Presentation. The convertors in dc drive systems are designed to control and supply separately-excited dc machines in applications that demand rapid response, high accuracy and great reliability.
Single converters. In a single convertor the thyristors are arranged in a six-pulse two-way circuit (see Fig. 1,a).
The convertors are available with single-convertor arrangement and in double-convertor arrangement.
Single converters. In a single convertor the thyristors are arranged in a six-pulse two-way circuit (see Fig. 1,a).
Fig. 1:
a - single convertor; b - double convertor
A single convertor can supply current in one direction only, but its output voltage can change polarity. This determines the rotation and torque direction characteristics of the machine, as illustrated in Fig. 1,a.
The single convertor can operate in the first and fourth quadrants. The direction of torque can only be changed by reversing the field current of the machine.
Double convertors. In a double convertor there are two sets of thyristors connected in antiparallel (see Fig. 1,b). Both current and voltage can change sign, and the machine can be braked and reversed without additional equipment; this is known as four-quadrant drive.
Converters (also spelled "convertors") are devices that change electrical energy from one form to another. They are crucial in various applications to ensure that electrical energy can be used efficiently and safely. Here are the main types of converters:
AC to DC Converters (Rectifiers):
- Function: Convert alternating current (AC) to direct current (DC).
- Applications: Used in power supplies for electronic devices, battery charging, and DC motor drives.
- Types: Half-wave rectifiers, full-wave rectifiers, and bridge rectifiers.
DC to AC Converters (Inverters):
- Function: Convert direct current (DC) to alternating current (AC).
- Applications: Used in uninterruptible power supplies (UPS), renewable energy systems (such as solar power), and AC motor drives.
- Types: Square wave inverters, modified sine wave inverters, and pure sine wave inverters.
DC to DC Converters:
- Function: Change the level of DC voltage from one value to another.
- Applications: Used in battery-operated devices, power supplies for portable electronics, and electric vehicles.
- Types: Buck converters (step-down), boost converters (step-up), buck-boost converters, and flyback converters.
AC to AC Converters:
- Function: Change the level of AC voltage or frequency.
- Applications: Used in variable frequency drives for AC motors, voltage regulation, and power conditioning.
- Types: Cycloconverters and matrix converters.
Each type of converter serves a specific purpose and employs different technologies to achieve the desired conversion. For instance:
- Rectifiers use diodes and sometimes capacitors to smooth out the converted DC signal.
- Inverters use switching elements like transistors or thyristors to generate AC from DC.
- DC-DC converters use inductors, capacitors, and switches to efficiently change the voltage level.
- AC-AC converters may use semiconductor devices to directly alter the AC waveform or frequency.
Converters are essential in modern electronics and electrical systems, enabling the efficient and flexible use of electrical power across a wide range of applications.
