My EV truck does have an overspeed sensor (a sensor sitting next to the rear shaft of the motor, which has a pulley for the steering pump belt and that pulley has an extra screw which passes in front of the sensor, so only one pulse per rotation, I believe though I did not bother to inspect the pulley if it might have 2 or more bolt heads sticking out that result in more pulses per rotation.
One of the ways to detect overspeed is to measure the distance between two pulses from the sensor and compare that this is always at least a certain minimum, if it gets too low the power must be cut back. This can be done in a processor and a hardware timer measuring the time between pulses, or even in a simple monostable multivibrator, first one that is triggered by one edge of the pulse from the sensor and stretches it by a configurable amount of time, such that when the max RPM is reached the output no longer returns because it is re-triggered before the pulse stretch finishes. It is easy to detect (by a second one) that the signal level no longer returns and cut power. Another nice feature build-in to my controller is a detection of overcurrent. At a certain configurable maximum the power is reduced to maintain the current at max, but if the current rises to a next threshold level, the contactor is dropped. Before closing the contactor (during starting) the controller also senses whether the controller output is free floating and not stuck due to blown transistor or fly back diode. Either will avoid starting and these features have saved me from turning my motor into shrapnel or blowing stuff up more than it already was, since my switching IGBT tends to self-destruct once in a while due to errors in the layout of the controller. Note: this is the EV versoin of an old "forklift" DC controller, EVT-100 Hope this gives some ideas, Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Bill C. via EV Sent: Friday, January 15, 2016 12:02 PM To: ev@lists.evdl.org Subject: Re: [EVDL] Series motor overspeed protection >The evdl member must be new as their email is incorrectly set to send out their text as a html attachment Sorry about that, my hosting provider recently changed their webmail system and wiped out all the previous settings for text vs HTML, sender's name etc. I think it's fixed now. >Please tell us more details of your conversion: make, model, year, and how you are driving it. It's a 2002 Ford Focus with and ADC 9 inch motor and Curtis controller, driven mostly on flat roads. It's wired to open the main contactor when the accelerator is released, so I'm not too worried about shutting it off if the controller fails. I'm concerned about shutting off the motor if the accelerator is pressed and the clutch is in or the transmission is in neutral. I know not to do that, but it will be driven by a state inspection technician and possibly other people not familiar with EV conversions. Bill -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Series-moto r-overspeed-protection-tp4679797p4679804.html Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
