Baserunner z9 long throttle delay from stop.(Solved)

[neptronix]

If you want to simulate FW click on show advanced under throttle slider to increase kv in increments. Even then though it doesn't 100% simulate it, more of an idea. Going from 7.9kv of standard wind to around 10kv of fast doesn't simulate FW. It simulates a fast wind motor. With FW your kv might go from 8kv to close to 9kv if even that much. You also have full torque as it doesn't kick in till high speed.

I used to do this, but found it created inaccuracy. When a motor has a different kV in reality, Rmotor, Lmotor values will be very different. You can't accurately recompute that without tearing a motor apart and measuring it's copper lengths and diameter. This also doesn't model what is possible in the real world. I can't give Shengyi a ring and order up a 7.43 turn motor.

Not really the same tune as the thing is your not feeding 80a into a z9 plug safely lol. 55a is the cap without melting and cooking things. Phase current heats the motor so yeah it would perform the same as far as for torque output but the motor would melt almost instantly. The point of the fast wind is to trade off torque for speed, yeah you can just up phase current to make up for it but that makes heat and there is a limit. 55a being that limit. A more appropriate controller for the test would have been a baserunner though only goes up to 52v.

That's why in my comparisons i used a phaserunner instead of a baserunner for the high speed wind to get equivalent output power as your standard wind. No way am i using stock connectors and wires if i run this setup.

The idea that one winding or another produces more torque/speed has never been correct. When you change a winding, you just change the ratio of how many amps vs volts you need to make a given amount of power. Differences in copper fill between two motor windings are the real differentiator and in this particular case i'm only at a 0.5% efficiency disadvantage, which is allright considering the alternative of running very high field weakening. The largest discrepancy i've seen between different windings on any motor is 1.5%.

 

[tnoller5972]

Yeah we are saying the same thing. I said for simulating FW not for different winds. In my experience it's been the best thing to simulate fw. Yes when you change a motors kv through winding that's true but you are temporarily changing it through FW. So just bumping up kv to see how it would respond would be adequate, just imagine slightly higher losses.

In the real world, good luck getting this hub to do what you were originally asking while dumping 80+ phase amps through it. New connectors, lol you'll fry the enamel right off the windings but hey you do you.

I never said that changing a winding changes it actual torque or speed, it changes how it's applied. Yes you need higher amps for same torque but both can output same torque. However to feed it the required amount to do that isn't possible without a complete rewind and rebuild of the hub. Even then I'm not sure. You might as well get a large direct drive for what you are trying to do.

The winding changes where the motor hits peak efficiency.

Good luck!

 

[neptronix]

Also field weakening does cause efficiency loss in motor as stated above but as mentioned that's where it's okay to run some as the sx2 is very efficient to begin with so a small hit isn't so bad. Over do it and it will heat up fast with even with no load.

Well, the majority of the efficiency loss will be in the controller itself due to the higher duty cycle required, i don't think anyone has measured whether the motor itself has reduced efficiency and therefore higher heat. Without any good instrumented tests on the motor side, i prefer to keep it safe and avoid field weakening, or run very little of it.

Anyway, i'm very interested in how we can increase the heat shedding capacity of this motor. If we can add 43W of heat dispersion, we could sustain 35mph, because this motor generally gets more efficient the faster you spin it. It just need some duct tape over it's achilles heel.

 

[tnoller5972]

All you'd have to do for accurate fw is get the speeds for motor off grin put it in custom motor spot, keep all settings the same and slowly increase kv.

 

[neptronix]

In the real world, good luck getting this hub to do what you were originally asking while dumping 80+ phase amps through it. New connectors, lol you'll fry the enamel right off the windings but hey you do you.

A smaller turn count will have a thicker wiring to compensate, leaving the phase wires as the main problem. Not a problem for me as i'd be replacing them. The 0.5% efficiency loss in the high speed winding tells us the power loss will be very small. ( this power loss may be entirely in the phase wires itself, BTW )

You might as well get a large direct drive for what you are trying to do.

