EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER By MUZAIDI BIN OTHMAN @ MARZUKI PPK SISTEM ELEKTRIK

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER Phase Angle Controller Resistive and Inductive loads PE curve Line current Harmonics TRIAC application

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER INTRODUCTION AC voltage controller is a converter that controls the voltage, current and average power delivered to an ac load from ac source. Electronic switches connect and disconnect the source and the load at regular interval. Common control method: Phase angle control Integral cycle control Tap changing control

The output voltage waveforms characteristic

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER APPLICATION Some of the application for phase angle control includes: The light-dimmer circuits Speed control of induction motor The input voltage is AC and the output is AC although it is not sinusoidal.

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER PHASE ANGLE CONTROL (R LOAD)

Using TRIAC

Gate pulse for T1, T2

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER = EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER PHASE ANGLE CONTROL (R LOAD) The output rms voltage is given by The output rms current The SCR rms current

OUTPUT VOLTAGE VS DELAY ANGLE, α (R LOAD)

HARMONIC AMPLITUDE VS DELAY ANGLE, α (R LOAD) Since the source and load current is non-sinusoidal, harmonic distortion is a consideration when designing and applying AC voltage controllers. Only odd harmonics exist in the line current because the waveform has half-wave symmetry. Normalized harmonic content of the line currents vs α is shown in Fig

EET307 POWER ELECTRONIC I AC –DC CONVERTERS EXAMPLE 1 The single phase AC Voltage Controller as shown below has a 120 Vrms 60Hz source. The load resistance is 15Ω. Determine: (a)The delay angle α required to deliver 500W to the load (b)The rms source current. (c)The rms and average currents in SCRs (d)The power factor (e)The total harmonic distortion (THD) of the source.

Solution (a) The required rms voltage to deliver 500 W to a 15 Ω -load is: By using equation:

Solution (a) Which yield:

Solution (b)(c)(d) (b) Source rms current is (c) SCR currents are determined from: (d) The power factor is

Solution (e) (e) Base rms current is

PHASE ANGLE CONTROL (RL LOAD) Figure (a) Single-phase AC voltage controller with an RL load; (b) Typical waveforms.

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER = EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER PHASE ANGLE CONTROL (RL LOAD) The load current in each half cycle is the same as for a controlled half-wave rectifier The output rms current

EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER = EET307 POWER ELECTRONIC I AC VOLTAGE CONTROLLER PHASE ANGLE CONTROL (RL LOAD)