Best Practices (Cycle Analyst, Shunts, single/dual Phase Runner, & accessory loads)?

[WalkerYYJ]

Hey all,

So working on my first build, which is a quasi long range cargo bike.
I have a custom power pack (1800 Whrs) that will be running one (potentially 2 phase runners), and accessories (lights, chargers, etc).
In a dual Phase runner config, what is recommended regarding current monitoring?

I have a CAv3 WP, would it be acceptable to grab an external shunt and suitable hardware to isolate the shunt pins on the HiGo?

Thanks,

 

[amberwolf]

If you need to monitor both PRs with one CA, then you'll have to use an external shunt in the battery negative of the supply to the PRs.

The blue and white wires from the CA (shunt + and -) connect to each end of the external shunt. It should have the + on the battery end of the shunt, and the - on the controller end. If you get a negative current reading when operating the controllers, reverse that.

The shunt needs to be greater than 0.75mohms if you want to use the standard (low range) CA mode, which gives greater "accuracy" of readouts, and also has less bugs than the high range mode.

 

[john61ct]

can dual PRs feed one motor?

 

[amberwolf]

Same answer for any multiphase bldc controllers. If you clock them so their timing is identical, perhaps. if not, you will at times have different parts of different bridges on each controller trying to feed the same phases. You can draw that out and see the current flow to figure out what that would do.

 

[BlueSeas]

Same answer for any multiphase bldc controllers. If you clock them so their timing is identical, perhaps. if not, you will at times have different parts of different bridges on each controller trying to feed the same phases. You can draw that out and see the current flow to figure out what that would do.

Is this even possible with the stuff out there today?

 

[amberwolf]

Same answer for any multiphase bldc controllers. If you clock them so their timing is identical, perhaps. if not, you will at times have different parts of different bridges on each controller trying to feed the same phases. You can draw that out and see the current flow to figure out what that would do.

Is this even possible with the stuff out there today?

Is which part possible? There are a number of different things in the statement you quoted.

 

[BlueSeas]

Same answer for any multiphase bldc controllers. If you clock them so their timing is identical, perhaps. if not, you will at times have different parts of different bridges on each controller trying to feed the same phases. You can draw that out and see the current flow to figure out what that would do.

Is this even possible with the stuff out there today?

Is which part possible? There are a number of different things in the statement you quoted.

Can you "clock" multiple bldc controllers so the timing is identical? The idea from the previous post. A single phaserunner will not handle the current requirements (or at least the power capability) of a QS 205 hub motor. But can you stack 2 phaserunners, or 2 of anything on the market to get more current?

 

[amberwolf]

Can you "clock" multiple bldc controllers so the timing is identical?

That would depend on the controller design more than most things.

The thing you have to make sure to avoid is ever having any upper phase bridge half of one controller turn on at the same time as any lower phase bridge half of another controller, for the same phase, because they're directly connected at middle of the bridge (where the motor phase wire goes), and if you ever turn them on at the same time, you just directly shorted battery positive to battery negative thru your FETs and inter-controller-wiring, which while pretty and often spectactular is rarely useful. If the event is short enough it may just cause excessive heating in those bridge halves, but if it keeps happening, eventually the heat could build up enough to cause a failure anyway.


Any set of identical sensored controllers that uses the same motor hall signals for all controllers in parallel has a chance of working, if all the gate timing has plenty of deadtime between cycles, so that shoot-thru simply never happens.


If the MCU and it's firmware allows you to connect them together to run off one synchronized clock signal, and it doesn't just sync up at the start of running, but does so at every control cycle, it would work. If timing drifts far enough apart to allow "shoot thru", you could (probably would) end up with gameover.

Any controller with opensource firmware could theoretically be programmed for the ability to do this "perfectly", if you know how to do it (I don't). You'd make one controller master, and the other(s) slave(s), and the master's control/timing signals would be used by the slave(s) MCU(s) to start and time their cycles from.

A single phaserunner will not handle the current requirements (or at least the power capability) of a QS 205 hub motor. But can you stack 2 phaserunners, or 2 of anything on the market to get more current?

Not unless you can keep them from ever having shoot thru.

IIRC it has actually been attempted successfully under some circumstances even with generic sensored controllers, though I don't remember the thread name and cant' find it in a 30second search. There's no guarantee it would continue to work, however, as any timing excursion that resulted in shoot-thru would make them go bang.



If you have a motor (or modify one this way) with two or more sets of phase wires, running to non-electrically-connected phase coils in the motor, then you could use any sets of controllers for this you like. (John in CR's "hubmonster" motors work this way) I don't know whether sensored or sensorless would work better in this situation; probably depends on what sensorless detection schemes are used and how the induction from one set of phase coils into the other affected that.

 

[BlueSeas]

I'm a pretty good tech, but no EE. I look at this like using multiple AC inverters or generators that have the ability to sync phase and share AC loads. But this is an advertised capability, including safeguards so the phases are in sync before the power is applied and the smoke comes out.

