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Topic: Three phases, high current ! (Read 2771 times) previous topic - next topic

albortega

Hi everyone,

I am trying to create a three-phase current system with an Arduino. I will control a linear induction motor with it. I have managed to have three signals with three different phases using the PWM outputs. The problems is that I need high current: 10 amperes, or 20 amperes if possible.

My question is: is there any shield I can use to control it? I know there are dual-motor shield controllers but here I need a three-phase one. Any ideas?

Thank youo in advance for your time guys!

Paul_KD7HB

The size of the heat-sinks you will need, as well as hand wiring will determine what you need. Circuit board traces cannot possible handle that much current.

Paul

albortega

Hi Paul,


Thank you very much for your answer!

I have seen this kind of shield for DC motors:

http://www.robotshop.com/en/10a-dc-motor-driver-arduino-shield.html

Apparently you can run up to 10 Amp in continuous and I wonder if there is something similar with 3 outputs. Or maybe you think I could use 2 of them to create a three phase current?

MarkT

#3
Nov 10, 2015, 11:23 am Last Edit: Nov 10, 2015, 11:25 am by MarkT
What voltage?  You probably want a 3-phase bridge module (so called "intelligent power modules"), but voltage
will determine whether MOSFET or IGBT is appropriate.  For that current level an IGBT module will be
large and designed to bolt on to a substantial heatsink, MOSFET one might be a little more managable.

At 20A or so you'd normally use copper strip, not PCB for construction, but thicker copper
PCB is available.  Remember as current doubles you need 4 times as much copper for the
same heat dissipation so 20A is a different game to 10A

For instance a 600V 30A module: http://uk.farnell.com/fairchild-semiconductor/fpdb30ph60/ipm-igbt-30a-600v-spmga-027/dp/2322637
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albortega

Thank you again MarkT! I am checking that, honestly I don't know very well how to use them, but it looks like the kind of thing I need.

My device is just a steel core where I have put some coils. Now I need three signals with different phase and high current to make this assembly create a moving magnetic field that will make aluminium plates move.

I will check how I can use this modules MarkT! Thanks again :)

Paul_KD7HB

Thank you again MarkT! I am checking that, honestly I don't know very well how to use them, but it looks like the kind of thing I need.

My device is just a steel core where I have put some coils. Now I need three signals with different phase and high current to make this assembly create a moving magnetic field that will make aluminium plates move.

I will check how I can use this modules MarkT! Thanks again :)
You surely don't intend to use a SINGLE transformer with three phase!

Paul

albortega

What do you mean Paul?

I also think that maybe I could reprogram a ESC. Anyone has an idea of how could I flash and reprogram the ESC to control it ( with my motor I won't have a back emf...)

MarkT

ESC won't drive a non-synchronous motor well I suspect, but it would be an interesting
experiment - don't think I've heard of anyone trying it.
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Paul_KD7HB

My device is just a steel core where I have put some coils. Now I need three signals with different phase and high current to make this assembly create a moving magnetic field that will make aluminium plates move.


All the three phase power I have ever seen with transformers use one transformer per phase. The 3-phase step-up transformer in my plant is a big steel box with three separate transformers inside.

Have you researched the interaction between the three coils?

Paul

Boardburner2

Hi everyone,

I am trying to create a three-phase current system with an Arduino. I will control a linear induction motor with it. I have managed to have three signals with three different phases using the PWM outputs. The problems is that I need high current: 10 amperes, or 20 amperes if possible.

My question is: is there any shield I can use to control it? I know there are dual-motor shield controllers but here I need a three-phase one. Any ideas?

Thank youo in advance for your time guys!
what voltage is you motor running at ?

albortega

Thank you everyone for your answers again!

The motor is a linear induction motor, quite small. I want to have 20 amperes in my coils. They are gonna be thick and the impedance is gonna be low. I don't want to use very high voltage but I suppose I will be at 50 v at least. Right now they run at 12V but I just manage to have 0,7Amp through my coils. Another option would be to use transformers to work at a lower voltage, but I don't see standard transformers that suit exactly my requirements: from 12 volts and 0.5 ampers to 20 ampers ( ant whatever volts I have to have)

@Paul: what do you mean the interaction between my three coils? The induction between them? Honestly I have not researched about that.

 I think a square signal, like the one create by the ESC, would be enough to make my motor work. Maybe also an inverter could work, but I don't know how to build and manage it: maybe I could control the amplitude of my three-phase currents with the value of the DC current, but I don't know how to control the frequency.

It is not as easy as I though it would be...

MarkT

If 12V gives you 0.7A, 50V might give you 3A at best. 

You drive induction motors either with 3-phase PWM signals or with bang-bang vector control - both
attempt to give clean sinusoidal 3-phase currents spaced at 120 degrees (the first by emulating
sinusoidal average voltages, the latter by feedback loops continually monitoring the current and comparing
to a synthesized 3-phase signal.

3-phase PWM involves using 3 PWM outputs in phase-correct mode set to 50% - this gives zero drive
as each phase sees the same voltage as each other.
You then perturb the duty cycle of each output around 50% in sinusoidal fashion.  Its magic and simple
with the Arduino Mega as the 16 bit timers typically drive 3 PWM output each on that board.
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albortega

Do you think it could work if I use a normal transistor ( that can manage 10 amp or 20amp) and control it with an arduino (PWM signal) to get one phase? With three transistors I would get my three-phase system!


MarkT

Can't work, each phase needs two switches.
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TomGeorge

Hi,

Can you post an image of what your 3phase PWM signals look like that you are getting out of the arduino please?

Thanks...  Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

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