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Topic: Three phases, high current ! (Read 2779 times) previous topic - next topic

albortega

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:
http://interface.khm.de/wp-content/uploads/2009/12/ddd_sine_pwm.jpg

TomGeorge

Hi,
So the top trace is representative of what your arduino is producing?

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

albortega

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!

MarkT

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.

Quote
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.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomGeorge

Hi,

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

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