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Broken Phases on T200 thruster

Good Morning :slight_smile:

Unfortunately, our ROV decided to turn into a thruster eating monster.

We are using T200 thrusters running at 12V controlled by basic ESCs (one of the earlier versions). During the last two weeks we had 4 thrusters breaking down. After checking all the phases we discovered that two phases are broken on all of them (Resistance approx. 1 MOhm). Mechanically the thrusters appear to be in good condition. No corrosion or debris at the stator.

We have replacement thrusters ready to go, but wanted to make sure that we don’t burn through any more thrusters. Has anyone experienced a similar problem or has any idea to what could cause the phases to break?

Our first guess was that the cables are broken. So we cut away one cable, up to the potting, but there was no difference in the resistance measurement. So we assume that the defect must have occured somewhere in the coil. Is it possible that this is caused by vibration or an actuation frequency that is too high?

Thank you for your help,


Hi @engler-christian,

If earlier batches of thrusters were run more aggressively without ramping the throttle, it was possible for the stator to flex on the stem over time and potentially break the phase wires where they pass through the base. Please email support@bluerobotics.com with your order numbers, and we will be able to further assist.


Hi Adam,

Thank you very much for your answer. This may very well be the case, since the thrusters were older versions and we ran them quite agressively on times.

Are the latest versions of the thrusters less prone to this problem?
We also adjusted our controller to run the thrusters more smoothly so our replacement thrusters should be fine.

I will send an email to support.

Your answer certainly puts our mind at ease, and we can now confidently replace our thrusters :slight_smile:

Thanks again and best regards,

The stem has been strengthened to resolve this issue.

Thank you for your reply! To follow up on our issue: We replaced all our old thrusters with new ones and did not have any more breakages. Even though the thrusters are still run quite agressively, they hold up very well :slight_smile: