Many years I have beaten head against wall when need to see at H-bridge simultaneously the both lower keys voltages and currents, and on gates and the same on high voltage keys. Now somehow one Project gave an unspent funding thus we decided to buy three identical osciloscopes. One control low voltage side, other high voltage side thus we may stand without of optocoupler probes. They are not extreme superior, but still 1 GSps and 100 MHz with 10 points thus most of all H-bridges are many orders beyound, and price was just laughful, 500 Eur. Name Siglenet SDS1000XE. Only thing I regret we hadnt bought four such instead of three.

 

I don’t understand. If the problem is that the inputs must be isolated from each other, how does using 3 scopes help (unless they run off separate isolation transformers)

 

Of course the isolation transformers are mandatory. And common synchro pulse is needed as well (what mostly may be a grid) or use the optosync.

To help realize the problem - H-bridge have upper side 538*2=1100 Volts distant from lower side. And signal levels are V(g)=-2...+40 V; V(d)=-538...+538 V, V(i(c))=0.1...1 V. Upper side the same but plus 538 ramp.

The tasks essencial to do - do the phase shift between both sides is large enough to make a 10 000 Amp shot into grid. How well are adjusted the DRC circuit of spike protection. What happens when rapidly increase or decrease the power consumption. What happens if change the frequency. Do the gate resistor is adjusted well. Do the gate booster is strong enough. Do the transformer "zero crossing" addendum is adjusted well. And so on.

 

Okay.