83 lines
3.0 KiB
Plaintext
83 lines
3.0 KiB
Plaintext
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<!-- { "title": "Three Phase Inverter" } -->
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<h1>#title#</h1>
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<p>
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Already when I was still in school, about 30 years ago, I was curious to make an inverter using some MOSFETs. I actually was able to build a simple one phase inverter with rectangular signal shape (I used a NE555). Using this thing I drove a transformer to light a blub. However, all of these inverters I built passed by in fire.
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</p>
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<p>
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Now, I tried it again, not longer using MOSFETs but IGBTs with free-wheeling diode. Moreover, I used some microcontrollers and sine values to feed a PWM to get a sine-alike signal shape. And this time I was able with three phases to drive an asynchronous motor.
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<a href="files/img_0053.jpg"><img src="files/img_0053.jpg" alt="img_0053" width="730" height="973"/></a>
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</p>
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<p>
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The signal shaping is done with four MSP430 controllers, three as PWMs to drive the bridge and one to coordinate and control the three PWMs. The PWM controller is decoupled from the IGBT driver (IR2184) using optic couplers.
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</p>
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<a href="files/img_0054-e1476437702547.jpg"><img src="files/img_0054-e1476437702547.jpg" alt="img_0054" width="730" height="548"/></a>
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</p>
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<p>
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The bridge is a three phase IGBT module is a 6MB120F-060 I got for a few euros at ebay.
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<a href="files/img_0055-e1476437685461.jpg"><img src="files/img_0055-e1476437685461.jpg" alt="img_0055" width="730" /></a>
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</p>
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<p>
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To avoid high voltages in my setup I got a 24V async motor, also from ebay.
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<a href="files/img_0056.jpg"><img src="files/img_0056.jpg" alt="img_0056" width="730" height="548" /></a>
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</p>
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<p>
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The PWMs generate the signal from a sine table generated using Excel. Those I got this signal:
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</p>
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<p>
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<a href="files/inverter0_2016-09-23-4.png"><img src="files/inverter0_2016-09-23-4.png" alt="inverter0_2016-09-23-4" width="640" /></a>
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</p>
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<p>
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The main task of the coordinator is the start the PWMs with a phase shift of 120° (digital line 1, 2 and 3):
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</p>
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<p>
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<a href="files/10/2016-10-13_1.png"><img src="files/2016-10-13_1.png" alt="2016-10-13_1" width="640" height="520" /></a>
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</p>
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<p>
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Currently the PWMs start with random polarity. The interesting signals are the digital lines 4, 5 and 6.
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</p>
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<p>
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Sometimes the motor runs:
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</p>
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<p>
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<a href="files/2016-10-13_works.png"><img src="files/2016-10-13_works.png" alt="2016-10-13_works" width="640" height="520" /></a>
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</p>
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<p>
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But sometimes not:
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</p>
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<p>
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<a href="files/2016-10-13_works_not.png"><img src="files/2016-10-13_works_not.png" alt="2016-10-13_works_not" width="640" /></a>
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</p>
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<p>
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<s>
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The firmware is available on bitbucket, for the PWM controllers <a href="https://bitbucket.org/wollud1969/inverter0.git" target="_blank">here</a> and for the coordinator <a href="https://bitbucket.org/wollud1969/inverter0ctrl.git" target="_blank">here</a>.
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</s>
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</p>
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<p>
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The firmware is available on Gitlab, for the PWM controllers <a href="https://gitlab.com/wolutator/inverter0" target="_blank">here</a> and for the coordinator <a href="https://gitlab.com/wolutator/inverter0ctrl" target="_blank">here</a>.
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</p>
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