Types of Step Up Cycloconverters
The Two Types of SCyclo Conveters are Given Below
- Mid Point Step Up Cycloconverter
- Bridge Type Step Up Cycloconverter
Mid Point Step Up Cycloconverter
It consists of a single -phase transformer with mid tap on the secondary winding and four thyristors . Two of these thyristors P1, P2 are for positive group and the other two N1, N2 are for the negative group. Load is connected between secondary winding mid point ‘o’ and terminal A as shown . During the positive half cycle of supply voltage of terminal a is positive with respect to terminal b. Therefore , in this positive half cycle both SCRs P1 and N2 are forward biased from ωt = 0 to π . When SCR P1 is turned on at ωt = 0 then the load voltage is positive with terminal A positive and terminal o negative. The load voltage now follows the positive envelope of the supply voltage . At instant ωt1 , P1 is force commutated and forward biased thyristor N2 is turned on so that load voltage is negative with terminal o positive and terminal A negative . The load , or output voltage now traces the negative envelope of the supply voltage.
Cycloconverter Circuit
At instant ωt2 , N2 is force commutated and forward biased thyristor P1 is turned on so that load voltage is positive and follows the positive envelope of supply voltage. After ωt = π terminal b is positive with respect to terminal a ; both SCRs P2 and N1 are therefore forward biased from ωt = π to 2 π . At ωt = π , N1 is force commutated and forward biased SCR P2 is turned on. In this manner , SCRs P1 and N2 for first half cycle ; P2 and N1 for second half cycle and so on are switched alternatively between positive and negative envelopes at a high frequency . As a result output frequency f0 , is higher than the supply frequency fs as shown with f0 = 6fs .
Mid Point Step Up Cycloconverter Waveform
Bridge Type Step Up Cycloconverter
It consists of a total of eight thyristors , P1 to P4 i.e. four for positive group and the remaining four for the negative group N1 to N4. When a is positive with respect to x i.e. during the positive half cycle of supply voltage pairs P1 , P2 and N1, N2 are forward biased from ωt = 0 to π . When forward biased thyristors P1 , P2 are turned on together at ωt = 0 , the load voltage is positive with respect to x , so that load voltage is positive with terminal A positive with respect to o . Load voltage now traverses the positive envelope of supply voltage .
Bridge Type Step Up Cycloconverter Circuit
At ωt1 , SCRs P1 and P2 are force commutated and forward biased pair N1 , N2 are turned on. With this , load voltage is negative with terminal o positive with respect to A. Load voltage now follows the negative envelope of source voltage. At ωt2 , N1 and N2 are force commutated and P1 and P2 are turned on. The load voltage is now positive and follows the positive envelope of source voltage. After ωt = π , thyristor pairs P3 , P4 and N3 , N4 are forward biased , these can therefore be turned on and force commutated from ωt = π to 2 π . In this manner, a high frequency turning on and force commutation of pairs P1 P2 , N1 N2 and pairs P3 P4 , N3 N4 gives a carrier frequency modulated output voltage across load terminals .
Bridge Type Step Up Cycloconverter Waveform
Cycloconverters
Cycloconverters are power electronic devices designed to convert electric power directly from one frequency to another, typically without the need for an intermediate DC link. Additionally, they are employed in specialized systems where precise control of output frequency and low harmonic distortion are crucial. However, challenges include complexity in control strategies and the presence of harmonics in the output waveform, requiring careful design and control for optimal performance. A cycloconverter is thus a one-stage frequency changer. The fundamental principle of a cycloconverter involves breaking down the input AC power into smaller segments and reassembling them to form the desired output frequency.
In this Article, We will be going through Cycloconverter in power electronics, We will go through what is a Cycloconverter, its Type with its Construction, and its Characteristics, At last, we will conclude our Article with Some Solved Examples and FAQs.
Table of Content
- Cycloconverter
- Types
- Construction and Components
- Characteristics
- Advantages
- Disadvantages
- Applications
- Solved Example