The Development Of Uninterruptible Power Supply

Uninterruptible Power Supply(UPS)
Before the era of using batteries, uninterruptible power supplies used flywheels and internal combustion engines to provide power supply for loads. This type of uninterruptible power supply is called a flywheel or rotary uninterruptible power supply. A flywheel uninterruptible power supply consists of a rectifier, a DC motor, a flywheel, a diesel engine (or gasoline engine) and a generator. When the power grid is powered, the DC power provided by the rectifier drives the motor to rotate the flywheel, and the generator is used to power the load. Due to the inertia of the flywheel, the generator speed can be kept balanced, and the uninterruptible power supply plays a role in filtering the interference of the power grid. When the power grid is cut off, the flywheel continues to drive the rotor of the generator to rotate, and at the same time, the diesel engine is started to drive the generator to generate electricity, replacing the original power grid to power the load.

Since the flywheel uninterruptible power supply uses an internal combustion engine to provide electricity, it will generate a lot of noise and is also large in size. Therefore, it is generally only used in emergency situations and some occasions with severe natural conditions. Usually, the uninterruptible power supply uses batteries to provide power.

Battery-type uninterruptible power supply
Since the 1960s, when General Electric Company of the United States began to research and produce uninterruptible power supplies, uninterruptible power supplies have been improved, but their basic principles have not changed significantly.

Modern uninterruptible power supplies consist of a battery pack, an inverter, and a control circuit, with one end connected to the power grid and the other end connected to the electrical load. When the grid voltage is normal, the uninterruptible power supply uses the grid power supply to charge itself. When the grid is abnormal, the uninterruptible power supply releases the energy stored in the battery for the load to use. It is usually divided into two types according to the working mode: online type and backup type (also called offline type); according to the output waveform, it can be divided into sinusoidal type, approximate sinusoidal type (using step square wave to fit sine wave), etc.