Author Topic: Calculating Hard-Switching losses  (Read 1433 times)

Offline Phoenix

  • High Voltage Experimenter
  • **
  • Posts: 70
  • Karma: +1/-0
    • View Profile
Calculating Hard-Switching losses
« on: July 31, 2018, 05:37:45 PM »
Hello  :)

I would like to calculate the maximum frequency i can drive an IGBT-Brick within its thermal limitation. I am using SKM200GB128D Bricks.

I am calculating the losses for 180A Hardswitching and a frequency of 20kHz. I need to find out the turn on/off energy first using the datasheet.


And here is my question: When reading the energy of the chart, do i need to use the 180A of current or the change of current (dI/dt)? The change of current would only be around 22.6A/µs high for 180A at 20kHz, which would result in much lower turn on/off energies.

Greetings,
Phoenix


Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1236
  • Karma: +17/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: Calculating Hard-Switching losses
« Reply #1 on: July 31, 2018, 06:54:55 PM »
It is your peak current, that is how I calculated it for soft-switching here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

I guess you can use my example all the way through, just ignore the reduction factors for resonant switching that I use :)
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Phoenix

  • High Voltage Experimenter
  • **
  • Posts: 70
  • Karma: +1/-0
    • View Profile
Re: Calculating Hard-Switching losses
« Reply #2 on: July 31, 2018, 08:06:16 PM »
Thank you for your reply  :)

I have already followed your guide for the calculations but i am stuck at that point. In this application i am only switching  an inductive load, which results in a triangular waveform. The IGBT's always switch at the peaks of this waveform (180A). There is no resonance circuit, so the IGBT's always switch at full current. Because of that, i think i have to read the chart at 180A of current. But if i read the chart at the operating current, i can't keep up with the manufacturers claim of 220A at 20kHz with a junction temperature of 150°C and a case temperature of 80°C. Here are my calculations:


As you see i am only able to switch at a maximum frequency of 8.462kHz but according to the datasheet the bricks should be able to switch 20kHz at 220A.

Is there something wrong with my calculations?

Edit: I just tried something new and i think i have found the problem: A square wave has a RMS-Factor of 1, but a triangular wave only has a factor of 0,577. The maximum current rating in the datasheet is for DC, so there are no switching losses included. If i put in the numbers for 127A (220*0,577) into the equations, the result is 23,462 kHz and it should work for my inverter. Could this result be correct?

Greetings,
Phoenix
« Last Edit: July 31, 2018, 08:54:19 PM by Phoenix »

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1236
  • Karma: +17/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: Calculating Hard-Switching losses
« Reply #3 on: July 31, 2018, 09:24:55 PM »
I was just about to mention that, just like I had to reduce for soft-switching short pulses, as hard-switching is seen as a square wave, a triangle waveform would also have to use a reduction factor, but you already figured that out :)
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Phoenix

  • High Voltage Experimenter
  • **
  • Posts: 70
  • Karma: +1/-0
    • View Profile
Re: Calculating Hard-Switching losses
« Reply #4 on: July 31, 2018, 10:27:35 PM »
I have now used the reduction factor for my 180A which gives me about 104A RMS. I used the RMS value for the CE Voltage and in the calculation for the conduction losses. But i have not used it for the turn on/off energy, because the IGBT still has to switch the 180A peak.

According to my calculations, if the junction has a temperature of 125°C and the Case has a temperature of 50°C, i can run my Inverter up to 20,6kHz. I also converted the equation to tell me the temperature difference between junction and case, at 20kHz the difference would be 73°C. I could now use a circuit which cuts of the supply voltage to the inverter using a relay, when the case temperature reachs 57°C, so the junction would never get hotter than 130°C  :D

Greetings,
Phoenix
« Last Edit: July 31, 2018, 11:57:15 PM by Phoenix »

Offline rikkitikkitavi

  • High Voltage Enthusiast
  • *
  • Posts: 35
  • Karma: +1/-0
    • View Profile
Re: Calculating Hard-Switching losses
« Reply #5 on: August 17, 2018, 03:44:38 PM »
Just a thought, wouldnt average value instead of RMS be more accurate?

The loss is the integral of the current*voltage across the switching device during the switching event.
A man can not have to many variacs

Offline Phoenix

  • High Voltage Experimenter
  • **
  • Posts: 70
  • Karma: +1/-0
    • View Profile
Re: Calculating Hard-Switching losses
« Reply #6 on: August 17, 2018, 04:47:21 PM »
I only used the RMS Value for the calculation of the conduction losses during the ON-State.

For the losses during the switching event, i used the full 180A, because the IGBT's switch at the current maximum.

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 291
  • Karma: +9/-0
    • View Profile
Re: Calculating Hard-Switching losses
« Reply #7 on: August 18, 2018, 03:26:03 PM »
Conduction losses for an IGBT should probably be done with the average (mean) current rather than RMS - they behave more like a diode than a resistor in forward conduction. RMS is appropriate for MOSFETs though, and it probably won't make a lot of difference anyway.

High Voltage Forum

Re: Calculating Hard-Switching losses
« Reply #7 on: August 18, 2018, 03:26:03 PM »

 


* Recent Topics and Posts

post Power diodes "hockey Puck"
[Sell / Buy / Trade]
rikkitikkitavi
January 26, 2020, 10:13:38 PM
post Re: Mazilli ZVS Driver Modification Problems
[Transformer (Ferrite Core)]
davekni
January 26, 2020, 04:55:49 AM
post Re: GM tube hv transformer
[Detection, Counting and Measurements]
futurist
January 25, 2020, 11:01:24 AM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
T3sl4co1l
January 25, 2020, 06:44:21 AM
post Re: Mazilli ZVS Driver Modification Problems
[Transformer (Ferrite Core)]
T3sl4co1l
January 25, 2020, 06:37:47 AM
post Re: Mazilli ZVS Driver Modification Problems
[Transformer (Ferrite Core)]
Andrew321
January 25, 2020, 02:22:09 AM
post Re: GM tube hv transformer
[Detection, Counting and Measurements]
haversin
January 25, 2020, 01:15:21 AM
post Re: GM tube hv transformer
[Detection, Counting and Measurements]
klugesmith
January 24, 2020, 10:53:42 PM
post Re: WTB [EU]: Cellular Sector Antenna
[Sell / Buy / Trade]
Da_Stier
January 24, 2020, 10:52:48 PM
post Re: GM tube hv transformer
[Detection, Counting and Measurements]
haversin
January 24, 2020, 10:29:14 PM
post Re: Problems with my first DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
bozidar
January 24, 2020, 08:16:12 PM
post GM tube hv transformer
[Detection, Counting and Measurements]
AlexanderHun
January 24, 2020, 06:24:25 PM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
rikkitikkitavi
January 24, 2020, 05:17:01 PM
post Re: My 833A VTTC
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 24, 2020, 04:37:25 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
justin66
January 24, 2020, 04:15:41 PM
post Re: My 833A VTTC
[Vacuum Tube Tesla Coils (VTTC)]
Mads Barnkob
January 24, 2020, 01:15:46 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
January 24, 2020, 01:10:38 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
January 24, 2020, 12:39:01 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
justin66
January 24, 2020, 11:43:08 AM
post Re: My 833A VTTC
[Vacuum Tube Tesla Coils (VTTC)]
kilovolt
January 24, 2020, 11:10:55 AM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
kamelryttarn
January 24, 2020, 10:11:51 AM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
kilovolt
January 24, 2020, 09:03:52 AM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
January 23, 2020, 11:50:22 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
January 23, 2020, 11:42:56 PM
post Re: WTB [EU]: Cellular Sector Antenna
[Sell / Buy / Trade]
Mads Barnkob
January 23, 2020, 11:35:07 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
justin66
January 23, 2020, 11:15:12 PM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
MRMILSTAR
January 23, 2020, 10:42:22 PM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
T3sl4co1l
January 23, 2020, 10:03:17 PM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
kilovolt
January 23, 2020, 09:55:05 PM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
MRMILSTAR
January 23, 2020, 08:39:10 PM
post Re: Universal bus precharge & fan speed controller
[Dual Resonant Solid State Tesla coils (DRSSTC)]
acobaugh
January 23, 2020, 08:37:43 PM
post Re: simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
acobaugh
January 23, 2020, 08:16:02 PM
post simple confusion about UD2.7c LEDs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
justin66
January 23, 2020, 07:48:39 PM
post Re: Bipolar high voltage multiplier project - more than 70cm hot arc discharge
[Voltage Multipliers]
kilovolt
January 23, 2020, 05:07:46 PM
post Re: My 240kv voltage multiplier
[Voltage Multipliers]
kilovolt
January 23, 2020, 05:05:40 PM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
kilovolt
January 23, 2020, 05:01:27 PM
post WTB [EU]: Cellular Sector Antenna
[Sell / Buy / Trade]
Da_Stier
January 23, 2020, 04:34:34 PM
post Re: My X-Ray Machine
[X-ray]
Agent Smith
January 23, 2020, 03:47:06 PM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
rikkitikkitavi
January 23, 2020, 02:24:07 PM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
kamelryttarn
January 23, 2020, 01:29:01 PM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
rikkitikkitavi
January 23, 2020, 12:45:40 PM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
kamelryttarn
January 23, 2020, 11:38:18 AM
post Re: DIY SMAW welder (stick welding)
[Electronic Circuits]
rikkitikkitavi
January 23, 2020, 10:43:36 AM
post DIY SMAW welder (stick welding)
[Electronic Circuits]
kamelryttarn
January 23, 2020, 08:32:56 AM
post Re: Doorknob vs Ceramic Disk
[Voltage Multipliers]
davekni
January 23, 2020, 06:06:20 AM
post Re: Mazilli ZVS Driver Modification Problems
[Transformer (Ferrite Core)]
davekni
January 23, 2020, 05:57:18 AM
post Doorknob vs Ceramic Disk
[Voltage Multipliers]
Andrew321
January 23, 2020, 03:57:09 AM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
January 23, 2020, 12:33:44 AM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
T3sl4co1l
January 22, 2020, 11:45:26 PM
post Re: CT performance investigations (Pearson and DIY)
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
January 22, 2020, 11:30:26 PM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal