DIY 10awg phase leads through axle in 9C hubmotor.
- Thread starter liveforphysics
- Start date
liveforphysics
100 TW
EVan said:
Yep. I came to this realization a couple weeks ago. I had previously been viewing the roll of the motor as just "load" when viewing the battery-controller-motor system. It actually is a giant inductor, and any voltage-current input combo from the controller will work out to give the same phase current on both the motor and the controller FETs. I had not realized this before a roughly a month ago. It does not bode-well for everyone doing the HV controllers and not matching them to very high turn-count motors.
ZapPat
10 kW
liveforphysics said:Yep. I came to this realization a couple weeks ago. I had previously been viewing the roll of the motor as just "load" when viewing the battery-controller-motor system. It actually is a giant inductor, and any voltage-current input combo from the controller will work out to give the same phase current on both the motor and the controller FETs. I had not realized this before a roughly a month ago. It does not bode-well for everyone doing the HV controllers and not matching them to very high turn-count motors.EVan said:
This wouldn't be so much of a problem for these ebike controllers if they had lower switching losses (meaning if the FETs would switch faster, they would spend less time in the energy-burning transition period between being fully on and fully off). But these common ebike controllers are not made to be super-efficient PWM converters, they are mostly designed to be used at full throttle at cruise speeds when no PWM goes on at all, only slow commutation events.
This might explain why so many people on ES still relate motor heat to system power (watts), when in reality it's mostly motor/phase current that produces motor heat no matter what voltage your battery is. I made a couple posts trying to discuss this here and here in the air cooling thread... anyone have thoughts about this subject?
Pat
liveforphysics
100 TW
This effect is completely different from switching losses my friend, and would happen just the same of the FETs switched a perfect square wave. Conduction transition losses are also a source of heating, along with energy clamped by the intrensic diode in the FET body from kick-back, but this is a totally different effect.
This effect is current multiplying by PWM.
As a crude example: Have 2 motors, to make the math easy, say one is a x5306, and the other an x5303.
They are both at a speed at which the controller is still in its current limiting stage with identical controllers, and both controllers are drawing say 50v and 50amps from the battery.
In this situation, the x5303 motor has 2x the phase current, and the FETs in the controller are handling 2x the current of the x5306 motor.
Both motors have identical copper fill (24 pieces), so both motors should be making roughly identical heat in this situation, but the controller driving the x5303 will be making roughly double the heat.
This effect is current multiplying by PWM.
As a crude example: Have 2 motors, to make the math easy, say one is a x5306, and the other an x5303.
They are both at a speed at which the controller is still in its current limiting stage with identical controllers, and both controllers are drawing say 50v and 50amps from the battery.
In this situation, the x5303 motor has 2x the phase current, and the FETs in the controller are handling 2x the current of the x5306 motor.
Both motors have identical copper fill (24 pieces), so both motors should be making roughly identical heat in this situation, but the controller driving the x5303 will be making roughly double the heat.
rkosiorek
100 kW
liveforphysics,
but isn't there also some point in the RPM range where due to the 2X higher BEMF the 5306 starts to draw more current than the 5303? at that RPM the BEMF would be limiting the RPM of the 5306 while the 5303 still has more RPM to go. at that point would not the 5303 controller be making the same heat?
rick
but isn't there also some point in the RPM range where due to the 2X higher BEMF the 5306 starts to draw more current than the 5303? at that RPM the BEMF would be limiting the RPM of the 5306 while the 5303 still has more RPM to go. at that point would not the 5303 controller be making the same heat?
rick
SilverSurfer
100 W
liveforphysics said:spinningmagnets said:
That was my original plan. Mentioned earlier in the thread, the bearing recess in the side cover didn't have enough meat in it to open it up further and stuff a bigger bearing inside. I could have stepped up 1 size of ID on the bearing and made a custom bushing, but it wouldn't have much more area than the center of the axle hole with the limited ability to increase the ID of the bearing without increaseing the OD.
These options are of course possible, and you could make a custom side plate for the motor and put a huge bearing in there and run as large of phase wires and water cooling lines or whatever the heck you wanted to run through there.
However, this took about 45mins of time, about $3 in materials, and it's got phase leads that will stay as cool as can be and handle all the current they will need, so it's mission accomplished IMO.
this little snippet of conversation is pretty neat! I dont know yet if any you guys have gone anywhere with this, but Im hooked on the idea! I just bought this flanged bearing pillow block. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280263513351
Thats a 2 1/4" bore~! I will be running some fat booty cables delta AND wye! LOL Thanks for the inspiration! SS
This is a great mod by the way livefor!
