Help me understand the switching in UPS

[Gaber Mohamed Boraey]

Hello

In the UPS there is inverter for converting from DC voltage to ac

There are different types of UPS, for example, the line interactive UPS
This UPS generate modified sine wave output

other types of ups within capacities start at 2k, or 3k and higher , the output is sine wave

I work on repair daily
most of the problems i see, are in the IGBT or Mosfet burned due to higher loads at customer site or high temperature area where is the UPS installed
and sometimes I don't find the same part number, so i start the challenge of finding equivalent number within similar or higher characteristics of IGBT or Mosfet

I always worry about timing issue in the part i replace, afraid if two IGBT or 2 Mosfet open at the same time, and then there is a short circuit

we don't have schematics, only block diagram , and not for all , the machines are different, but the concept is same for ups ,
like in this photo

most of problems are in the inverter, and the inverters differ from machine to another based on the capacity of machine

what I need understand, or want understand, is when I replace IGBT with equivalent, the parameters for switching times, such as td on , td off, tr " rise time " , tf " fall time ", will not cause short circuit while the controller or pwm generator will have dead time between transients from on to off for IGBT's?, and this deadtime is big with comparison to timing for IGBT?, or still in ns? " nano seconds"

in simple words, do I have to worry about timing when change IGBT with equivalent?, for not cause short circuit?, I understand about losses and more heat dissipation if slower IGBT, but how
about on and off times?

can you explain to me how the switching work in inverter in UPS?
thanks

 

[aliarifat794]

Slower IGBTs/MOSFETs will result in higher switching losses, generating more heat.

 

[ILIA KALISTRU]

940-435-0242

Slower IGBTs/MOSFETs will result in higher switching losses, generating more heat.

My understanding is that OP is more concerned with Shoot-Through current in push-pull when the replacement transistor in one leg closes slower than the remaining original transistor in the other leg opens. Or when the replacement transistor opens earlier than the original transistor closes in the other leg.

While not an expert in this topic, I would think about changing both transistors to matching faster devices. (take my advise with a shovel of salt)