This sounds similar to what has happened with many brush motor controllers where the distance from the batteries to controller is long and the load high.
The controller is limited in space internally and so there’s only so much bulk capacitance that can be placed at the power input to the controller.
While it is enough capacitance for many instances, the combination of long battery cable lengths, high loads cause either the output silicon devices to fail or the capacitors themselves due to overvoltage.
A straightforward solution is to add external bulk capacitance across the switched power cables near the motor/controller.
In doing so, both the PWM switching transient stresses on the controller as well as the stress induced by the sudden unloading of the long battery cable will be reduced.
It also sounds as if his main power switch is remote from the motors. If so, he should instead be driving a remote contactor/solenoid located near the motors to switch power On/Off.
Also, in doing that, he’ll want to consider adding the very common precharge resistor across the main contactor to precharge the controller’s capacitors and electronics-
Some of the above may not apply to Torqeedo, but it is very common and applicable to the more traditional EV-scale brush motor controllers.
Search for “curtis precharge resistor”, eg. check out the diagram at the bottom of this page: http://evhelp.
In case this helps-
-Myles Twete, Portland, Or.
From: electricboats@
Sent: Wednesday, December 23, 2009 12:37 PM
To: electricboats@
Subject: Re: [Electric Boats] Re: Electric Catamaran
Hi Matti,
Sorry I missed answering your question until now.
Yes to a degree I am familiar with what's happening with Bryan's Torqeedo's. The problem is the cooking of components in the the controller and the cause of seems related to long power cables.
On Bryan's cat there is quite a long run from the batteries to the motor on one side. On the trouble side the cable length is 17m total (that is, the electrical path to the motor and back).
He started with one Torqeedo on one hull and was using this for a short while until he got a second one. (maybe a few weeks?) And as it turns out, it is the second motor, that has done less work, that had the problem.
Because the only difference between the two motors is the length of cable its fairly clear that this is the cause, although not absolute. In other respects such as load, mounting arrangements and other service requirements they are identical.
I believe Torqeedo are doing tests to try to simulate this problem and if replicable will be able to design the protection needed.
The theory is that the root cause is high induced voltage created when the power is shut down quickly. Consider when the motor is under full power and the throttle closed quickly to the off position (such as when in a docking manouvre). When the current is flowing there is a stable magnetic field around the cables over the full length. When the power is shut off the field collapses, and in collapsing the lines if flux cut the cable and induce a voltage. Because of the long cable length the voltage spike is high enough to cause a problem.
The Australian distributor, Claude Desjardins, has been really supportive and has supplied replacement parts to get Bryan going again, and has lent him another battery pack to use so that the cable lengths are short. Bryan is off cruising somewhere now, up around Hervey Bay I think. In the meantime its up to Torqeedo to continue with testing to prove one way or another if that is indeed the problem.
On my boat I have used the standard cable that comes with the Torqeedo so I have no concerns about this issue.
Cheers
Chris
On 16/12/2009, at 12:40 AM, MattiB wrote:
Hi Chris
I just read on another forum that Bryan with School's out has had some problems with his torqeedos and their controllers. Have you heard anything about it, since you are also located in Australia? Do you know if the problem is solved and what caused it? I think he also had e-pods before he converted to torqeedo...
greetings from the dark north
Matti
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