The battery is not the only thing that supplies current to the motor. The switching of the controller connects the motor to the battery for a period of time, followed by a period where the "freewheel" (diode or transistor) inside the controller carries all the current, also during the time that the motor is connected to the battery, it is not just the battery but also the capacitors in the controller that provide the current. Wiring the motor to the contactor instead of to the controller itself, creates a large loop and increases the inductance which can affect the operation of the controller, besides creating a lot of noise from the high frequent switching and the large "antenna" loop created by the wiring conncted to different points. Some people even twist the motor leads together to minimize the effective area inside the loop created by the two motor leads, to further reduce the noise radiated from the output of the controller. especially nearby sensing wires such as throttle control or sensor inputs can be affected by hundreds of volts fast-switching nearby and generating large amounts of noise due to improper wiring.
-----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of EVDL Administrator via EV Sent: Saturday, December 16, 2017 10:32 PM To: firstname.lastname@example.org Cc: EVDL Administrator Subject: [EVDL] DC controller common terminal This question refers to a non-road EV, but I think it's applicable to road EVs too. I recently bought an Alltrax controller for my Elec-trac tractor. Like most (all?) DC controllers, it has 3 high power terminals. In this case they're B-, M-, and B+M+ (actually marked just B+ but described as the B+M+ terminal). The printed manual with it contains the following intriguing warning. It's printed in boldface type and underlined text (in parentheses, quotated, capital letters ... no, wait, that's something else). "Connect the motor leads as shown, making sure that you connect the B+ power lead from the contactor and the A1 motor lead AT the B+ terminal of the controller. This is important for proper controller operation." I read this as meaning that I should NOT, say, run a single cable from the contactor "downstream" side to the controller B+M+ terminal, and then connect the motor A1 lead to the contactor at that "downstream" terminal. Instead, the motor A1 lead should be extended to the controller B+M+ terminal, so that there are 2 lugs on that controller terminal. View following with a monospaced font such as Courier: RIGHT: |--------------------- | | | Motor B- |M- B+M+ | |---------() -() ()-------------- - | --- | - | --- | |___________________| Battery Controller Motor WRONG: |--------------------- | | | Motor B- |M- B+M+ | |---------() -() () | - | | --- | | - | | --- | | |___________________|______________| Battery Controller Motor I've previously connected DC controllers the "wrong" way -- that is, connecting the motor lead to the contactor when it made for a shorter motor lead. It seemed to work fine. I guess my ignorance is showing here. Can someone explain why connecting the motor directly to the common controller terminal, not some other terminal feeding it, would be "important for proper controller operation"? David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org 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 Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)