Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Inverter Welding DC-DC Converter: Transformer Saturation

Status
Not open for further replies.

memarian

Full Member level 5
Joined
Aug 11, 2004
Messages
257
Helped
57
Reputation
114
Reaction score
34
Trophy points
1,308
Activity points
2,005
Hello,

I'm building a prototype 37V-350A inverter welding machine. Currently i'm using Full bridge topology and hard switching (with 2 PWM control signals, one for LEG A, One for LEG B). Rectified 3 phase AC is connected as main input voltage. Switching frequency is 31250 Hz. (32 us period). my Main controller is an ARM processor that produce PWM signal and i'm using a driver circuit to drive 1200V-75A IGBTs. my main transformer has a special Core ,which according to the manufacturer is specially designed for welding machines upto 500A.
(transformer turn ration : N1=21 N2=3) i'm using a special HIGH Voltage-LOW ESR Capacitor in series with main transformer for Possible DC-Blocking.

The machine works fine and without any problem up 190A OUTPUT. when i started to use the machine at higher output currents ,the Over current protection triggered. After Investigating the CT ( current Transformer) outputs i noticed some spikes on one of the PWM Pulses which means that main transformer has been saturated. I tried the test several times and each times it randomly saturated on one the PWM Signals only.( in some tests on signal for LEG A, in some tests on SIGNAL for LEG B but this happen above 190A)

After investigating PWM signals , i see both legs are ok and pwm signal are matched and there is no unbalance between PWM pulses(resolution = 10ns).Also there is enough dead time between both PWM Signals ( PWM duty cycle is barely over 50% Duty Cycle!).

Currently i don't know this this happens above 190A.Any ideas?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top