wye - Delta -> differences and stereotypes

[spinningmagnets]

I don't know why Thud likes Wye for his race motor instead of Delta, but...he has built and raced many different motor combinations.

"Re-wind of a turnigy 80/100 (Now-tutorial w/Video)" (Thud, 17 pages)
https://endless-sphere.com/forums/viewtopic.php?f=30&t=20618

So far, I haven't built a better motor & controller set up than the 6-turn, 2-in hand, 14G, dlrk/wye terminated motor...run the thing with a 12 or 18-FET xie-chang with a 6-Kw limit on 20S LiPo cells & you will not find a better RC power combination [with external hall sensors].

Controller settings:
Use Xpd in the tech section to flash settings
Do not solder the shunt (& throw all the calibration out the window)
Do the math with your voltage to arrive @ 6kw @ use that for battery amps.
Set the phase current conservatively (start with battery amps) & make small increases untill your happy with your accelleration, or the controller starts to show some heat.
Most importantly set the block time to zero.

This method has been tested on the race track & in the neighborhoods....you can drain a 25ah pack without overheating controllers or motors from my experience.

 

[amberwolf]

I don't know why Thud likes Wye for his race motor instead of Delta, but...he has built and raced many different motor combinations.

For the RC motors, it's probably because it increases the inductance the controller sees, so it is less likely to blow them up on a start from a stop.

At least, that's the reason I recall from the various threads about such things at the time the Death Race stuff was still going on. Could be misremembering.

 

[Lebowski]

I side with John in CR, with the addition that WYE is better when taking 3rd order harmonics into account... (See my 'always wind in wye' thread)

 

[spinningmagnets]

I am sure that I will miss some important factor, because I really don't understand this. However, Thuds motors were 80mm diameter outrunners, and he was using them in a race...meaning that there was only one start, and he spent the entire time at (or near) full throttle. He specifically built a robust 2-speed mechanical transmission to give himself more low-speed system options.

Thanks Amberwolf, I had forgotten about inductance (or as I call it "voodoo")

 

[ElectricGod]

I side with John in CR, with the addition that WYE is better when taking 3rd order harmonics into account... (See my 'always wind in wye' thread)

Would this effect current draw dramatically?

I've tried the big block I have on two differnt controllers now and they both elicit the same results. Getting the halls and phases right is pretty simple. As I stated earlier in this thread, I would try again on the hall placement to be sure they were not wrong. I also eliminated the wye/delta relay and since all the phase ends terminate in male 5.5 bullets, it was super easy to make up several 3-way female bullets to connect up the phases either in WYE or delta. Obviously the start and end of each wind matters so when I first pulled them out of the motor which was originally WYE I labeled all the starts as B2, Y2 and G2. All the ends that originally came out of the motor are B1, Y1 and G1. So in my latest test for delta, B1 connected to Y2, G1 to B2, Y1 to B2. Since I didn't care about motor direction, just current draw, I arbitrarily connected the controller phases to the third bullet in each set of 3 bullets.

Possible hall combinations are as follows. I think I said 9 earlier, but obviously there are only 6. Of which only 2 will run the motor and 1 of those 2 will draw lots more current than the other.
YGB
YBG
GYB
GBY
BGY
BYG

I tried all 6 combinations on two different controllers while trying this motor in delta and found the "low current" combination was about 3X more battery current than I got for the same motor configured in WYE where Y2,G2 and B2 are connected together. Again, I checked to be sure I had the low current hall combination. How do I explain this? I tried all possible hall combinations to find the two that would run the motor and then picked the low current combination. The motor ran all the way to WOT, but it drank current at 3X what it did in WYE. I have no problem with being wrong, but I seriously doubt I made any mistakes at this point. This isn't exactly rocket science. Anyone with some basic understanding of WYE and delta and how to connect up the halls ought to be able to get it right. Anyway, I stand behind my observations while trying this motor in delta..3X battery current draw while in delta over what I would see in WYE. The other thing I noticed is that the motor in WYE, barely warms up when running at WOT. In delta, even with the "low current" hall combination, the motor gets hot quite quickly. I'm no motor physics expert so I don't understand why that's happening, but it sure seems related to delta and the 3X battery current draw to me. The Grintech controller I was originally testing on was running at 48 and 82 volts. So on the second controller which runs up to 150 volts, I tested the motor at 48 and 82 volts and also at 148 volts (36S). Same behavior...in WYE I drew far less current than I did in delta...regardless of the battery voltage. I didn't bother running the motor at WOT in delta at 148 volts, it got so warm at no load at 82 volts and WOT, what was the point? In WYE at 148 volts and WOT the motor got warmer than it did at 48 or 82 volts, but never too hot to touch like it did in delta at any voltage.