I don't know if it's been mentioned but another option would be several strands of transformer wire (enameled, like the windings). More enamel used to "glue" them in place in the spindle.
Virtually no space is then "wasted" on insulation, the sections aren't conformed to a circle (with wasted gaps between) and this should be less likely to melt or chafe or corrode. Any heat is conducted away from the wires, again like the motor windings.
Termination to the flexible cable is then made after the right-angle bend.
I think your way is probably simpler and easier though
I don't know if it's been mentioned but another option would be several strands of transformer wire (enameled, like the windings). More enamel used to "glue" them in place in the spindle.
Virtually no space is then "wasted" on insulation, the sections aren't conformed to a circle (with wasted gaps between) and this should be less likely to melt or chafe or corrode. Any heat is conducted away from the wires, again like the motor windings.
Termination to the flexible cable is then made after the right-angle bend.
I think your way is probably simpler and easier though
John in CR
100 TW
Hold the presses Luke and Pat, because I'm not getting this.
Are you saying that a higher pack voltage doesn't give us a higher voltage in the pulses coming out of the controller?
Even if true I can live with that, because as part of my strategy I'm lowering the effective gearing to increase torque.
The part I really don't get is what you meant by "It does not bode-well for everyone doing the HV controllers and not matching them to very high turn-count motors." With the same current draw from the battery during current limiting why would the lower turn count motor get double the current? Why isn't the phase current limited to the same for both as determined by the controller settings? If it's because of the lower winding resistance, I understand, but I don't understand how the draw from the battery can be the same with double the phase current. At higher rpm where the high turn count motor isn't current limited, then a difference makes sense.
If you're talking only about the speed wind motor being harder on the controller, then I understand that, since the motor can accept more current and the current limiting goes on to higher a higher rpm due to the lower BEMF at any given rpm.
My plan to reduce the controller stress is to tune my HV controllers down from the wide open current settings we had using the Methods controller when you were here. For the speed run bike, I'm going to use the same diameter wheels as you and I rode, but use front and rear motors, so half the load should reduce system stress and still have more torque off the line though speed is the goal. For a single motor and high voltage, my plan is to gear the motor down for about the same top speed as now, but greatly increased torque.
My goal isn't necessarily to get more power into the motor at the lower rpms, but instead to extend the rpm range of high power. eg While the high turn motor is petering out due to BEMF limiting the current, my motor is able to extend that current and torque to much higher rpms, making more power in the same manner the higher Kv RC motors do.
It does sound that in the interest of protecting my HV controllers, I may need to set the phase current multiplier limit to a lower setting than the norm. I wish there was a way to suck out the setting of my stock 15 fet Infineons, because they have been bulletproof with these motors, but there's obviously something tuned quite differently in them that we can probably learn from.
This discussion needs it's own thread, because what really goes on with the controllers and how they react to different motors is very important.
John
Are you saying that a higher pack voltage doesn't give us a higher voltage in the pulses coming out of the controller?
Even if true I can live with that, because as part of my strategy I'm lowering the effective gearing to increase torque.
The part I really don't get is what you meant by "It does not bode-well for everyone doing the HV controllers and not matching them to very high turn-count motors." With the same current draw from the battery during current limiting why would the lower turn count motor get double the current? Why isn't the phase current limited to the same for both as determined by the controller settings? If it's because of the lower winding resistance, I understand, but I don't understand how the draw from the battery can be the same with double the phase current. At higher rpm where the high turn count motor isn't current limited, then a difference makes sense.
If you're talking only about the speed wind motor being harder on the controller, then I understand that, since the motor can accept more current and the current limiting goes on to higher a higher rpm due to the lower BEMF at any given rpm.
My plan to reduce the controller stress is to tune my HV controllers down from the wide open current settings we had using the Methods controller when you were here. For the speed run bike, I'm going to use the same diameter wheels as you and I rode, but use front and rear motors, so half the load should reduce system stress and still have more torque off the line though speed is the goal. For a single motor and high voltage, my plan is to gear the motor down for about the same top speed as now, but greatly increased torque.
