DESIGN OF A THREE PHASE CONTROLLED RECTIFIER FOR USE IN THE LABORATORY

Size: px

Start display at page:

Download "DESIGN OF A THREE PHASE CONTROLLED RECTIFIER FOR USE IN THE LABORATORY"

Alexander Doyle
6 years ago
Views:

1 DESIGN OF A THREE PHASE CONTROLLED RECTIFIER FOR USE IN THE LABORATORY PRESENTED BY: MWONGA BRIAN MATOLO F17/39946/2011 SUPERVISOR: Mr. S. L. OGABA EXAMINER: Mr. OMBURA PROJECT INDEX: 116

2 Objectives Theory design Flowchart Results Conclusion Recommendations Outline

3 Objectives To design a three phase controlled rectifier circuit to convert three phase 110V AC input voltage to DC output voltage to be used in the lab. To develop a hardware of three phase controlled rectifier using six SCRs and a digital firing circuit to control the output voltage.

4 Theory Rectification is the processes of converting AC to DC using different electrical components Types of rectifiers Half-wave rectifiers Full-wave rectifiers

5 Theory (Cont ) Subdivided also according to their inputs either single phase or three phase. Further subdivided into uncontrolled, semi- controlled and fully controlled rectifiers..

6 Theory (Cont )

7 Theory (Cont )

Theory (Cont ) uncontrolled rectifiers use diodes as the rectifying device providing output of half cycle of input ac supply and the output is constant voltage value

8 Theory (Cont ) uncontrolled rectifiers use diodes as the rectifying device providing output of half cycle of input ac supply and the output is constant voltage value controlled rectifiers use thyristors or silicon- (SCRs) devices to rectifier controlled- rectifiers providing an output voltage that can set at any constant voltage value

9 Theory (Cont ) Three phase Controlled Rectifiers Uses thyristors (SCRs) to convert AC to DC Thyristors have three terminals the trigger pulse is applied to the gate while the anode cathodee voltage is positive.

10 Theory (Cont ) Thyristors conducts if a trigger pulse is present in the gate terminal together with the forward bias. controlling the angle of conduction consequently controls the average value of the output voltage.

11 Theory (Cont ) fully-controlled three phase bridge circuit

12 Theory (Cont )

13 Theory (Cont )

14 Design It consists of a three phase transformer in star / delta connection, six thyristor bridge connected, load, CLC filter, synchronization circuits, the trigger control and isolation circuit. Block diagram of three phase fully controlled rectifier.

15 Design(cont )

16 Design(cont ) The input to be rectified is an A.C 110V,50Hz supplied using a three phase transformer connected in delta/ /star connection and a safety fuse of 13A

17 Design(cont ) Synchronization circuit/ Zero crossing detector circuits This circuits are used to detect the zero points of the three ac supply helping to trigger the SCRs in the correct sequence.

18 Design(cont ) Transformer purposes To step down voltage to a lower and safer value up to the 6 to 9 volts rms provides the galvanic isolation between mains and zero crossing detection circuitry

19 Design(cont ) The square-wave signal at the output of the ZCD has same frequency as the sine and then is used as interrupt to the MCU.

20 Design(cont ) Controlling voltage circuit Analog Voltage (0-5 V) is used for controlling the converter power

21 Design(cont )

22 Design(cont )

23 Design(cont )

24 Design(cont )

25 Design(cont ) the opto-isolator purpose is; Monitor high voltage Output voltage sampling for regulation System control micro for power ON/OFF Ground isolating

26 Design(cont ) The mcu atmega328p was used and the program used explained in the flowchart below.

27 flowchart

28 Flowchart

29 Results

30 Conclusion Three fully controlled rectifiers are very popular in many industrial applications particular in situations where power regeneration from dc side is essential.in this the rectifier implemented was for use in the lab and used proteus software for simulation purposes.

31 Recommendations Following are areas of future study which can be considered for further research work. Speed Control Of Motors Transmission of HVDC

Battery Charger Circuit Using SCR

Battery Charger Circuit Using SCR Introduction to SCR: SCR is abbreviation for Silicon Controlled Rectifier. SCR has three pins anode, cathode and gate as shown in the below figure. It is made up of there