What is phase current and what is a good amount for me?

[brumbrum]

I thought i may get a good honest answer here. I have a lipo pack 13s (48-54v) 15ah. i want to use anything from 30 to 45 amps. Controller is a lyens 12 fet Sensorless i have a programming cable and software.
Motor is a rear magic pie that has been rewired with good quality 12AWG wire for sensorless use.

I currently have the phase current at 80 amps. Would i benefit from turning this up for better performance? And what does this parameter actually do?

Cheers

Andrew

 

[NeilP]

Greater phase current give more acceleration/....I think......try various settings and see..up to about 2.5 to 3 times the battery current. so try phase current up to 90 with your battery current set at 30 amps.


I have my 18 FET lyen 4110 set at ..80 or 90 amps battery, cant remember what the phase is set at. I do see peaks of 130 amps battery even with over-current detection set to 0 seconds. See Lyesn sale thread on your controller or else e-mail him direct to see waht max settings he says is good.

 

[gwhy!1]

Hi Andrew,
There is really no right or wrong answer for the amount of phase current limit.. a ball park figure is 2 - 2.5 x battery current, The trick is to get the right balance and the best way ( well my way, and it may not be the best )to do this is to start with around 1.2 x battery current then go out for a ride ( with a watt meter fitted ) and see if the current limit set in the controller is being reached, if the max current is below the set current limit then up the phase current to 1.4 x battery current and so on until the max battery current limit is being reached this will then be your optimum phase current level. The motors and gearing I use this is normally around 1.4x battery current but on a hub motor I would expect this to be a higher level more like 1.8x battery current. You can go a little higher and this will improve the low speed torque but this will very much depend on other factors. I have yet to find any benefit going over around 2.2x battery current on any of the motors/setups that I have played with... but thats not to say that will not benefit all setups..

 

[brumbrum]

Fantastic. Thanks for answering my questions, i really feel i have learned something new and can now play a little with the phase. I have tried 45 amp(battery)and the wattage got no where near where it should and the amps got no further than 40. The acceleration has been very slow, i just thought it was to do with the magic pie winding.
I will also contact E. Lyen for some advice as well. Thanks both for the local knowledge.

 

[gwhy!1]

Fantastic. Thanks for answering my questions, i really feel i have learned something new and can now play a little with the phase. I have tried 45 amp(battery)and the wattage got no where near where it should and the amps got no further than 40. The acceleration has been very slow, i just thought it was to do with the magic pie winding.
I will also contact E. Lyen for some advice as well. Thanks both for the local knowledge.

the current on the watt meter should only go upto the max of what your controller battery current is set for ( maybe +-5A of set current ) , so Im guessing that the 40A that you were seeing is about right. You only really need to do one full throttle launch on the flat to see if the battery current limit is being hit as once you are moving the battery current can creep up to the limit and phase current limit may not come into it. its this standing start current that need to hit the battery current limit of the controller.

 

[brumbrum]

Yep, i totally understand that. I think i will try and raise the phase current by 10 and see if there is any extra 'omph' in the initial acceleration and go from there. I will try both 35 and 40 amp from the battery.

What happens if i go over the 'optimum' phase current, will it just cause heat and no extra power?

 

[gwhy!1]

Yep, i totally understand that. I think i will try and raise the phase current by 10 and see if there is any extra 'omph' in the initial acceleration and go from there. I will try both 35 and 40 amp from the battery.

What happens if i go over the 'optimum' phase current, will it just cause heat and no extra power?

if you go to high with the phase current you could pop your controller if the motor is really chugging and the throttle speed is being dragged down to much, a standard 12fet controller should be ok for around a safe max of around a total of 150A phase current ( can be ok upto around 200A, this depends of the type of fets in the controller and the setup( motor and gearing) ) if I was you I would play it really safe and do no more than 100A phase current. so if your Battery current is 50A set phase current to no more than 150A ( 3x battery current ) or extra safe 50A battery and a phase of 100A ( 2x battery current ). As neil said set the block time down to 0 this will ( should ) limit the current as fast as possible if a over current situation occurs. The optimum settings will just be the less stressful ( but working 100% correct ) settings for the controller.

 

[brumbrum]

Thanks again for the prompt answer. I will tinker with the controller if it is dry tonight :?

Cheers.

 

[d8veh]

I'm still missing something somewhere on this phase current control. All the controller does is open and close the FETs at a particular pulse timing with PWM within the pulses. Right? When you're on full throttle, the controller should give block commutation (no PWM) unless you've exceeded a current limit, when it can revert back to PWM. Does the controller vary the pulse width as well as the PWM within it? If so, how does that relate to phase current control, and how would that work with a sine-wave controller? Or is there a fixed ratio between phase current and battery current, and the controller limits whichever is the highest (considering the ratio) that you've programmed in those two parameters? This has been bugging me for a while!

