Thyristor Controlled Cyclo Converter design with pic microcontroller

Thyristor Controlled Cyclo Converter Drive for Controlling Speed of Induction Motor. The thyristor controlled cyclo converter system is very sophisticated solution for controlling the speed of induction motors, especially for single or three phase ac motors. Ac motors are so much significant in our daily life because these motors have so many applications in domestic or industrial level such as these have been using in washing machine, vacuum cleaner and water pumps. These motors have a constant speed, so their speed control is so much difficult work. Similarly, the power electronics is also very important in this modern world. Different companies or peoples are working of on ac motor drives such as variable frequency driver (VFD) by using power electronics but these drives are so much costly and are not in the range of normal company or man. Here, we are going to be designed an especial thyristor controlled cyclo converter drive for driving the single-phase inductionmotor. Whose cost would be very low as compared the other motor drives. Through this thyristor controlled cyclo converter drive the motor speed could be controlled in three steps. This drive would be made with the help of microcontroller 18F152 belongs to pic family, single phase transformer, bridge rectifier, voltage regulator, optocouplers and semiconductor switches such as thyristors.

The Block Diagram of the Thyristor Controlled Cyclo Converter Drive for Controlling the Speed of Induction Motor

Figure 1 The Block Diagram of the Thyristor Controlled Cyclo Converter Drive for Controlling the Speed of Induction Motor

Components List Thyristor Controlled CycloConverter Drive for Controlling the Speed of Induction Motor

This thyristor controlled cyclo converter drive has following components,

Transformer: In this thyristor, controlled cyclo converter drive the transformer is used for step down the ac voltages and works on the principle of mutual induction, which is gained by wapda. Here this would be step down the 220 v ac into 12 v ac.

Bridge Rectifier:This cyclo converter drive consists of electronics components which are operated on dc voltages therefore the ac voltages are converted into dc through bridge rectifier. Which consists of four diodes and connected at the output of transformer.

Blocking Diodes: The blocking diodes is connected at the output of bridge rectifier for blocking the reverse polarity current.

Voltage Regulator: In this thyristor controlled cyclo converter drive the voltage regulator is used for regulator the dc voltages which comes from the bridge rectifier. It regulates the 12 v dc into 5 v dc and for this purposes the LM 7805 voltage regulator have been used here.

Microcontroller PIC 18F452: In this thyristor controlled cyclo converter drive the pic 18F452 microcontroller have been used for the intelligent control of this drive. This microcontroller controls the firing angle of the thyristor voltages for controlling the speed of motor in three steps. It is powered up with 5 v dc a and interfaced with the optocoupler. It is 40 pins microcontroller and programmed in c language with the help of mikro/c software.

Optocoupler: Optocoupler is a 6 pins integrated circuit IC which is used for triggering the thyristor gate and for the isolation between the microcontroller and output load. In this thyristor controlled cyclo converter drive 8 optocouplers are used for 8 thyristors and is interfaced with microcontroller.

Dual SCR Bridge: In this thyristor, controlled cyclo converter drive dual SCR bridge is used which consists of 8 thyristors, which are controlled individually by 8 optocouplers.

Selection Mode:In this drive the selection mode is basically the switch, which is used for the selection of frequency and this drive is designed for three frequency steps.

Motor:In this thyristor, controlled cyclo converter drive the single-phase ac motor is controlled through this drive. Which is basically the inductive load.

Working Principle of the Thyristor Controlled Cyclo Converter Drive for Controlling the Speed of Induction Motor

This thyristor controlled cyclo converter drive works on the principle of variable frequency drive, when the frequency is changed then the speed is also changed. Here, first we would be drive the single-phase induction motor at fundamental frequency which is 50 Hz, then at f/2 Hz and then f/3 Hz. At fundamental frequency, the motor runs at its full speed which could be checked by the tachometer, then it would be drive at f/2 then the motor runs at half speed and then motor is drive at f/3, at this frequency the motor speed could be quarter. This drive consists of two switches one for power on this drive and second one for frequency selection mode. When the frequency is changed by using the frequency selection mode switch then the microcontroller which is programmed accordingly to the frequency change mode gives the signal to the optocoupler. The optocoupler which is electrically isolated from the thyristor gives the trigging signal to the thyristor. The thyristor, which is directly coupled to the single-phase motor drive the motor as per signaling frequency. The microcontroller basically increase or decrease delay time of the trigging signal, which is inversely proportional to the speed of the single-phase motor. The delay time is set in microcontroller through programming.

Applications and Advantages of Thyristor Controlled Cyclo Converter Drive for Controlling the Speed of Induction Motor

1. This thyristor controlled cyclo converter drive can be used in industrial and domestic application such as the machine which have single-phase motor can be drive through this drive.
2. This thyristor controlled cyclo converter drive can be used in vacuum cleaner, washing machine and water pumps.
3. This drive can be used for controlling the speed of drill machine because some time we have required low speed and high torque for this purpose this is best drive.
4. This drive can also be used for the speed control of cement mill drives, Ship propulsion drives, rolling mill drives, Scherbius drives, Ore grinding mills and mine winders.
5. This thyristor controlled drive is less costly and efficient and compared to the other motor drives.