ensure that it is based on a microcontroller and not on old discrete ICs (Integrated Circuits).
Know the Capacity of Battery Compatibility and on full charged Battery, how many hours it will give the back up. (If you select 600VA, it should give ≥ 3hrs backup on full load with 150AH Battery & if you select 800VA it should give ≥ 2.5hrs backup on full load with 150AH Battery.)
The ‘No Load Current’ of the Inverter. It should be ≤ 1.5A.
Ask him if it has ‘High Mains Voltage Protection’ & ‘Automatic Holiday Mode’ feature.
Ask him if it has protection against, ‘Overload, Short Circuit & Reverse Battery’.
Lastly, ask about the Battery Charger in the Inverter. It should we smart three stage Battery charging Charger or Fuzzy Logic Charger.
There may be different issues in different Local Products available in several areas. It is not necessary that you find all the drawbacks in single inverter, but it is always possible that you find few of different drawbacks mentioned below in any Local Inverter.
You should ensure that Home UPS is based on a microcontroller Technology and not on old discrete ICs (Integrated Circuits), which many of the local products are using.
The ‘No Load Current’ of the Inverter which should be ≤ 1.5A, is always very high in Local products, resulting Battery discharge during Power fail mode even when no Load is running on Back up mode
Ensure protection against, ‘Overload, Short Circuit & Reverse Battery’ which many of the Locals do not have within them
Ensure ask about the Battery Charger in the Inverter. It should we smart three stage Battery charging Charger or Fuzzy Logic Charger, apart from this many local products do not charge on Mains below 150 V.
Ensure High Battery Cut and Low Battery voltage cut present in Branded ones, without which there is big risk of Battery getting discharged during prolonged power cuts in many of the Local products
Ensure Home UPS Model, which is frequently not available in Local Products.
As computer has become quiet a common product and is generally used at Homes or being planned to go for the same in near future
Ensure High current charging mode and normal charging mode, which is quiet useful in areas where there are long power cuts, and generally not available in local products
If your Appliances make sound on Inverter O/P, it will surly be a Quasi Sinewave Inverter. The O/P of a Quasi Sine wave Inverter is like as follow:
As we can see, at some points, the output voltage rises or falls rapidly. In normal Home UPS products this gives rise to noise in fans and chokes of the tube lights.
But our appliances are made to work on Sine wave as follow:
So if you want, your appliances should not make sound on Inverter. The Inverter should be of Sine wave Technology.
The O/P of Generator is Square wave with Varying Voltage from 100V to 300V & frequency range varies from 30 - 60Hz, while most of Inverters are made to work on Voltage varying 140V to 270V & Frequency 45Hz to 55Hz. So if the voltage of generator is below 140V or above 270V & Frequency of Generator is in between 30 – 40Hz, Inverter will not charge the Battery.
At the time of charging, our Inverter pay a load of 185W/Hr. on Mains & efficiency is 54% in case of our Inverter so from this we can calculate that in continuous charging for 10Hr., our Inverter consumes 1 Unit of Electricity.
Yes, if it is Home UPS then you can run your computer on Inverter. In case of Square wave Home UPS, there are some loses in computer Supply but on Sine wave Inverter, you can run your computer without any worry.
Three Step Charging’ or ‘Fuzzy Logic Charging’ is a S/W controlled Intelligent Charging. It increases Battery life and save your Electricity when your Battery become old. It works as follow:-
The Boost Charging Current for a Battery of a particular AH Capacity is recommended as 1/15 the AH for better Battery Life and performance.
The Battery full charge voltage is set at 13.8V (27.6V in case of 1400VA Inverter) and Float voltage at 13.5V (27V in case of 1400VA Inverter)
Now if Battery is discharge, Inverter starts charging the Battery with the Boost Charging Current till the Battery Volt. reaches 13.1V (26.2V in case of 1400VA Inverter).
After this Volt, the Battery Current starts reducing and the Battery Voltage Continue to rise till full Charge Voltage is achieved in the timed period.
Condition 1:- If the Battery reaches its selected full charge voltage, the Battery stays at that volt for 1 Hour, or till the charging current reduces to 40% of the Boost Current, whichever is achieved first.
Condition 2:- If the Battery is unable to go up to the full charge voltage within the Constant Boost Current timed period, the Battery starts to float at the Voltage reached or float at 0.2V (0.4V in case of 1400VA) below the voltage reached in the Constant Boost Current Mode.
In the Float Mode the float current is monitored continuously. If the float current does not fall below 35% of the Boost Current after a specified period, the float voltage is reduced further, and if the float current falls below 3% of the Boost value the float voltage is increased.
As there is a 10A AC Fuse provided on back Panel for Mains (High Current precaution). If we calculate Load Capacity in Mains mode then it will be 220V * 10A = 2200Watt where 220V is O/P of Inverter. We can say it can bypass 2KVA load in Mains Mode.
The output waveform and other features of the DSP sine wave Home UPS is nearly same as the output of the normal sine wave home UPS. However the switching frequency is around 20 KHz (above the frequency range of human hearing) so that the Home UPS itself is completely noiseless.
Our Inverter does not bypass the High Voltage of Mains (above 290V) to Appliances even if 'Inverter Switch' of Inverter is 'OFF'. It remains in Back up Mode & in this condition it shows 0% Load on Inverter. If 'Inverter Switch' is ‘ON’ then in the high voltage condition, Inverter restricts the Mains & starts giving supply from Battery.
Consider the situation in which Inverter is in 'Back-up Mode' & Inverter Switch is ON but no load is paid on Inverter. In this situation Inverter circuitry Load will be present on the Battery & some current will be drawn continuously from Battery, this current is known as 'No Load Current' of the Inverter. The range of this current is 1.2 - 1.4A.
This no load current is enough to deep discharge your battery, if power is gone for 2-3 days.
To avoid this deep discharge of the Battery in the above described condition, Our Inverter having feature of 'Holiday Mode'. Our Inverter will be auto shut down if above situation occurs for = 12 hour. And if a customer wants to run load on the Inverter then he will have to switch off & on the Inverter Switch. And the Inverter will start working normally.
If Inverter is in 'Back-up Mode' & no Appliance is running on Inverter then some current always flow from battery to Inverter. This is due to 'Circuitry load' of Inverter itself. This current is called as 'No Load Current' of Inverter. For our Inverter its value is 1.2 - 1.4 A.
