gating signal for six MOSFETS or SCRS

[grmahun]

I want to design a three- phase, 380V,50Hz  inverter from a battrey of  12 - 24V  dc source. This needs six pulse gating signal for the six  SCRs or MOSFETs.
Could you please help me with the design of these gating signals.
TQ in advance.

 

[ante1]

Hi,

What are the expected output ratings?

 

[indulis]

I think the more interesting question is how to phase shift each of the gate pulses 120 degrees for each phase!!

 

[ante1]

Hi,

I think you should look at an IGBT inverter bridge for this. Perhaps it is possible with mosfets too but common thyristors should be avoided I believe. This can be controlled by a 12-puls system, much like the second half of a 3-phase motor AC-drive. It will not produce perfect sine wave but close enough. If you need high output power then 12 and 24 Volts system should be avoided, the currents will be troublesome to control.

 

[grmahun]

The expected output ratings : 3kw,380v(L-L),50HZ
  The phase shift 120 degree including dead time generation between
the gating signals of mosfets in one leg.
  There is no need of to get perfect sine wave it can be square wave because this inverter is used to drive 3 phase induction motor.
  I think IGBT could be better as posted by Ante but we have only accese to mosfet in our lab.The DC could also go up to 48V.

 

[ante1]

Even at 48 Volts you still have to deal with about 70 – 80 A at 3000 W output!

 

[grmahun]

Does that mean there is no alternative to drive  a 3 phase induction motor 
from car battery or solar source for at least power output of 1hp.

 

[ante1]

A regular size car battery will not run a 1hp output motor for more than a few minutes. The battery will be destroyed after only a few cycles (charge/discharge) since a starter battery is not suitable for deep cycle use (deep discharge). 

 

[grmahun]

Thanks Ante,I think the source from the battery makes the design
more difficult than I thought.How about if the source is from mains using step down transformer and rectified to 12v DC.

 

[ante1]

I don’t really see the point here. Why convert mains to 12VDC and back to mains for a motor instead of running the motor directly from mains???

 

[grmahun]

Hi, Ante. Sorry to be late.
The original project is to feed an ac induction motor using voltage
source inverter(VSI).So this first needs dc input from one of the
following: battery(solar power),diode bridge rectifier or chopper.Using
this as an input the inverter gives an output of AC.But this AC is variable
in voltage and frequancy magnitude so that the torque and speed of the
motor can be controlled.

 

[electronicavr]

Hi,

What are the expected output ratings?

i need a circuit or design that:
convert a dc voltag(for example 24 or 60)to three phase voltag whit 60 volt or less
or 60 volt ac(single phase) to 60 or 70 volt three phase
amp=1 amp or less
thank

 

[ante1]

Hi, Ante. Sorry to be late.
The original project is to feed an ac induction motor using voltage
source inverter(VSI).So this first needs dc input from one of the
following: battery(solar power),diode bridge rectifier or chopper.Using
this as an input the inverter gives an output of AC.But this AC is variable
in voltage and frequancy magnitude so that the torque and speed of the
motor can be controlled.

An induction motor is not easy to regulate.