The problem with direct drive is that in order to get this same efficiency/torque, you need a 15lbs motor, and you also only see similar efficiency in a very limited range of RPM that's lower than what i plan to travel at on average ( 25mph with the occasional burst to 35mph )

Good luck!

Thanks!

 

[tnoller5972]

Yes faster speed causes higher losses in the motor, as stated before..... It's sending a second phase current perpendicular to normal phase current so reduce field. It has to buck extra voltage for current but not much. Most of the effects of FW will be noticed in heating of the hub as Eddy losses, hysteresis, etc all go up.

 

[neptronix]

All you'd have to do for accurate fw is get the speeds for motor off grin put it in custom motor spot, keep all settings the same and slowly increase kv.

We have to account for the Rmotor and Lmotor value if we adjust the kv though. It will vary significantly and effects the efficiency and power output of the motor if don't have it right. The other problem is, we can't see the additional power the field weakening is producing.

Using a difference in throttle % introduces the lowest amount of variables we don't know into the calculation.

 

[neptronix]

It has to buck extra voltage for current but not much.

Yes, that's why i imagine most of the extra heat is in the controller because the switching rate aka duty cycle of the mosfets have to increase.

Most of the effects of FW will be noticed in heating of the hub as Eddy losses, hysteresis, etc all go up.

To my knowledge, there's no instrumented tests showing that field weakening / phase timing advance produces an efficiency loss at the motor level. Let me know if you've seen one that shows the effect of more power with or without increased duty cycle at the same speed.

Well regardless of that, i hope we can agree it's ideal to not use that feature.

 

[tnoller5972]

Geared hubs suck for shedding heat. Have you looked at the gmac or ezee at all. The sx2 is a great motor but it's not on par with them. It's in between a small g311 and a large ezee/gmac

In grins own words lol

4.6 Field Weakening for Speed Boost
One useful feature of the Phaserunner as a field oriented controller is the ability
to boost the top speed of your motor beyond what is normally possible from your
battery voltage. This is done through the injection of field weakening current that
is perpendicular to the torque producing current.
The exact speed increase for a given field weakening current will depend on the
characteristics of your particular motor, and increasing the speed this way is less
efficient than using a higher voltage pack or a faster motor winding. But for a
speed boost of 15-20%, the additional losses are quite reasonable considering
the gains.
The graph below shows the measured motor RPM (black line) as a function of
the field weakening amps for a large direct drive hub motor. The yellow line is the
no-load current draw, which reflects the amount of extra power lost due to the
field weakening. At 20 amps of field weakening, the motor speed increased from
310 rpm to 380 rpm, while the no load current draw is still just under 3 amps.

I disagree on that as well because if used properly it can let you have the benefits of a slower wind motor with higher speeds. It when you get greedy and put to much to where the negative out weighs the positive.

 

[tnoller5972]

Field weakening doesn't increase power it just moves the no load speed point further up so you can still have power to use without back EMF limiting you like normal.

 

[tnoller5972]

Plenty of data on endless sphere as well

-Field weakening does not raise phase current.
The controller generates a second "signal" on the phase wires which works against the magnetic field of the motor to make it weaker.
With a weaker magnetic field the motor makes more rpm/Volt, but torque is reduced and losses and heat generation get higher.

 

[neptronix]

Geared hubs suck for shedding heat. Have you looked at the gmac or ezee at all. The sx2 is a great motor but it's not on par with them. It's in between a small g311 and a large ezee/gmac

I've ran several MACs and have an Ezee here currently. Ezee's have terrible efficiency in small wheels so the SX2 would be better in my case. Even nice on a 20" wheel

[ grin's documentation block here ]

I disagree on that as well because if used properly it can let you have the benefits of a slower wind motor with higher speeds. It when you get greedy and put to much to where the negative out weighs the positive.

I read that a while ago, and have run the predecessor to field weakening in the past. The efficiency loss is notable, i prefer to run a higher voltage whenever possible.

In this case, i'd be running a little on the fast winding, def within Justin's 'safe zone'

 

[neptronix]

Plenty of data on endless sphere as well

I know, i run the place