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PWM WAVEFORM GENERATION USED IN THE TEST SYSTEM

        

DUTY CYCLE & GROUNDED PHASE CONDITIONING After normalizing and setting the gain factor of the above equation set, the duty cycle for each point of the wave form is ready to be calculated digitally. A physical number is generated representing the number of counts for each of the phases the high FETs should be ON based on the physical point of the waveform. Since this is an H Bridge configuration, the lower FET would be ON the remaining of the duty cycle for the selected point in the period. A a dead time is also required between switching the upper FET ON and lower FET ON. The IF-THEN condition shows the relationship to the actual voltage from the equation set to the FET-ON duration for each phase.  This number DCxh, DCxl  is then incorporated into the BYTE table and hence the PWM wave form is generated for the three phases. The GROUNDED PHASE Technique is taking the output amplitudes generated by the equation set and normalizing it to the phase that has the lowest amplitude. The graph below is the actual wave form table generated by the application program for a 45 %  Duty Cycle.  The CASE statements to generate this waveform from a Sinewave PWM is shown on the left. The waveform shown below is a grounded phase PWM sinewave plus a 3rd harmonic content. This is explained in the PMB motor analysis section.

DUTY  CYCLE  ALGORITHM  FOR  EACH  PHASE The duty cycle of each phase is referenced to the actual amplitude for the phase equations and then calculated to fit the number of points in the period. The default value is 1000 points per PWM period per waveform point. The default playback clock rate is 25.00MHz, 50 nanoseconds. This defaults to a 13 millisecond sine wave period for 260,000 byte playback memory size, (1000 pulses per vertical resolution per point • 260 points per period). This allows for a 0.1% default duty cycle resolution per waveform point.  The number of points for the PWM period is programmable as well as the number of points for the waveform period. IF Va = 0 THEN         DCah = 0         DCal = INT(PERIOD) ELSE         DCah = ABS(INT((Vab(PT) * PERIOD * DtyCyc) + .5))         DCal = INT(PERIOD - DCah) END IF IF Vb = 0 THEN         DCbh = 0         DCbl = INT(PERIOD) ELSE         DCbh = ABS(INT((Vbc(PT) * PERIOD * DtyCyc) + .5))         DCbl = INT(PERIOD - DCbh) END IF IF Vc = 0 THEN         DCch = 0         DCcl = INT(PERIOD) ELSE         DCch = ABS(INT((Vca(PT) * PERIOD * DtyCyc) + .5))         DCcl = INT(PERIOD - DCch) END IF

GROUNDED PHASE ALGORITHM  FOR  EACH  PHASE SELECT CASE Vab       CASE IS > Vbc           ' Vca & Vbc = 0 test           IF Vbc > Vca THEN                 Vgnd = Vca                 Vc = 0                    Vab = Vab - Vgnd                 Vbc = Vbc - Vgnd           ELSE                 Vgnd = Vbc                 Vbc = 0                 Vab = Vab - Vgnd                 Vca = Vca - Vgnd           END IF     CASE IS > Vca                   ' Vbc & Vca = 0 test           IF Vbc < Vca THEN                 Vgnd = Vbc                 Vbc = 0                 Vab = Vab - Vgnd                 Vca = Vca - Vgnd           ELSE                 Vgnd = Vca                 Vca = 0                 Vab = Vab - Vgnd                 Vbc = Vbc - Vgnd           END IF     CASE ELSE               ' Vab = 0  test                 Vgnd = Vab                 Vab = 0                 Vbc = Vbc - Vgnd                 Vca = Vca - Vgnd END SELECT

Sine Grounded Phase MathCAD Generated 3Ø  Equation set

Triplen Grounded Phase MathCAD Generated 3Ø Equation set after Gain and Offset are applied

        

Sine Grounded Phase BRIDGE DRIVE Test Program PWM Data Table

Triplen Grounded Phase BRIDGE DRIVE Test Program PWM Data Table generated from the program

Sine Grounded Phase BRIDGE DRIVE ON/OFF TIMES MathCAD Generated Analysis from Data Table

TRIPLEN Grounded Phase BRIDGE DRIVE ON/OFF TIMES MathCAD Generated Analysis from Data Table

        

0 TO 100 amps rms Phase Current 26 Milli-ohm 40µh Phase to Phase Load Empirical Data Table, Phase Current = phase x 20 amps

0 TO 100 amps rms Phase Current 26 Milli-ohm 40µh Phase to Phase Load Delta and WYE Load configuration Phase to Phase DC Resistance in milli-ohms at 40µh A - B             B - C            C - A 26.22            26.26            26.54

        

Empirical data, 0 TO 100 AMP rms  3 Ø  Current into a  Delta configuration,   26 Milli-ohm 40µh Phase to Phase Load,  Phases A, B & C  Balanced Output Graph

90 AMP rms 3Ø Current into the  Delta Load Configuration,  26 Milli-ohm 40µh Phase to Phase Load of Empirical data

Comparison of the Sine and Sine + 3rd Harmonic additive Phase Current vs Supply Current of Empirical data

        

THERMAL DISTRIBUTION OF THE MOUNTING MECHANISM FOR A CERAMIC SUBSTRATE, PHASE A OF THE POWER MODULE WITH 60 AMPS RMS TO THE LOAD, 36 SECONDS ON, 180 SECONDS OFF DUTY CYCLE FOR A 50 MINUTE TEST PERIOD

ONE CYCLE 30 MINUTES INTO THE RUN, THERMAL DISTRIBUTION OF THE MOUNTING MECHANISM FOR A CERAMIC SUBSTRATE, PHASE A OF THE POWER MODULE WITH 60 AMPS RMS TO THE LOAD, 36 SECONDS ON, 180 SECONDS OFF DUTY CYCLE FOR A 50 MINUTE TEST PERIOD

        

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