Blown transistor on multiple AX1500s

We are a frequent user of various roboteq boards.

For the majority of our applications, we use 12VDC motors.

For a new project, we have switched to 24VDC.

We have two Danaher linear actuators wired to a single AX1500.

These are running at 24VDC, and I set the current limit to 10A.

We have blown two different AX1500s. We even had different actuators (danaher, but different model) when we fried them. This most recent time, a second chip caught fire.

Has anyone experienced this problem?

I monitored temperatures, but did not see anything unusually high. This most recent problem occurred after I had been running the actuators for a few minutes. A few minutes before the "pop", I had checked the mosfet temps with an IR temp probe. None of the mosfets were above 35C.

We have a spare 3500 that I may try, but I am really unsure as to the cause. Especially when there are current limits in place for this type of behavior.

See below for pictures of the two boards with blown chips...
<img src="www.niitek.com/%7Eslauziere/IMG_1851resize.jpg">
<img src="www.niitek.com/%7Eslauziere/IMG_1855resize.jpg">

I should also add that none of our interconnects were melted when this happened.

Going out to the motors, the cabling is about 10feet. The cable to each actuator is four pieces of teflon-coated 16AWG wire. (Two for M+, two for M-)

This is a very unusual situation. Certainly, you should not connect another controller until the problem is understood.

The first picture shows the driver of Channel1 blown and the mosfet of Channel 2 exploded.

24V should not be a problem at all.

Note that if there is a short circuit, it is very possible to have hundred of Amps in the MOSFETs and cause destruction with only low current flowing from the battery, and therefore escaping current limiting.

Are the AX1500 used as dual channel or as single channel configuration?

Which firmware revision are you running?

Please contact us directly at <A href="This email address is being protected from spambots. You need JavaScript enabled to view it." target=_blank>This email address is being protected from spambots. You need JavaScript enabled to view it. for further troubleshooting. Attach a wiring diagram on how the actuators are connected to the controllers.

Thanks cosma.

I have sent an email with the requested info.

Cosma,

I have found that on the two boards that have blown transistors, there is a short between Vmot and M2-/+ (one is shorted with +, the other with -).

We had hooked up another 1500 with 20A fuses between M+s and the motors. I had run the system for a short while, trying to tune the loop. Never had a fuse blow. I then recently checked, and there is a short now between M2+ and Vmot. This, of course, causes weird behavior. M2 will not retract, and will only stay stationary when a negative position is given.

I will send you an email with more info.

Thanks,
Steve

Looks like the short is isolated to the transistor, and not other components, which I imagine makes sense.

The third board had apparently reached the point of shorting, but not catastrophic failure.

Hi Slauziere,Cosma,

I seem to have just struck a similar problem to yours, been running a 24V system using a Ax2550 for the main drive motors so I have also been running an Ax1500 on 24V for auxilary 12V motors. I have been runing in closed loop servo mode and set my current limit to 10A.

Was there any resolution to your problem? I'm wondering if some 12V motors near stall could be an effective short?

@slauziere: I know its been a long time since you posted your issue, I am just curious were you able to sort it out? I sincerely don\'t have any idea what might have gone wrong but I think since the board was made for 12V, going for 24V would have fried the components. cosma\'s suggestions are also not bad, most of the stuffs make sense.

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