I believe what you guys are saying, but my observations just don't fit. That's what I was trying to show Poxn0r. What people say should happen and what I observe are not matching up.

I haven't measured the lams, but they look like .3mm to me and the individual wire strands look like 26awg to me.

 

[silence]

As mentioned many times in this thread, a motor designed to run in wye may require a different hall placement when switched to delta.
Physical re-positioning, not playing with combinations.
For exaple - if they are located between stator teeth right now, they may need to be placed in the center of the tooth or vice versa.
Otherwise all the working combinations can be either too advanced or too retarded, leading to high no-load current and excessive heat.

Taking 3x more current to get the motor turning doesn't sound right to me either. Something else must be going on.

Yes, in most cases you need to re-position the hall sensors when switching from delta to wye. If you used a sensorless controller,
you would not have this issue. This could explain the 3x higher current. It would be great to test the motor delta vs. wye using a sensorless controller.

Something seriously amiss, recirculating currents or inappropriate hall sensor placement for delta configuration comes to mind. You will find threads somewhere on ES
where hall sensor placement had to be changed for successful wye/delta switching to work.

... ended up running the motor with grossly miss-timed halls

Hall position is calculated by the controller normally 120°or 60° programable or self learn, The halls are situated in between phases for even number pole counts like the big block
rather than in the centre of a phase for an uneven pole count, the circuit board with the halls floats in between the phases so if they are off just a fraction it will retard or advanced
a phase, when switching to delta it maybe exaggerating this effect with increased hysteresis in the laminations from the added inductivity creating a larger emf

 

[ElectricGod]

As mentioned many times in this thread, a motor designed to run in wye may require a different hall placement when switched to delta.
Physical re-positioning, not playing with combinations.
For exaple - if they are located between stator teeth right now, they may need to be placed in the center of the tooth or vice versa.
Otherwise all the working combinations can be either too advanced or too retarded, leading to high no-load current and excessive heat.

Taking 3x more current to get the motor turning doesn't sound right to me either. Something else must be going on.

Yes, in most cases you need to re-position the hall sensors when switching from delta to wye. If you used a sensorless controller,
you would not have this issue. This could explain the 3x higher current. It would be great to test the motor delta vs. wye using a sensorless controller.

Something seriously amiss, recirculating currents or inappropriate hall sensor placement for delta configuration comes to mind. You will find threads somewhere on ES
where hall sensor placement had to be changed for successful wye/delta switching to work.

... ended up running the motor with grossly miss-timed halls

Hall position is calculated by the controller normally 120°or 60° programable or self learn, The halls are situated in between phases for even number pole counts like the big block
rather than in the centre of a phase for an uneven pole count, the circuit board with the halls floats in between the phases so if they are off just a fraction it will retard or advanced
a phase, when switching to delta it maybe exaggerating this effect with increased hysteresis in the laminations from the added inductivity creating a larger emf

Physical re-positioning for delta? I read those posts and thought thye meant I had the wrong hall/phase combination since I knew the halls were fixed between the teeth. I guess I should have posted that the halls are fixed between the teeth. My understanding is that WYE or delta didn't matter. What mattered was if the hall was centered between the stator teeth or in the center of the stator tooth. For a motor with even numbers of stator teeth, the halls are between the stator teeth, for odd numbers of stator teeth the halls sit in the center of the teeth. Physically placing the halls at 120 degrees apart or 60 degrees apart does not matter as long as they are electrically 120 or 60 degrees apart. AS you can see in the below pictures the halls are right next to each other. I know this motor uses 120 degree placement and yet those halls are physically just a few degrees apart. Is this hall placement information correct or not?

