Transformer Operating Frequency = 25.6Khz T=39uSec

Sine output is constructed from 256 varying width pulses per half cycle of output, 
ie 50hz* 512 = 25.6khz pulse rate. To prevent flux walking problems in the push pull
transformer circuit each side is driven alternatly with equal width pulses. The half sine
outputs are multiplexed back as a full sine wave and then filtered.

Because the modulated pulses don't reach 100% maximum width, allowance for this 
means the primary voltage is reduced to about 0.9 of maximum possible. The high
frequency greatly reduces the core size and winding quantity of the heavy gauge 
primary needed to carry the current. 


Sec power = 1500watts				Pri Power = 1500/98% = 1530 watts
Sec volts = 240 v rms					    Pri volts = 48*0.9 = 43.2
Sec current = 6.25 amps rms				Pri current = 1530/43.2 = 35 amps

   Txfr	Area Product    = Core area.Winding area 		   (cm^4)
			= {Power/(K *delt B(Tesla) * freq(Hz)}^4/3 (cm^4)	     K=0.015
										     F=25600
			= {1530/(0.015 * 0.7 * 25600} ^ 1.333			     B=2*.35
			= {1530/268.8} ^ 1.33
			= 10.1 (cm^4) 

	Epcos E55  core csa = 3.57 sq cm.for 1.7 cm * 2.1 cm or csa 0.000357(m^2)
	      E55  Winding csa = 1.9 sq cm Product = 7cm^4

		   	
	Turns/volt =          1
		     __________________________________		mks units	
		     Root (Pi* B max * core csa * freq)		core csa = sq metres,
								B = webers/sq metre(Teslers)
								F = Freq (Hz) K = 1 core stack 		
		
		   =          1
		     ____________________________
		       root (pi*0.35*.000357*25600)	 
		  
		 =    0.31 TPV

		
Pri Turns = 48v*.315 = 15.12 (15) turns per side, Bifilar wound.

Sec Turns ratio Vo/Vi = 240*1.414(Peak)+ diode drops=1v)/43.2 * 15.12 = 119 turns.
Allowing for txfr efficiency, say 95% brings the turns to 119/.95 = 125 turns per side.

Winding Wire Gauges:
Let copper losses = 10 watts primary + 10 watts secondary = I^2 R then 
	Res Secondary = 10/6.25*6.25 = 0.25 ohms maximum.
	Power is divided by centre tapped windings which allows 0.5 ohm/winding
	
	Sec mean diameter = 30mm.  Metres/ohm = pi*30*126turns/0.5= 23 mets/ohm
	Sec wire diameter = 0.71mm or 22 swg.
	
	Res Primary = 10/22*22 = 0.02 ohms
	Res Primary = 10/35*35 = 0.008 ohms
	Power is divided by centre tapped windings which allows 0.016 ohm/winding
	
	Pri Mean dia = 27mm. Mets/ohm = pi*27*15 turns/.016  =  79 mets/ohm 
	Pri wire diameter = 1.2mm =  18 swg (16 better)

Switching pulse widths (F=25600hz):
Maximum = 39.06 usec * 90% = 35.15usec
Minimum = 35.15 usec * 1/128 = 0.274 usec = 274ns (128 pulses for 90 degrees 
sine wave) 

Switching Transistors:
Primary side must be able to stand off 2* 48 plus a healthy margin.
FQP32N20C, 200v, 30Amp cont, tr & tf ~20 nsecs 
Switching losses = 3 watts. Channel on losses = (38 mv* 8 amps)say 600 at 20 = 12watts. 
Total 15 watts each driver.

Secondary side must be able to stand off 640 v plus margin.
Fairchild FQ8N100C will block 1000v and pass 8A cont 30A pulsed, Rds = 1.4 ohm at 4A
Rectifiers: MUR8100E are 1kv working

Transformer Core:
Ferrite core set at Farnell Epcos E55  B66335GX127 @ £3.06 for half 
core *2. Former = £2.21. 
Transformer wire (18swg 1.2mm at Maplins = £6.9)