A generator is a machine that converts mechanical energy into electricity. A generator generally requires fuels like kerosene, petrol, diesel, etc. Fuel is used as the source of mechanical energy. A generator is used mostly when a lot of power is required. Generally small devices do not require generator. When we want to use multiple applications or devices or equipment simultaneously for a prolonged period of time, a generator is used.
Advantages of a generator:
For a generator we do not need existing power supply or stored power supply. This means when there is no power for a very prolonged period of time or if we are in an area where no power supply is at all, a generator is very useful. A generator is very powerful so when we want to supply current to a whole building or machinery, etc. we can buy a generator according to our requirement. There are very small generators to very huge generators.
Disadvantages of a generator:
A generator usually needs to be started once the power supply goes off. This would leave power disruption between the time power supply goes off and until the generator is started.
A generator cannot be kept inside the room we work. This is because generators create lot of noise and lot of smoke pollution and they can turn out to be somewhat smelly.
An inverter helps to restore power supply almost immediately after a power failure. It has an option to automatically restore power or for manual restoration. Manual restoration can result in blanking out of power until the restoration. If an automatic restoration is there, then it might take as much as a few seconds for power restoration.
Inverter supplies power from a battery, which should already be having power and it should be recharged regularly or rather should be always on.
Advantages of Inverter:
An inverter is convenient in a small office or home setting. There are small capacity inverters as well as large capacity inverters. If power supply goes for a very small amount of time, the inverter will be useful, especially for a few hours. When power supply interruption is going to be prolonged, one can start the generator.
Disadvantage of Inverter:
If there is no power supply at all in an area, if the power in the battery is drained, then the Inverter will be of no use. Inverter can be used only for a few hours as otherwise the battery will be drained out. Battery maintanence is required. Some electronic goods like computer will get reset even if on an inverter, because there is a small disruption in power supply.
UPS stands for Uninterrupted Power Supply.
Use of UPS:
UPS prevents an electric/electronic device from getting switched off by providing uninterrupted power supply.
In an inverter, current from outside is directly supplied to your gadget. The battery is not involved. However, there is a mechanism that will check if power supply is present. Once it is detected that the power supply is not present, then immediately a change over happens and supply takes place from battery. However, the small time of 1 or 2 seconds for the detection and change over causes problems for many sophisticated electronic gadgets.
In the UPS, the supply is always from the battery. So for the gadget, it really does not matter if the main supply is present or not. The main supply is used here only to charge the battery. So only when the battery is drained does the UPS stop working.
One more advantage is UPS has protection from voltage fluctuations as the supply is from battery while for inverter the output voltage is based on input voltage.
Because of the more complicated circuitry involved, the UPS is costlier than inverter.
The advancement of technology has led to products which has a combination of the above 3 built in them. For example a backup that will act as an UPS at first and then will change to a built-in inverter or a generator by itself.