The halls in these motors fit into small slots in between the stator teeth. It's virtually impossible for them to be in the wrong place. The first picture is from this exact motor and the other two are from the other big block I purchased a year+ ago. Sorry for the dark picture, I wasn't taking a picture of the halls, but rather the phase ends so the halls were under exposed. you can see despite the pic being dark that the halls are between the teeth. Both motors are identical in this regard...the halls fit into small slots between the stator teeth and the motor has an even number (12) of teeth.

Regarding retarding or advancing...is that specific to some motors and not others? I have two alien power outrunners with even tooth counts (c80100 and 12090) and they both have the halls dead center between the stator teeth and they are both wired delta. Anyway, advancing or retarding the halls in my motor doesn't sound like it's the problem...if what I thought I knew about hall placement is in fact correct. I've read about advancing or retarding halls, but didn't see any point when the best spot was between the teeth or centered over the teeth...depending on the stator count.

This is a BOMA inrunner with odd (9) stator teeth and as expected the halls are centered in the middle of the teeth. It is wired WYE.

This is my 12090. Halls are centered between the teeth and it is delta with even stator count. It seems to me that advancing or retarding the halls is a red herring, but I'll try anything.

 

[liveforphysics]

A properly designed motor can only be designed for either Delta or Wye, not both, with respect to keeping its BEMF sinus and low harmonic content. If you spin your motor while scoping it's BEMF and it looks sinus, then you know if you were to change its winding termination, it would have spikey harmonic content laden BEMF that would create poor motor performance.

A Wye motor vs a Delta motor of the same Kv has no ultimate torque difference or torque per amp difference.

Delta windings invite the potential for added losses from winding circulation currents.

Delta is used for toy motors because it avoids a manufacturing step of making a Wye termination.

Run the termination your motor was designed to have low harmonic BEMF with. If your motor wasn't designed to optimize BEMF, then it may or may not matter what winding termination you use, and a better option would be switching to a motor that was actually optimized.

 

[ElectricGod]

A properly designed motor can only be designed for either Delta or Wye, not both, with respect to keeping its BEMF sinus and low harmonic content. If you spin your motor while scoping it's BEMF and it looks sinus, then you know if you were to change its winding termination, it would have spikey harmonic content laden BEMF that would create poor motor performance.

A Wye motor vs a Delta motor of the same Kv has no ultimate torque difference or torque per amp difference.

Delta windings invite the potential for added losses from winding circulation currents.

Delta is used for toy motors because it avoids a manufacturing step of making a Wye termination.

Run the termination your motor was designed to have low harmonic BEMF with. If your motor wasn't designed to optimize BEMF, then it may or may not matter what winding termination you use, and a better option would be switching to a motor that was actually optimized.

I've read about BEMF some, but never put any serious research into it or it's implications. Yeah...new thing to look into!!! Would BEMF cause a motor optimized for WYE to draw excessive amounts of current even with the correct hall placement and correct hall/phase combination? If so, well then, that's the answer and why this wont work. This I did not know about or even consider it a possible issue...if that's true.

LOL...toy motors...so an 18kw 12090 is a toy motor? But yes...I understood what you meant...small outrunners that are super cheap.

 

[Ianhill]

LOL...toy motors...so an 18kw 12090 is a toy motor? But yes...I understood what you meant...small outrunners that are super cheap.

I think he meant toy motors as in toy rc cars and high speed cd drives etc rather than 18kw is a toy.

Here's a nice read on bmf, I got a few sections in different txt books I need to get a read through again refresh the lingo but I have nothing on how the controllers work other than Internet.

https://www.digikey.co.uk/en/articles/techzone/2013/jun/controlling-sensorless-bldc-motors-via-back-emf

And a bit on cd drives.

http://www.ziva-vatra.com/index.php?aid=26&id=rwxly3ryb25py3m=

 

[liveforphysics]

If the motor was built to be optimized in Wye, it will run like crap in Delta and make lots of heat. (No matter where your halls are timed)

If the motor was designed to be optimized in Delta, terminating it in Wye will result in poor performance. (No matter where your halls are timed)

If a Delta/wye switch works well for your motor, then your motor is unoptimized rubbish (like most Ebike and hobby grade motors).

