On the diagram above there are 2 connections labeled +HVDC and -HVDC, please can anyone explain this cos it gets me very confused. Is this the amplified voltage from the IGBT?, Ive seen IGBT's in inverters but I noticed that there is always a step up transformer somewhere. I thought IGBT's are just fast switches. If I am supposed to connect power to this part of the circuit, how much should that be because from the look of the diagram, whatever is connected to these points will find its way to the low DC section via Q1. Thanks for reading.

 

Those are the connections from the power supply.
Read up on H Bridge circuits. Q1 and Q2 are never turned on at the same time. The same goes for the other pairs of transistors.

 

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On the diagram above there are 2 connections labeled +HVDC and -HVDC, please can anyone explain this cos it gets me very confused. Is this the amplified voltage from the IGBT?, Ive seen IGBT's in inverters but I noticed that there is always a step up transformer somewhere. I thought IGBT's are just fast switches. If I am supposed to connect power to this part of the circuit, how much should that be because from the look of the diagram, whatever is connected to these points will find its way to the low DC section via Q1. Thanks for reading.

IGBTs aren't THAT fast - they're basically a hybrid Sziklai pair, which amounts to a speed limiting emitter follower output.

I replaced no end of IGBTs in monitor PSUs with regular MOSFETs - designers were pushing switching speed for smaller cheaper reactive components. Some of them just couldn't grasp that IGBTs aren't fast enough to do that.

 

IGBTs aren't THAT fast - they're basically a hybrid Sziklai pair, which amounts to a speed limiting emitter follower output.

I replaced no end of IGBTs in monitor PSUs with regular MOSFETs - designers were pushing switching speed for smaller cheaper reactive components. Some of them just couldn't grasp that IGBTs aren't fast enough to do that.

Thanks Ian, I been trying to run a brushless motor I took out of a washing machine, Ive invested quite a bit on this project but its beginning to look like its not going to get of the ground. I cant get all the info needed, even the pc that Im going to use to drive it may not be fast enough cos Im using Qbasic but it looks like I will need assembler. The workload is a lot and Im learning new things everyday that makes the project harder.

 

Thanks Ian, I been trying to run a brushless motor I took out of a washing machine, Ive invested quite a bit on this project but its beginning to look like its not going to get of the ground. I cant get all the info needed, even the pc that Im going to use to drive it may not be fast enough cos Im using Qbasic but it looks like I will need assembler. The workload is a lot and Im learning new things everyday that makes the project harder.

IGBT are probably OK to about 10 - 15Khs, Modern MOSFETs have competitive RDSon figures and can go faster.

 

Hello,

Have a look at the attched PDF for the difference and applications of mosfet and igbt.

Bertus