My goal isn't necessarily to get more power into the motor at the lower rpms, but instead to extend the rpm range of high power. eg While the high turn motor is petering out due to BEMF limiting the current, my motor is able to extend that current and torque to much higher rpms, making more power in the same manner the higher Kv RC motors do.
It does sound that in the interest of protecting my HV controllers, I may need to set the phase current multiplier limit to a lower setting than the norm. I wish there was a way to suck out the setting of my stock 15 fet Infineons, because they have been bulletproof with these motors, but there's obviously something tuned quite differently in them that we can probably learn from.
This discussion needs it's own thread, because what really goes on with the controllers and how they react to different motors is very important.
John
ZapPat
10 kW
liveforphysics said:
Sorry Luke, for some reason I was thinking of the *motor* heat generation issue instead of the *controller* heat generation issue you were talking about!
You can see the two posts I linked to above were about motor heat, confused me. But I nonetheless would like anyone's thoughts on this subject too...You are of course right about a x5303 being harder on the controller than a x5306, but I think it's actually quite a bit more than just twice the heat for twice the phase current. Conduction losses are I^2*R, so doubling the current in the fets means quadrupling the conduction generated heat, no? Switching heat will be a tad more than double because the fets will switch a bit slower with the higher currents. The quadrupled conduction heat is actually an optimistic figure since the FET's resistance rises with heat, which ends up generating more heat than anticipated (I made an excel spreadsheet for myself a while back to illustrate this effect).
I have discussed this same issue a number of times on a few threads here, once many months ago with methods as I recall. We both got interested in 6X10's (2810) 9C hubs instead of the 9X7/10X6's (2807/2806) that are popular for low voltage battery systems. The slow wound 6X10's are good at high voltages if you don't want super high cruising speeds while at WOT, since they have less phase wire heating issues and cause less controller stress/heat than running a 10X6 at the same speed with part throttle (or with a programmed speed limit).
Pat
John in CR
100 TW
How can a 6x10 possibly have less phase wire heating issues for a given power? The have a longer length of smaller gauge. Same current through a smaller and longer wire means far more heat. If the answer is less current, that means less power.
ZapPat
10 kW
They produce more torque per ampere, and make up for the difference in voltage instead. The end result is the same power, but less phase wire heating.John in CR said:
John in CR said:
The heating is current squared x resistance. If you have half the current and twice the resistance in a "slower wound" motor, at twice the voltage, then you are producing half the heat for the same power.
If you were building a bike with efficiency foremost in mind then a slower winding and higher voltage pack could be a sensible design choice.
I suspect one turn here or there doesn't make a dramatic difference in practice though, and there are usually far greater gains to be made in terms of rolling resistance and air resistance before the motor resistance is worth optimising.
liveforphysics said:EVan said:
Yep. I came to this realization a couple weeks ago. I had previously been viewing the roll of the motor as just "load" when viewing the battery-controller-motor system. It actually is a giant inductor, and any voltage-current input combo from the controller will work out to give the same phase current on both the motor and the controller FETs. I had not realized this before a roughly a month ago. It does not bode-well for everyone doing the HV controllers and not matching them to very high turn-count motors.
Well, maybe, maybe not. It depends on what you're aiming for.
A high pack voltage, a larger controller capable of huge phase currents and a low turn count motor will give flexibility, at the cost of efficiency. You will still have plenty of torque (the controller will provide the current). You will have a phenomenal top speed with the combination of high pack voltage and fast motor.
But you get lower efficiency and range, and you pay for more FETs in the controller, and possibly reliability (overheating of the motor, possibly failure of the controller due to the stress).
ZapPat
10 kW
I think there is some confusion here about the terms I used above... when I said 'phase wires', I meant the motor wires that go from the controller to the motor and through the axle, but I did not mean to include the actual magnet wire making up the motor coils. In any two equivalent motors, the controller-->motor wires used are the same no matter what magnet wire arrangement is used inside the motor, and this is the part of the motor wiring that gets less stress if you use a slow wound motor (higher phase voltage) vs a fast wound motor (higher phase current).EVan said:
However the windings themselves will not change the motor's internal efficiency no matter what series/parallel arrangement is used. In EVan's example above for example, the slow wound motor would have 4 times the resistance, not 2, so basic efficiency for these windings is the same. However, a complete system using a slower wound motor driven at full speed (WOT) will have better global efficiency than the equivalent fast wound motor system being used at part speed during steady cruising. Less controller and phase wire losses (lower phase current) along with little or no PWM happening reduces controller switching and motor losses... but you loose the possibility of a higher top speed. You also loose torque as the motor's BEMF approaches the battery voltage, so a higher speed system runing at partial output could feel 'stiffer' than a lower speed system runing at full throttle.
shinyballs
1 kW
Anyone has any experience with Tefzel insulated wire?