 

[NeilP]

Can't answer that ..but I thinkg this is wrong:

When you're on full throttle, the controller should give block commutation (no PWM)

I thought it only switched over from PWM once max possible RPM is reached. That is how we get beyond 100% setting. PWM stopps and then timing 'advance' starts, 'moving' the square wave. I am in n way knowledgable about any of this, that was merely my understanding from using Burties timing Adjuster tool

 

[teklektik]

... All the controller does is open and close the FETs at a particular pulse timing with PWM within the pulses. Right? When you're on full throttle, the controller should give block commutation (no PWM) unless you've exceeded a current limit, when it can revert back to PWM. Does the controller vary the pulse width as well as the PWM within it? If so, how does that relate to phase current control, ...? Or is there a fixed ratio between phase current and battery current, and the controller limits whichever is the highest (considering the ratio) that you've programmed in those two parameters?

I thought it only switched over from PWM once max possible RPM is reached.

Although a Xie-Chang (Infineon) controller is aware of the hall commutation period, it has no idea how many poles the motor has and so is unaware of actual motor rpm or what would constitute a max rpm. In broad strokes, it operates by directly mapping the throttle setting to PWM, monitoring battery current to detect built-in and programmed current limit infringements, and eliminating limit violations by altering PWM.

The controller scales the throttle 0-100% across the range of PWM to make the effective voltage applied to the motor vary according to the throttle setting. At 100% throttle, the controller ceases PWM and shifts to block commutation (full 'ON' and slightly trapezoidal waveform). In the magic 'speed' settings to give greater than 100% throttle, the throttle 'PWM range' is scaled a bit lower to cause block commutation to kick in at less than full throttle; above that throttle setting the shape of the pulse is altered to become increasingly square and thus increase the effective delivered motor voltage. There is no PWM timing adjustment. (see this post).

Rated Current is the battery current measured via the shunt, but Phase Current is not measured - it is estimated from the Rated Current and fixed built-in assumptions about motor LR characteristics. The controller reduces motor voltage when either the actual rated or estimated phase current exceeds a programmed or fixed internal 'secondary' limit. Such limiting has the same effect as reducing the actual throttle input and causes a resulting reduction in PWM/block commutation/waveform until the limit infringement is removed.

If WOT is applied on start up, Rated and Phase Current limiting are suspended for the programmed 'Block Time' seconds to allow a high current boost to get the bike rolling. An internal secondary limit is in play for this period but it is so high as to be essentially unlimited.

There's a wealth of posts with myth and mystery about 'throttle over 100%', but I believe the above is an accurate summary of the most contemporary consistent/factual material.

 

[NeilP]

OK, got it..thanks

 

[brumbrum]

Quick update, whilst you lot talk about things that are way over my head i have reprogrammed my controller and now have it set at 95A for phase current and 35A for battery current. The block time has been lowered to 0.2 and the bike is performing much better. The take off is slightly more aggressive but the windings of the magic pie keep things smooth and steady ( a bit boring for me to be honest) i prefer a slower speed and more torque of a geared motor. Anyway, the CA now shows a spike of 44 amps but very quickly reigned in to 35 where it stays as the bike steadily accelerates and then lowers. Much much better than what it was.

I so wish i could get a geared sensorless motor. I suppose they don't exist.

 

[NeilP]

I would have expected more torque from a non geared motor...but I only have only seen and tried low powered geared hub setups..one at 12 s LiPo and one at 14s Lipo. both with 12 FET Controllers.
Compared to my Xlyte DD 5304 running at 20 series with a 18 FET controller at 90 amps batt / 240 phase, both the geared setups are quite gutless. Actually surprised to hear you say geared setups have much torque at all...always though of them as the thing for low power only.

But now I think about it, a geared motor could have much more torque, depending on the gearing..if using strong enough gears

 

[brumbrum]

I am comparing my pie set up to a bafang bpm 500w with a 201 rpm. It has a max speed of about 18mph and is run on a lyen 6fet 25amp with 54v li-ion 18650 home made pack. For off road use the initial acceleration of this will get you up rocky and muddy inclines. The magic pie is robust and sensorless which makes it trustworthy on bumpy ground but the acceleration lacks punch. I think it is a windings issue. I think? :?

 

[d8veh]

... All the controller does is open and close the FETs at a particular pulse timing with PWM within the pulses. Right? When you're on full throttle, the controller should give block commutation (no PWM) unless you've exceeded a current limit, when it can revert back to PWM. Does the controller vary the pulse width as well as the PWM within it? If so, how does that relate to phase current control, ...? Or is there a fixed ratio between phase current and battery current, and the controller limits whichever is the highest (considering the ratio) that you've programmed in those two parameters?

