blown AX2550

12 years 5 months ago #25026122 by tmachi
blown AX2550 was created by tmachi
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Could you guild me as to what might cause an AX2550 to be damaged? <SPAN style="mso-spacerun: yes"> </SPAN>The documentation suggest that the controller protects itself from over current and over voltage, but reading through the online forum, I see that that’s not true for all cases.<SPAN style="mso-spacerun: yes"> </SPAN>I have a very low impedance motor (16mohm) driving a high inertia load.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>I have damaged two of these controllers so far. <SPAN style="mso-spacerun: yes"> </SPAN>I don’t want to try another one until I can get some idea as what is causing them to fail. Detail about the system and failure follows.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Appreciate any help you can offer.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Problem:</FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">Damaged AX2550 (SC) motor controller.<SPAN style="mso-spacerun: yes"> </SPAN></FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>The system has two controllers, only one of the two fails (on the same side).<SPAN style="mso-spacerun: yes"> </SPAN>Two separate times. </FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Not sure when it blows, accel? Decel? Or other?</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Selftest fails</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">Firmware version: v1.9b<SPAN style="mso-spacerun: yes"> </SPAN>06/01/07</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Hardware code: 2-0-1<SPAN style="mso-spacerun: yes"> </SPAN>(4 fet per leg, single ch)</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>7 seg displays a 'J' in one direction and an upside down 'A' in the other.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>None of the transistors are visually damaged.<SPAN style="mso-spacerun: yes"> </SPAN>(Though I can’t see all of them. I have not removed the brd from the heat-sink.)</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Drain to source is not shorted , nor it’s open</FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Gate to Source is ~4.4Mohms on some of the transitors and ~500Kohms on some.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>The motor is not shorted to it’s frame.<SPAN style="mso-spacerun: yes"> </SPAN>If it has a winding short, I have no way to tell (since it’s only 16mohms normally).</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>System:</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Motor controller:</FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>2 AX2550 (SC) motor controllers, </FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>analog mode</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>except for analog mode all other configurable parameters are factor default </FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">Battery:</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>36 volt. </FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>75 AHr</FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Motor: </FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>Perm motor GmbH</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>PMG 132 – S43</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>R = 16mohms</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>L = 0.019 mH</FONT></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman"><SPAN style="mso-spacerun: yes"> </SPAN>I = 0.025kgm2</FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Two of these motors drive a ~350lb rubber track robot.<SPAN style="mso-spacerun: yes"> </SPAN>One motor for each track, one AX2550 (SC) for each motor.<SPAN style="mso-spacerun: yes"> </SPAN>Driven to as much as 10 ft/sec, with various (but fairly aggressive) accel and decel rates. </FONT>
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<SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA">During operation, one controller is ramped to a 50% power command via it’s analog input. The other controller’s analog input is determined by the output of an external PID that closes the loop on that tracks position.<SPAN style="mso-spacerun: yes"> </SPAN>The PID controlled track follows the open loop tracks position.</SPAN>

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12 years 5 months ago #25031358 by Adamj12b
Replied by Adamj12b on topic Re:blown AX2550

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12 years 5 months ago #25054798 by cosma
Replied by cosma on topic Re:blown AX2550
These motors have indeed caused us problems in the past. At the time, they would cause systematic damage during rapid decelleration because of their high inertia: we measured up to 500A of current burned off in the MOSFETs. This was also causing negative voltage spikes that killed the MOSFET drivers.

These two problems have been addressed by limiting the negative Amps with firmware change (starting with version 1.7) and adding protection device that absorbed the negative spike.

These motors are still capable of great stress to the controller, however.

If there is no visible damage, measured short, or smell of burn, there may be hope that damage is limited.

Connect the controller to the PC and check it with Roborun. Verify that it can communicate with the PC. Using the Run tab, verify that internal voltage is 11.8V. Use the sliders to exercise the motor.

Please use our support form at <A href=" dev.roboteq.com/dev1/form-support.html " target=_blank> dev.roboteq.com/dev1/form-support.html for personalized assistance.

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12 years 5 months ago #25062333 by tmachi
Replied by tmachi on topic Re:blown AX2550
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Thanks for the reply,</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">I have checked the controller with Roborun.<SPAN style="mso-spacerun: yes"> </SPAN>Yes it can comm. The internal voltage is 11.8.<SPAN style="mso-spacerun: yes"> </SPAN>It will run in a limited capacity.<SPAN style="mso-spacerun: yes"> </SPAN>This was true on the robot as well. It’s as if only one channel is bad, though I can not discern a difference between the two sides with an ohm meter.<SPAN style="mso-spacerun: yes"> </SPAN></FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>There is no burn smell, and no visual damage.<SPAN style="mso-spacerun: yes"> </SPAN>I wonder if that tells us that the failure mode is a high (or neg) voltage event instead of a high current (thus thermal) event?</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">When you write of testing with this motor, and of it’s high inertia do you refer to only the motor inertia?<SPAN style="mso-spacerun: yes"> </SPAN>The “system” inertia for this robot is many times the motor inertia.<SPAN style="mso-spacerun: yes"> </SPAN></FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">Limited damage would be great, it should be easier to repair.<SPAN style="mso-spacerun: yes"> </SPAN>But the most important question is, “What caused it?”<SPAN style="mso-spacerun: yes"> </SPAN></FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>I need to understand if the AX2550 is undersized for my application or if there is some characteristic about this motor that damages the controller.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT size=3><FONT face="Times New Roman">Where can I find a specification for the controller that tells me what currents and power are within it’s limits (for re-generative braking decel cases)?<SPAN style="mso-spacerun: yes"> </SPAN></FONT></FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Do you have any detail on the neg voltage spikes failure mode.</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Can you guide me to a similar motor that would be more compatible with your controller?</FONT>
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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Do you have another controller that would be more compatible with this motor? </FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman" size=3>Appreciate any help you can offer.</FONT>

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