 

[John in CR]

Thanks for that interesting input LFP. I always wondered why the factory went with series/parallel switching on their high efficiency 2 speed hubbies instead of Delta/WYE, which would have been easier to mechanically switch in the motor.

 

[ElectricGod]

If the motor was built to be optimized in Wye, it will run like crap in Delta and make lots of heat. (No matter where your halls are timed)

If the motor was designed to be optimized in Delta, terminating it in Wye will result in poor performance. (No matter where your halls are timed)

If a Delta/wye switch works well for your motor, then your motor is unoptimized rubbish (like most Ebike and hobby grade motors).

Thanks Luke...

You confirmed everything I am seeing and why. Thanks so much for your input and for confirming that hall placement wasn't the issue. That's what I thought despite people saying otherwise. Now I would say this thread has served it's purpose. I unwittingly proved that a motor that runs well in WYE is crap in delta. I also feel exonerated that physical hall placement if correct is always correct wye or delta. It was suggested that hall/phase combinations changed when you switch from wye to delta. I think that is also false if the phase ends are connected correctly. In my case, with or without the relay in place, I saw the exact same behavior (3X more current draw in delta) with the same hall setup as WYE or in trying to find a "better" combination. It didn't make a difference. IE: reordering the halls for delta was not the issue. People who have experienced the need to reorder their halls when they switch from WYE to delta have had to do so because their phase ends were not connected correctly. I did not have this issue. My motor as seen in my wye/delta videos ran with the same hall combination before and after the switch over. I already had the optimal hall/phase combination.

This is one of those times where Luke swoops in...red cape flapping in the wind behind him while singing in a baritone voice "Here I come to save the day!!!"

 

[ElectricGod]

LOL...toy motors...so an 18kw 12090 is a toy motor? But yes...I understood what you meant...small outrunners that are super cheap.

I think he meant toy motors as in toy rc cars and high speed cd drives etc rather than 18kw is a toy.

Here's a nice read on bmf, I got a few sections in different txt books I need to get a read through again refresh the lingo but I have nothing on how the controllers work other than Internet.

https://www.digikey.co.uk/en/articles/techzone/2013/jun/controlling-sensorless-bldc-motors-via-back-emf

And a bit on cd drives.

http://www.ziva-vatra.com/index.php?aid=26&id=rwxly3ryb25py3m=

Thanks Ian...I'm sure I will learn something in these links...lots of things.

 

[liveforphysics]

Getting hall timing right is still critical, has a major effect on motor heating, and some motor designs will shift neutral timing location when delta-wye termination change is made.

I was merely saying, if the motor was designed for Delta and you Wye terminate it (or visa-versa), it doesn't matter so much that you can correct the hall timing if the motors BEMF waveform is compromised terribly (as it would be in an optimized motor).

 

[fechter]

I'm trying to understand why this is true. It seems like there should be some motor configurations that would work in either delta or wye. From what I've gathered, changing from delta to wye (or the reverse) is commonly done with large 3 phase induction motors. For a PM motor, using a sensorless controller would eliminate any hall timing issues.

 

[spinningmagnets]

I now wonder if induction motors (common in industry) use halls. I'm thinking probably not. They run at a fairly constant RPM. They are stationary mounts sooo...sensorless should be fine?

 

[Ianhill]

I now wonder if induction motors (common in industry) use halls. I'm thinking probably not. They run at a fairly constant RPM. They are stationary mounts sooo...sensorless should be fine?

I suppose any motor with a start and run winding is optimised for the delta run wind so the power factor is as close to 1 as possible for most of its run time but a centrfugal switched in wind is not the only way of introducing resistance at start up.

When current lags the voltage power factor will drop, the further they separate the bigger the bill the power company's will send you so they tend to use capacitance to keep them close as possible for most of the motors run time so when it's reached its designited rpm the power factor is around 0.9 or better.