I thought it only switched over from PWM once max possible RPM is reached.

Although a Xie-Chang (Infineon) controller is aware of the hall commutation period, it has no idea how many poles the motor has and so is unaware of actual motor rpm or what would constitute a max rpm. In broad strokes, it operates by directly mapping the throttle setting to PWM, monitoring battery current to detect built-in and programmed current limit infringements, and eliminating limit violations by altering PWM.

The controller scales the throttle 0-100% across the range of PWM to make the effective voltage applied to the motor vary according to the throttle setting. At 100% throttle, the controller ceases PWM and shifts to block commutation (full 'ON' and slightly trapezoidal waveform). In the magic 'speed' settings to give greater than 100% throttle, the throttle 'PWM range' is scaled a bit lower to cause block commutation to kick in at less than full throttle; above that throttle setting the shape of the pulse is altered to become increasingly square and thus increase the effective delivered motor voltage. There is no PWM timing adjustment. (see this post).

Rated Current is the battery current measured via the shunt, but Phase Current is not measured - it is estimated from the Rated Current and fixed built-in assumptions about motor LR characteristics. The controller reduces motor voltage when either the actual rated or estimated phase current exceeds a programmed or fixed internal 'secondary' limit. Such limiting has the same effect as reducing the actual throttle input and causes a resulting reduction in PWM/block commutation/waveform until the limit infringement is removed.

If WOT is applied on start up, Rated and Phase Current limiting are suspended for the programmed 'Block Time' seconds to allow a high current boost to get the bike rolling. An internal secondary limit is in play for this period but it is so high as to be essentially unlimited.

There's a wealth of posts with myth and mystery about 'throttle over 100%', but I believe the above is an accurate summary of the most contemporary consistent/factual material.

Thanks for that, but I still can't figure out if the controller can only limit whichever is the highest out of phase current and battery current, so that it doesn't matter which you use to set the limit. From your explanation, it sounds like the ratio of currents is fixed.

According to the LSDZS knowledge base, speeds above 100% are indeed achieved by changing the timing:
http://www.lsdzs.com/e/newsshow.asp?newsid=138

 

[teklektik]

Thanks for that, but I still can't figure out if the controller can only limit whichever is the highest out of phase current and battery current, so that it doesn't matter which you use to set the limit. From your explanation, it sounds like the ratio of currents is fixed.

According to the LSDZS knowledge base, speeds above 100% are indeed achieved by changing the timing:
http://www.lsdzs.com/e/newsshow.asp?newsid=138

Well, I explained it as best I could, indicating that phase current estimates are ongoing, either rated or phase currents can precipitate limiting, and never mentioning ratios at all. That's it for me - sorry it wasn't useful for you...

As for your controller reference re: timing, I tried to be clear that I was only discussing the Xie-Chang (aka Infineon) controllers that we see from cell_man and Lyen - your reference appears to be for some other type. There is a reference above to a waveform discussion and here's an earlier post - both appear to discount the 'timing' theory although the matter of overlapped phase pulses because of changes in pulse shape might be considered a 'timing' change from a certain point of view. As I indicated, this particular point for Infineon controllers has been the subject of much discussion and I merely gave a best effort recounting and reference... In any case, it's clear that controllers of other types or from other sources may work differently.

 

[100volts+]

The magic pie is robust and sensorless which makes it trustworthy on bumpy ground but the acceleration lacks punch. I think it is a windings issue. I think? :?

I'm pretty new two the game but I do have a sensorless bike and a sensored bike. Low end torque is a sensored bike's forte. No sensorless bike will have great low end torque. My sensorless bike is very trustworthy though.

 

[brumbrum]

The magic pie is robust and sensorless which makes it trustworthy on bumpy ground but the acceleration lacks punch. I think it is a windings issue. I think? :?

I'm pretty new two the game but I do have a sensorless bike and a sensored bike. Low end torque is a sensored bike's forte. No sensorless bike will have great low end torque. My sensorless bike is very trustworthy though.

Actually, i think that is the answer plain and clear That is the sacrifice you make for ditching hall sensors and the crappy thin wires. Thanks It was starring me in the face.

 

[drsolly]

I'm trying to understand this issue, but I've come up against a bit of a block. I'd like to improve my understanding here.

If there's 20 amps at 50 volts leaving the battery, then the battery is supplying 1000 watts.

Conservation of energy means that the motor can't be pulling more than 1000 watts. So if the phase current is, say, 40 amps, then the phase voltage must be 25 volts. Which surely isn't correct. So I thought some more.

These figures are averages. The battery is supplying DC, so that 20 amps and 50 volts is steady. But the motor is using AC, so an average of 20 amps means that it varies equally between 0 amps and 40 amps at 50 volts. The apparent momentary violation of conservation of energy is, I guess, accounted for by capacitors in the controller?

