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Dynamic load test

A project log for EverywhereElectric

Motor control/monitor system for a fully featured EV (bike, board, etc), >1KW 3phase motor control, Android control interface and hardware.

JarrodJarrod 10/22/2014 at 22:021 Comment

The fun stuff begins, motor is spinning but to make software changes we need a bench test setup, this will make it easier to profile the controller and add/verify new features. As opposed to duct-taping multimeters all over a pushbike!

To actually provide a load for the motor on the bench, it is directly coupled to a DC treadmill motor, 180V 6.5A 1HP rated. This acts in reverse as a generator. An electronic load for this generator is required for its use as a variable mechanical load. I figured constant current loading would make it easy to ramp up the mechanical load (since torque is proportional to motor/generator current) but after playing around I think constant power might be more useful, I might use a microcontroller to simply vary the load current depending on generator voltage, or even use the encoder on the generator to implement some sort of torque/speed curve.

The electronic load is simply a MOSFET operating in it's linear region. It's cooled by a PC heatsink. An opamp drives the gate, it compares the voltage across a current shunt and a reference voltage to control the current. I'm using a potentiometer to set the reference voltage but it could just as easily be a microcontroller.

Anyway, video below shows the constant current load getting destroyed by the sheer power of Everywhere Electric ;-) More load FET's needed, as it fails short circuit at around 500W which is actually a very good test, hitting a large load under throttle is what blew up the last revision. This one survived with grace.

Note to self: set up an LCD to show motor controller statistics in real time.


Discussions

robertwilliamsonnorwich wrote 11/02/2014 at 16:31 point
Fantastic project, kudos for your hard work and best wishes for your continued perseverance and success. I stumbled upon this project whilst googling a 1kw f.o.c ebike controller. I have only the most basic understanding of electronics, however I can appreciate the many benefits of F.O.C. Your PCB is an ideal size for an ebike and far smaller than any others I have seen. The generous fet heat sink can only be beneficial.
Please forgive my noobness if the answers to my following questions could be summised from the information already presented.
Will it be possible to limit/ramp phase amps?
As I understand it the head unit has computational power, and communicates with the controller cpu to assure no spurious signals are sent to the controller. Sort of failsafe/redundancy idea, is this right?
Will it be possible to connect to a p.a.s. disc and to tune motor response accordingly?
At present would the controller be safe with 57.4v H.O.C?

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