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Thanks
,
and others for help.
Found the problem. I'm not commutating, just switching the DC positive ON and OFF. I mean;
when gate signal high Load = Vdc
when gate signal low Load = Nothing, open circuit.
Assuming there is a little inductance on rheostat, overshoot is not abnormal. I guess I...
I've removed the blue channel, measuring the yellow only. Result is still the same. Still there is a big overshoot.
Soon I'm going to add a 4700uF 63V capacitor to output rail and test it again.
I used metal screws so there is electrical conduction. I tested short circuits with middle pin and yes they are electrically connected. I'm not sure if it is the problem. I think I should get a differential probe to clear the risks.
Probe connector is a simple BNC connector. There is no screw. I borrowed probes from a friend and yes they had a screw to calibrate. I calibrated the proble with test signal on oscilloscope. Nice sharp squares.
=Probe calibration check
=Using shielded short cables for gate driver source check...
I have been suspecting why there is a little screwdriver in probe packs. Now it's clear =) I'm heading to my workshop. Thanks a lot.
Update : There is screwdriver but no screw =( Rest of the probe is a whole piece that I can't apart.
Rheostat is a simple one, 100ohm total, 250Watt. Snubber is not an option at this point. If those overshoots are not a measurement error, I'll try varistor to oppress/suppress (I couldn't decide which one is suitable) or try a clamp like below.
I really don't believe that our cheap probes...
Yes they are different grounds, It is just ment to observe overall. Trigger is on CH1 and it's on the load which I want to observe best. Disconnecting blue signal doesn't effect yellow. Still same.
What is your suggestion about this issue ?
I'm more worried about the slope between rise and...
15V supply enclosures are metal and well earthed. I have to use long cables for first prototype. Do you advice me to use twisted pair cables ? Shielded cables ? Ferrite Choker ?
Oscilloscope earthing is isolated. Another terms, oscilloscope has no earthing for some reasons.
This slope...
Thanks for reply mate. Going down the list one-by-one. Sorry if sometimes I look rude, it is unintentional and caused by my lack of english skills.
It is not an DC-AC inverter, it is an AC-AC converter. IGBT's connected the way how a bidirectional switch operates. The PCB is (3Pin 1Pout) only 1...
Hello,
I'm trying to build a 3phase-3phase direct converter (Explains my schematics). I'm testing IGBT stage with DC source. Circuit is now just triggering IGBT named SAAF.
Cutting to the chase, I'm triggering only 1 IGBT and chopping a DC for now. I'm sure there will be negative undershoot if...
That's basically putting a capacitor at source.
Do you mean there will be an energy stored in PCB because of an stray inductance and bypass it via that capacitor ? What if the input is AC not DC ?
- - - Updated - - -
I searched many manufacturer IGBT tutorials, application notes, datasheets...
I've been searching for decoupling caps for IGBT like 1 hour a day like 2-3 days. I checked many tutorials, datasheets and application notes. I haven't seen any decoupling capacitors.
What is the "decoupling capacitor" in IGBT commutating / driving ? Do you mean to putting a capacitor between...
Minimum capacitance formulas for DCDC
C= (Vout(peak) x DutyCycle% x Switching Period) / (Vripple x Rload)
or
C= (Duty Cycle x Imax ) / (Vripple x switching frequency)
The voltage rating of capacitor must be smallar than 2 times of input voltage.
since so far both worked for me.
For...
Vcm is for both inputs. It pushes the signal from both sides.
Speaking regardless of the input/output demans of picture I shared; Is this what I should understood ?
We have an input signal Vi(t)=2.cos(wt)
Vcm set to 2V and Vcc=5V, gain set to 1
Output is now Vo(t)=Vi(t)+2
Signal should swing...
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