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Forum Index : Electronics : 3 phase inverter for AC induction and servo motors

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Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 09:37pm 06 Dec 2021
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  poida said  More power:

a few ways to go about it

1 - two or more inverters, running independent control loops and with differing
output and phase. Place AC loads on each inverter to distribute load.


That sounds like the most practical solution, and it offers excellent redundancy if a problem should arise.
Cheers,  Tony.
 
Revlac

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Joined: 31/12/2016
Location: Australia
Posts: 642
Posted: 12:21am 07 Dec 2021
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  Quote  1 - two or more inverters, running independent control loops

I would agree, nothing wrong with having more than one inverter, have been running 2 for some time, one runs the house the other runs some of the power points on one side of the house and any other large loads thrown at it with out affecting or worry about the load on the house inverter, some power can be switched from one to the other via a change over switch, one way only.
There are a few inverters available that can be paralleled up to 9 units or so.
With three phase there can be a few options depending on what you need, 3 singles or whatever, even some 3phase generators can be rewired to single phase without much trouble......wonder if that could be done with a 3phase inverter.
Cheers Aaron
Off The Grid
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 04:00am 07 Dec 2021
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I suppose just a single phase inverter would be all that is needed, but with the facility to phase lock 120 degrees out of phase with an external reference input, or free run all by itself.
Cheers,  Tony.
 
Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 376
Posted: 04:58am 12 May 2022
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Poida,

What are your thoughts on adding software programmable dead time into your mega code, and having 6 separate pin outputs go to the 6 individual Mosfet/IGBT drivers?

The obvious problem is that it could be easy for a software error to turn on both high and low side drivers, which would really let out the smoke. But what is the genuine risk of something like that actually happening?

If the mosfet driver logic is not inverted, all mosfets are off on startup, so I can't see any immediate problem.
 
poida

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Joined: 02/02/2017
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Posts: 1114
Posted: 12:00pm 14 May 2022
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the Mega can't do deadtime. It can make the 3 simple PWM outputs
that is then sent into IR2184 type ICs to create the two outputs with deadtime
for each half bridge.

The Arduino Due can do deadtime and produce 3 PWM with complimentary outputs
but it's a bit of an obsolete thing now. I still like them tho.

The other choice seems to me to be STM32

Lately I have been wasting time playing with STM32F407 micros
such as this but I paid only $10 years ago
and I have 3 phase output with complimentary PWM and deadtime
working now.

I spent a day trying to get a Blue pill board (using the STM32F103)
to do the same but even though the code is the same and STM manuals say
they have the same TIMER1 hardware, it does not do deadtime, just
the complimentary outputs for each of the 3 channels I need.

These are also rather too old and now the smart kids are on to
STM32F411 Black pill boards.these
and they are cheap as chips.
I will get a couple of them and see what they can do.
wronger than a phone book full of wrong phone numbers
 
poida

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Joined: 02/02/2017
Location: Australia
Posts: 1114
Posted: 12:32pm 14 May 2022
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anyway, the previous post was dribbling on about micros that do the proper 6 outputs.


I have confidence that I could program something like a STM32F4xx micro to
produce 3 phase complimentary outputs with deadtime
features of this would include:
variable deadtime
no outputs until the firmware boots and completes initialisation
complete control over output amplitude and frequency (a VFD drive is easy to do!)
no uncontrolled outputs at any time, including low level start up or brown outs


I am close to starting making a power board for 3 phase 240V AC experiments.
It will use optocouplers for gate drive and isolated dc-dc converters for the
3 high side gate drives. No gate drive ICs needed since the signalling will
be the 6 signals of the 3 phase/comp output + DT from the STm32F4

firmware will have either single AC voltage feedback or individual AC phase feedback.
one or the other to be enabled via jumper or user config.

What I like about using the IR2184 chips is that the gate drive outputs
can be disabled by default via a pull down resistor.
This pin is driven high by firmware to enable output.
The Arduino Nano and Mega can have digital output pins configured
so that their outputs are ALWAYS LOW from no power/during boot/running code
stages. This means a pin will be LOW until and only until the code is active, booted
and intialised and then drive it high. This pin would be taken to the
IR2184 shutdown pin. This is how I do it with the nanoverter and the picoverter.
cross conduction is prevented thanks to the IR2184 logic and tight control
of it's shutdown pin levels

The more I think about it, the cost of 3 IR2184 plus 3x 10uF caps and 3x diodes for the 3 charh pumps is way cheaper and easier than having 6 optos + 3 dc-dc converters
and needing the 6 pwm outputs with pwm and guaranteed deadtime and no uncordinated outputs during boot/brownouts
wronger than a phone book full of wrong phone numbers
 
Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 376
Posted: 12:54pm 14 May 2022
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Good stuff Poida.  I've designed a 3 phase 200v IGBT board at my end. I have sent the design away and I'm just waiting for it to be manufactured. I can send you one if it will help you out? It uses UCC5350M gate drivers and is supposed to work with the EG8030 carrier board. It uses my favourite Hi-Link 3w power supplies for gate drive power supply.
 
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