Power converters electronics

Static Power converters execute power conversion quite efficiently. Power electronic switches have solid-state devices with components like inductors and capacitors. Generally, inductors and capacitors exhibit negligible power loss characteristics in comparison to resistors. The classification of power converters are as follows :. We have already learned in basic electronics that the devices that convert the AC signal into DC signal are known as rectifiers. Diode Rectifiers : This rectifier circuit changes applied ac input voltage into a fixed dc voltage.

Either a single-phase or three-phase ac signal is applied at the input. These are mainly used in electric traction and in electrochemical processes like electroplating along with in battery charging and power supply. These are also used in welding and UPS related services. Phase Controlled Rectifiers : Unlike diode rectifiers, phase-controlled rectifiers are designed to convert a fixed value of ac signal voltage into a variable dc voltage.

Here line voltage operates the rectifier hence these are sometimes known as line commutated ac to dc converters.

Similar to diode rectifiers, here also the applied ac signal can be a single-phase or three-phase ac signal. Its major applications are in dc drives, HVDC systems, compensators, metallurgical and chemical industries as well as in excitation systems for synchronous machines. The converters that convert the dc signal of fixed frequency present at the input into a variable dc signal at the output are also known as choppers. Here the achieved output dc voltage may have a different amplitude than the source voltage.

The output is controlled by a low power signal that controls these semiconductor devices from a control unit. Here forced commutation is required to turn off the semiconductor device.

Generally, in low power circuits power transistors are used while in high power circuits thyristors are used. As a dual converter also consists conversion of D. C to make it work converter two is blocked, D. C inputs become load to dc power source conversion. To make thyristors conduct, a trigger pulse must be given to its gate simultaneously along with line voltage. A separate gate drive circuit must be added to a dual converter thyristor bridges Gate drive circuit must be equally synchronized with source voltage, any delay causes zero cross jitter and zero frequency fluctuates.

To prevent these circuits must be included with phase lock loops and comparators. These thyristors can be triggered through an optocoupler which is connected to a port of microcontroller.

Rotation of motor can be initialized using optocoupler by setting a set of thyristor to trigger which is placed at one side and change in direction of motor can be achieved by triggering another set of thyristor Variation in speed of motor can be achieved by delayed firing angle of SCR. Mode selection and speed selection are microcontroller interfaced switches using these switches speed and rotation can be selected.

Power electronics is the application of electronics for power conversion. A subcategory of power conversion is the AC to AC conversion.

There are two types of AC voltage controllers, single and three phase AC controller. They are used in practical circuits like light dimmer circuits, speed controls of induction motors and traction motor control etc. These configurations are the most used topologies due to their simplicity and use of fewer components.

Each has its advantages and drawbacks which determines the suitability for any specific application. The buck converter is a step-down, the boost a step-up while the buck-boost is both step-up and step-down. All these are non-isolated and use the inductor as the energy transfer element and are mostly used in board level power conversion and regulation. The isolated dc to dc converters use a transformer to provide the isolation, multiple outputs, a different voltage level, or polarity depending on the turns ratios and directions of the windings.

They are based on the non-isolated topologies but with the inclusion of a transformer. The commonly used types are, the full bridge, the half bridge, forward and the push pull converters, which are the isolated versions of the buck; and the flyback which is the isolated version of the buck-boost converter.

To improve performance, high frequencies and fast switching power semiconductor devices are used. The high frequencies increase the efficiency while reducing the physical sizes of the supplies since they allow the use of smaller components. The frequencies are usually above the audible range and in the range of between 20 KHz and KHz.