Al-Najah National University Electrical Engineering Department Speed Drive For Three-Phase Induction Motor Presentation By Eng.Mu’taz S. Al-Sheikh & Eng.Khalid Hammoudeh Supervisor Prof . Dr . Marwan Mahmmod

Methods for drive speed of IM : Nsyn = 120 f / P Changing number of poles (P) : This method requires a motor with special stator winding Changing line frequency (f) : Changing in (f) is affect in magnetization current & flux Ф α 1/f Changing line voltage (v): Changing in (v) is affect in magnetization current & flux Ф α v

Methods for drive speed of IM : The perfect method for drive is : Changing line voltage proportional to frequency The ratio V / f constant. The advantages of this method clearly in: The flux (Ф) remains constant. The torque remains constant at any speed under the rated speed. Note that : this project use the fourth method for controlling under rated speed.

Methods for drive speed of IM : Characteristic curve for V/f constant :

Voltage source inverter (VSI) : The general categories of (VSI) inverter: Square wave inverter : The DC voltage Is controlled in order to control the magnitude of the AC output voltage and the inverter control the frequency. The output voltage is a square wave voltage.

Voltage source inverter (VSI) : Pulse width modulation inverter (PWM) : The DC voltage Is constant and the inverter control the magnitude of the AC output voltage and the frequency. The behavior of one leg inverter. To obtain any desired frequency , a sinusoidal control signal at desired frequency compared with a triangle wave . Vcont > Vtri T+ IS ON Vcont < Vtri T- IS ON

The control wave & output wave form for three leg (PWM):

Three-phase pulse width modulation : It is contain from three leg inverter . Full power circuit for three phase IM drive .

PWM generation chip (HEF-4752V) PIN CONFIGURATION FOR THE CHIP :

Information of the pins : Pin 8 : drive signal for upper switching device for R-phase Pin 9 : drive signal for lower switching device for R-phase Pin 22 : drive signal for upper switching device for S-phase Pin 21 : drive signal for lower switching device for S-phase Pin 3 : drive signal for upper switching device for T-phase Pin 2 : drive signal for lower switching device for T-phase Pin 25: for determine the drive signal are in thyristor or transistor mode Pin 24 : stop /start signal Pin 7 : for the delay time Pin 5 : for the reversing direction

Information of pins Pin 12 : to control the inverter output frequency (f p12 = 3360*f0) Pin 17 : control the output voltage of inverter Pin 4 : setting for inverter switching frequency

PWM Inverter (sequence of operation) : Project Block Diagram :

Control Circuit of Project :

Setting for Data Input : 1. fFCT = 100 - 220 KHz ( results in varying output frequency from 30 to 85 Hz ) 2. fVCT = 300 KHz (results in obtaining V/f constant up to f01 =50 Hz). 3. fOCT = 560KHZ (results in delay between the upper and lower transistor operation = 0.0285 ms ). 4. fRCT = 560KHz (results in the maximum switching frequency = 2KHz )

Isolator & Driver Circuit :

The Results : The minimum output frequency set to be 30Hz and the wave form of VRY is shown in fig The maximum output frequency set to be 85Hz and the wave form of VRY is shown in fig.

The Results : The 120˚ phase shift between R,Y phases :

Inverter Use in Project :

Measurements : Voltage V / F ratio 30 35 40 50 50-85 V / F = Constant , Showing in the table below Frequency Voltage V / F ratio 30 14 0.47 35 16 0.46 40 19 0.47 50 20 0.4 50-85 20 ……

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