But then I remember that there's three phases, and the "phase current" is, I'm guessing, the total of the three. So I'm back to not understanding how phase current can be greater than battery current, because although each phase is sine-waving, the total of all three isn't,.

Is my understanding here on the right track? Perhaps someone could put this more clearly for me?

 

[Punx0r]

Someone else explained it to me as: the controller operates like a buck converter - it can trade voltage for current or vice-versa. So if the motor is heavily loaded, but turning slowly, voltage required is low (as back EMF is also low), so some of it can be "traded" for current. Power remains the same.

That, at least, is my casual understanding of the battery-phase current relationship.

 

[NeilP]

If there's 20 amps at 50 volts leaving the battery, then the battery is supplying 1000 watts.

So due to losses, you will get LESS at the wheel

, then the phase voltage must be 25 volts. Which surely isn't correct.

Not sure..as PunxOr says..maybe some buck boost conversion going on ..that I do not know..but I always assumed that the motor voltage stayed the same or less than battery voltage.

So I thought some more.

Be very careful doing that..it is a very dangerous path to go down :lol:

These figures are averages. The battery is supplying DC, so that 20 amps and 50 volts is steady.

Over a longish time period, but I am guessing that if you scoped the input , with throttle held steady, you would see some 'ripple' o the input too

But the motor is using AC,

No, Not AC...effectively AC , yes, but it is actually square wave pulsed DC. There is no negative going voltage. The there is Pulse width modulation (PWM). Which I know nothing about.

From what I have seen ...imagine a square wave... Zero volts being...well zero volts...and the top of the square wave being max battery voltage (less FET junction voltage drop) .

So you have your square wave...each individual 'ON' part of the square wave is not actually a solid 'ON'...but a series of much smaller square wave pulses within the 'bigger square wave'. The length of the smaller "ON" pulses, in relation to the OFF' pulses" within the bigger pulses is determined by throttle position

. The apparent momentary violation of conservation of energy is, I guess, accounted for by capacitors in the controller?

Those pesky caps have a lt to answer for!!

From my understanding, when the FET's are OFF (so no conduction from the battery) current within the coils still flows..induced from movement of the magnets...like electrical inertia ( I forget the correct term) .
This current has to go somewhere...so it goes in to the caps..this stored charge is then released at the next on cycle

But then I remember that there's three phases, and the "phase current" is, I'm guessing, the total of the three.

Not got my head around that myself but I think not...The 'extra' phase current coming from the stored charge within the caps

So I'm back to not understanding how phase current can be greater than battery current, because although each phase is sine-waving, the total of all three isn't,.
Is my understanding here on the right track? Perhaps someone could put this more clearly for me?

Again......not Sine wave...square wave....unless of course I have stumbled on to a thread for a sine wave controller and I have just blindly started typing.

Phase current greater than battery current due those pesky capacitors.







Then you get to the complicated issue of programming the controller to up to speeds greater than 100%. (120% max from software I have seen)

From what I gather...100% is where all the little pulses within the big square waves go from being little on/off pulses to fully ON for the whole period of the "big" square wave. Controller switches from PWM to _________ Commutation ...(Insert correct techy word in the blank).




I could off course been talking a load of utter bollocks for the last few mins...but it is the best I can give..it is how I have managed to understand it over the past few years

 

[gwhy!1]

ok, one way to think of it is that when the coils are not energized ( being driven by the controller ) the other coils are acting as a generator and this is ac. there is also the induced voltage in the active coil from when the fets switch off which is a negitive spike of voltage of a amplitude determind by the inductance of the coils, volage across the coil, switching speed of the fet and frequency of the fets at which they are chopping the voltage PWM, so you have a lot of additional voltages going on that the controller ( fets ) needs to keep under raps and all this add up to the phase currents, if you have a motor that is for example 100kv and spin it in a drill at 5000rpm then you will be generating 50vac on each of the phases of the motor now if you short out one of these phases that generated voltage gets dumped into the resistance of the winding and this in very simple terms makes very high currents as the resistance of a winding may be only 0.1ohm . This is very simple terms , but it will give you some idea of where this extra voltage and current can come from.

 

[drsolly]

Ah. Yes, square not sine, I knew that, but I hadn't known that the volts doesn't go negative, thanks for that. All knowledge might help one day.

I'd also like to explain the following.

I'm using a sensorless Infineon controller (because bike.3 has a sensorless motor). When I go from speed 1 (which I've set at 50%) to speed 2 (set at 100%), the wheel spins *much much* faster. But when I go to 120 % (speed 3), there's no change.

Is this because I'm sensorless? Or is it because I'm programmed the Infineon wrongly?

 

[NeilP]

Possibly because something else is limiting max speed at a guess.

Do you have cycle analyst or perhaps artificially low current settings ?