They can be had cheaper but not sure if the thickness is the same as Teflon, thinking about using 12awg...
http://www.aircraftspruce.com/catalog/elpages/unshieldlwire.php
http://nepp.nasa.gov/npsl/wire/22759/22759_16.htm
View attachment Military Wire.pdf
TEFZEL ETFE, rated at 150°C, Is a melt processible fluorocarbon thermoplastic combining many of the desirable properties of Teflon and Kynar. Mechanically it is tough, and has excellent flex life, and Impact, cut-through and abrasion resistance. Electrically It Is an excellent low loss dielectric and has outstanding electrical properties. Additionally, It is weather resistant, Inert to most solvents and chemicals and is hydrolytically stable. Like irradiated polyethylene It has excellent resistance to high-energy radiation. Insulation thicknesses from 5 to 100 mils are available.
They can be had cheaper but not sure if the thickness is the same as Teflon, thinking about using 12awg...
http://www.aircraftspruce.com/catalog/elpages/unshieldlwire.php
http://nepp.nasa.gov/npsl/wire/22759/22759_16.htm
View attachment Military Wire.pdf
TEFZEL ETFE, rated at 150°C, Is a melt processible fluorocarbon thermoplastic combining many of the desirable properties of Teflon and Kynar. Mechanically it is tough, and has excellent flex life, and Impact, cut-through and abrasion resistance. Electrically It Is an excellent low loss dielectric and has outstanding electrical properties. Additionally, It is weather resistant, Inert to most solvents and chemicals and is hydrolytically stable. Like irradiated polyethylene It has excellent resistance to high-energy radiation. Insulation thicknesses from 5 to 100 mils are available.
auraslip
10 MW
- Joined
- Mar 5, 2010
- Messages
- 3,535
Hey guys,
I was wondering what supplies to use to do this mod.
For the hall sensor and temp sensor wires I was wondering if 36gauge teflon coated wiring would work? http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=11850
Seems like it'd make it a lot easier to 10gauge phases down the axle. Would it be advisable to heat shrink all of them together to prevent shorts?
Would voltage drop from the 36 gauge wire cause problems? If so, what would be the minimum size to use?
For using 10 gauge wire, is the heat shrink used standard hobby king heat shrink? What size?
For using 12 gauge wire, what is a good source for teflon coated wire?
thanks
I was wondering what supplies to use to do this mod.
For the hall sensor and temp sensor wires I was wondering if 36gauge teflon coated wiring would work? http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=11850
Seems like it'd make it a lot easier to 10gauge phases down the axle. Would it be advisable to heat shrink all of them together to prevent shorts?
Would voltage drop from the 36 gauge wire cause problems? If so, what would be the minimum size to use?
For using 10 gauge wire, is the heat shrink used standard hobby king heat shrink? What size?
For using 12 gauge wire, what is a good source for teflon coated wire?
thanks
liveforphysics
100 TW
steaveford said:
Dont you guys love the crazy sheet that spammer bots randomly generate?
liveforphysics
100 TW
auraslip said:
I made this follow up thread that holds your hand through the process.
http://endless-sphere.com/forums/viewtopic.php?f=2&t=24547&p=355535&hilit=+10awg+9c+upgrade#p355535
liveforphysics
100 TW
auraslip said:
liveforphysics
100 TW
Wooot! Love it! I want a pedobear costume.
Did you notice my shirt in the picture from the top of the hillclimb?
Did you notice my shirt in the picture from the top of the hillclimb?
Hyena
10 GW
Heh yeah I noticed that.liveforphysics said:
I had my photo taken for an article in the paper last week and was so tempted to wear a pedobear shirt but figured it might not be a good idea considering I was representing my work :lol:
Continuing the OT, it's almost odd that you'd like PedoBear so much, given that it is highly likely it's origin was SafetyBear.
(although, the Safety was supposed to be about child safety, preventing molestation/etc, not safety about bikes or stuff like that).
(although, the Safety was supposed to be about child safety, preventing molestation/etc, not safety about bikes or stuff like that).
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