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!
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
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?
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
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 
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
You surely don't intend to use a SINGLE transformer with three phase!
Paul
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...)
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.
albortega:
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
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!
what voltage is you motor running at ?
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...
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.
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!
Can't work, each phase needs two switches.
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....
MarkT:
Can't work, each phase needs two switches.
Why do you say it won't work MarkT? The transistor will work as a switch, won't it?
Tom, it is not my original but I get something like that:
Hi,
So the top trace is representative of what your arduino is producing?
Tom....
TomGeorge:
Hi,
So the top trace is representative of what your arduino is producing?Tom....
Yes! Then you can use filters, or directly the signal that your motor will see is the sinusoide!
albortega:
Why do you say it won't work MarkT? The transistor will work as a switch, won't it?
Each phase needs two switches, not one. Its a half-H-bridge per phase. This means
a high-low MOSFET driver chip and two MOSFETs (or IGBT's) per phase. Or one of those
modules I linked to earlier which has all 3 phases in one module.
Yes! Then you can use filters, or directly the signal that your motor will see is the sinusoide!
You don't filter the signal at all, the inductance of the motor does that for you - the current
is sinsoidal, the voltage is chopped.
BTW your PWM signal seems to be bandwidth-limited, which will cook the switching devices.
Clean fast switching edges are essential for high power bridges, or you'll dump 100's of watts
into the switching devices.
Hi,
You don't filter the signal at all, the inductance of the motor does that for you - the current
is sinsoidal, the voltage is chopped.
Yes, that's what I was leading up to, leave it as a digital PWM for the switching bridge.
Tom.....