Your description of what's needed in motor controllers is how I understand the above to work. But it's an engineered capability. I've never seen this as an advertised capability in a motor controller. Sure the tech is possible, but to try this without the engineering to make it work? Seems a bit more complicated too? In AC power generation it's almost always a fixed 50 or 60 cycles. This makes it more static. My understanding of motor dynamics is weak, but would think this process would vary based on rotation speed. Can't see it as dependable unless the controllers are both looking at the same timing sources (easy), but also communicating between each other and agreeing in advance. That's not something implemented that I've seen anywhere. Not in a $500 device.

 

[amberwolf]

Seems a bit more complicated too? In AC power generation it's almost always a fixed 50 or 60 cycles. This makes it more static. My understanding of motor dynamics is weak, but would think this process would vary based on rotation speed.

Not only rotation speed (and rotor position) (which is what a single set of hall sensors would help sync), but also potentially with load and throttle amount (which affect the PWM duty cycle and possibly even timing, which could affect deadtimes depending on controller design.


If it helps, there are some threads and posts discussing this, some of which are found in this search
https://endless-sphere.com/forums/search.php?keywords=parallel*+control*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
and some of which report failure, some that don't say, and some that just speculate; couldn't find the ones that had success.

I'm a pretty good tech, but no EE.

I'm probably only a half-assed tech (definitely a hack), and definitely not an EE, but there are some things I can "see" in my head fairly well. I *think* that I can see how these current flows work, though I doubt I know even a thimbleful of what there is to know about motors and controllers.

 

[BlueSeas]

John in CR's example motor is really 2 motors in one. That's not something you can buy. That example is analogous to having both a front and rear hub motor with a controller for each one. That's easily doable.

 

[BlueSeas]

Don't sell yourself short. I've chased lots of electrons, but not in bldc controllers. You have far more than I. My follow up was both to see if I was missing something on the concept, but also in the context of John's question. The answer to can dual PR's run a single motor is basically not yet?

 

[amberwolf]

John in CR's example motor is really 2 motors in one. That's not something you can buy. That example is analogous to having both a front and rear hub motor with a controller for each one. That's easily doable.

Not exactly, as those have independent rotation speeds (albeit usually nearly identical assuming same size tires). More analogous to two motors axially linked with locked-together rotors (which has also been done). But even that isn't the same, as the hubmonsters are built with the windings all around the same stator teeth, which means that they also inductively interact, just not directly electrically (which is where the real big problem happens; induction *could* also cause problems but probably not like the direct short!).


You can actually do the hubmonster-like-thing yourself with many existing motors. You would open the motor and disconnect the phase wires from the windings, then separate the strands of each winding, dividing them up evenly into however many sets of windings you would like to have (meaning, how many controllers you wish to drive the motor with).

So if you had a motor using 8 strands of wire in each winding, you could use either 2, 4, or 8 controllers to drive the motor, with completely independent windings. If it had 9 strands, you'd be best using 3 controllers, or 9. I suspect that the more controllers used, the more likely it is to blow everything up at worst, or simply operate less than ideally at best, simply from inductive interactions between all the different controller phase current sets. But that would have to be tested to find out for sure. It might actually smooth out operation instead (but I doubt it).

The hard part is getting all the new sets of phase wires out to the controller(s), assuming typical axle type exits. There are ways to use larger bearings and cover modifications to run the wires between the axle and the bearing, and you could do literally any wiring you wanted that way, if you can machine yourself new covers. Or use a completely hollow large-diameter "pipe" axle, and have however much room you need by using a bigger pipe (but this requires a new mounting method or swingarm or whatever). Which method is easier depends on your DIY capabilities, or your budget to buy new things.

 

[amberwolf]

Don't sell yourself short. I've chased lots of electrons, but not in bldc controllers. You have far more than I. My follow up was both to see if I was missing something on the concept, but also in the context of John's question. The answer to can dual PR's run a single motor is basically not yet?

The answer is...not as a plug-and-play hookup.

If you're willing to open up the motor as noted in my post above, and do the rewiring, you could at least test multiple controllers on a single motor with many (probably most or even neearly all) motors.

 

[BlueSeas]

OK...I can see what your distinction is between a double wiring in the same motor case vs. two distinct hub motors.

The physics of dissecting the dual wind motor with multiple controllers is above my pay grade. But I will speculate If both were trying to "go forward" would be less of an issue than if one went to "regen" mode in competition with the other. That feels like it could cause big problems unless the controllers were designed with that in mind. But maybe one would just neutralize the other. I haven't a clue.

 

[amberwolf]

There should be no way for one to go into a mode that hte other is not in, if you are literally wiring them in parallel, at least for "dumb" controllers, which don't do anything they're not externally "told" to do.

For advanced controllers, you'd need to ensure you understand the behaviors that the controller's various settings will create, and then ensure you set them all up identically in a way that prevents one from operating differently than the others.

Meaning, if regen is controlled only by throttle input or brake levers, if they're all connected in parallel and set to the same thresholds, all controllers should do the same thing at the same time, and no conflict should occur (presuming electrically separated phase wire sets).

If regen is controlled automatically by each controller independently, then if one senses something different from the other(s), it might respond in a different way, and that isn't a behavior I'd care to try to predict the results of.