I've never seen any industrial induction motor with halls, but there's lots of ways of driving them this article explains differing methods one may come across.
http://www.electrical4u.com/induction-motor-drives-starting-braking-speed-control-of-induction-motor/

Thinking about a centrfugal switched in delta wind and it seems that it could very easy operate inefficient with wear of the switching mech, but an auto transformer etc would need less maintenence to ensure its switching over at the desirable time, I suppose when your running hundreds of these things at a mill etc you need them all chooching bang on or it can be thousands of pounds lost a day.

Thinking again about inductivity and it seems to me that the caps on a bldc controller could be limiting the power factor available to a motor, so your cap size will limit the amount of inductance you can efficiently run and even though a controller may start the motor the current will lag and we will see the 3 to 9amps or 3× magnitude rather than 1.7× in comparison between the delta and wye wind switch the controller is beyond its inductive limits and it's becoming inefficent the power factor is dropping to like 0.5 or so as well as motor losses it's just a massive waste of energy specially on a battery system.

 

[ElectricGod]

I now wonder if induction motors (common in industry) use halls. I'm thinking probably not. They run at a fairly constant RPM. They are stationary mounts sooo...sensorless should be fine?

Thinking again about inductivity and it seems to me that the caps on a bldc controller could be limiting the power factor available to a motor, so your cap size will limit the amount of inductance you can efficiently run and even though a controller may start the motor the current will lag and we will see the 3 to 9amps or 3× magnitude rather than 1.7× in comparison between the delta and wye wind switch the controller is beyond its inductive limits and it's becoming inefficent the power factor is dropping to like 0.5 or so as well as motor losses it's just a massive waste of energy specially on a battery system.

What caps in a BLDC motor? There's only the filter caps on the power buss's inside the controller. Are you suggesting adding some like run caps are used in an AC motor? If so, then one per phase. and that could be used to get current and voltage close to being in sync again.

 

[Ianhill]

I'm wrong on this one big time, looking at the sensorless drive it uses the undriven phase to compare from, so any caps in line with a phase will go bang with reverse current and make it lose timing.
I don't know enough about the controllers workings to know what I'm saying so other than the motors I'm out of my depth I've seen caps on input sides and that makes sense now I'm still a learning pup even though im nearly 32, domestic and industrial instalation engineer is my qual and it shows lol.

 

[spinningmagnets]

I am certain Wye/Delta switched industrial induction motors start in Wye due to the lower currents, which allow lower-amp rated components all along the line. I was also told that is why heavy duty motors (on air-compressors and other large devices) are using 220V and 440V...to keep the amps down.

 

[Ianhill]

Starting in delta will give a terrible power factor for a high speed high torque motor so its cheaper on electricity and components to use the switching method with motors that are direct to the mains and need to get to a high speed.

It's down to the end goal low speed high torque choose wye
High speed low torque choose delta
High speed high torque you need to start in wye or the grid will flip out and peoples lights will flicker.

 

[ElectricGod]

Getting hall timing right is still critical, has a major effect on motor heating, and some motor designs will shift neutral timing location when delta-wye termination change is made.

I was merely saying, if the motor was designed for Delta and you Wye terminate it (or visa-versa), it doesn't matter so much that you can correct the hall timing if the motors BEMF waveform is compromised terribly (as it would be in an optimized motor).

I agree getting the halls in the right places is important, but there's no difference wye or delta for that hall placement.

How does one "optimize a motor" for WYE or delta? Please give me some articles to read on this subject.

Thanks

 

[amberwolf]

I don't know if it helps, but there's some info here
https://endless-sphere.com/forums/viewtopic.php?f=28&t=15344#p254773
about overlapping poles not working in delta very well; perhaps this is part of that "optimization" for wye?

 

[Rube]

Now I would say this thread has served it's purpose.

This thread uncovered potential for knowledge sharing about relationships between motor termination, timing control and motor construction. Recently I learn't about SIN-COS controllers options and I'd be super keen for a ES 'master class' on the evolution of motor control and timing.

My hobbyist knowledge falls into the category below but thanks to ES'contributors I've learn't from a debate'that began with EG's experiments.

I'm wrong on this one big time...