3 phase inverter for AC induction and servo motors


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poida

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Joined: 02/02/2017
Location: Australia
Posts: 1114
Posted: 06:01am 01 Jan 2021      

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I had a look at the CY8CKIT-059uC and it's a very intriguing device.
I love the built-in opamps and completely configurable hardware,
that can be reconfigured on the fly during program execution.
It's really nice.

I will be staying with the Mega since I know that micro architecture well.
Learning new micros might be easy for the young people but for me
knowing the ATmega, Cortex M3 (Arduino Due), STM32F1 and STMF4 is enough.

The above code is about 2/3 of the final code needed to run as an inverter.

I have spent some time looking at the EG8030 documentation.
It comes in two flavours, Chinese and Russian. Google translate is helpful.

The EG8030 can run in a few different modes.
The first 4 are (all have soft start same as EG8010):

3 phase with closed loop voltage control for each of the 3 phases, so that
all 3 phases can be driven as needed to provide desired output voltage.

3 phase with closed loop voltage control taken from one phase or an external input
with all 3 phases driven in unison to provide an output.

The above but open loop. This is where the outputs are defined by the input
in a 1 to 1 mapping. When loads are applied, voltages will drop.

Other modes exist too.
And interestingly, there is a digital input used to reset the SPWM to Zero degrees
when triggered and this is used to synchronise multiple systems.

I will probably go with the first mode.
I want all 3 phases driven in a closed loop control, with each phase having it's own
feedback voltage. The output frequency will be 50 Hz for start up and a few seconds
afterwards, then reduce freq based in DC input power levels via a lookup table or something.
There will be soft start from zero power to full voltage taking about 3 seconds.
And a soft stop.

I have ordered 6 x IR2148 gate drive ICs. Only need 3 so have a spare set for when
things blow up. I need to collect a few bits - 3 x 12V transformers, chip sockets etc. And 3 good ferrite chokes, probably use the cheaper RS component ones.

Here is the suggested circuit for the EG8030
You can see the 3 1/2 bridge drives and the delta/wye transformer.
With 48V DC supply it suggests 20V AC primary winding which is a bit low to my mind.
There are no primary chokes. There are 0.47uF caps across the outputs which does not
seem right. I think we need correctly working LC filters with this but I can not see
the inductance of the transformerand the 0.47uF caps helping much.