AC Voltage Controller.pptx

ac voltage controller

1. AC Voltage Controllers

2. If a semiconductor switch is connected between ac supply and load, the power flow can be controlled by varying the rms value of ac voltage applied to the load; and this type of power circuit is known as ac voltage controller. AC Voltage Controllers

3. AC Voltage Controllers Single-phase controllers Bidirectional or Full-wave control Unidirectional or Half-wave control Bidirectional or Full-wave control Unidirectional or Half-wave control Three-phase controllers

4. AC Voltage Controllers For power transfer in an AC converters, following types of control methods are used: Phase angle control On-Off control (Extinction angle control) or Integral cycle control or burst firing control PWM control 4

5. Principle of Phase Control 5

6. Principle of On-Off Control (Integral cycle control)

7. The basic principle of on-off control technique is explained with reference to a single phase full wave ac voltage controller circuit shown below. The thyristor switches T1and T2 are turned on by applying appropriate gate trigger pulses to connect the input ac supply to the load for ‘n’ number of input cycles during the time interval Ton. The thyristor switches T1 and T2 are turned off by blocking the gate trigger pulses for ‘m’ number of input cycles during the time interval Toff . The ac controller ON time Ton usually consists of an integral number of input cycles.

8. (a) Power-circuit diagram (b) voltage and current waveforms Single-phase unidirectional ac voltage controller

9. Single-phase Bidirectional full wave ac voltage controller using two anti-parallel thyristors

10. Single phase Bi-directional full wave ac voltage converter using TRIAC

11. Single phase full wave ac converter with common cathode configuration

12. Single Phase Full Wave AC Voltage Converter Using a Single Thyristor

13. Three-phase Full-Controlled AC Controller

14. APPLICATIONS OF AC-AC CONVERTERS The most common applications of AC-AC converters are: Industrial heating and domestic heating On-load transformer connection changing Light controls Speed control of poly phase Induction Motors AC magnet controls Air-craft Household appliances Electronic ballasts. 14

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