Hub motor temps on 28 cell 3500li

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antiscab
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Re: Hub motor temps on 5000li
BTW I was wondering is there a chance my 3500 is running cooler (the motor) because of the higher voltage.

Yup - it probably is running cooler because with higher voltages you'll draw lower amps resulting in less heat.

This is only true of the battery side.
The motor side will see the same number of amps (average) regardless of an increase in battery voltage. (torque is proportional to average motor-side current)
the only downside to a higher voltage on the controller input is increase ripple current on the motor side.
This increase the RMS current which *increases* motor heating (measurable, but not significantly).

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

jdh2550_1
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Re: Hub motor temps on 28 cell 3500li

the dragging effect is caused by a short between two (or maybe 3) of the phases.
aside from rewinding, theres not alot that can be done.

Matt

EDIT: since this is the second motor to have failed after (short) use, its likely the failure is due to insufficient insulation between the windings. This results in rapid breakdown and a short between the phases.

We have a 6kW motor from Kelly which we killed in a similar fashion - however the shorting for us didn't occur in the windings but in melted insulation on the power wires (i.e. the power wires heated up and the insulation melted causing a short between the phases at this point). We mounted a second 6kW motor yesterday and we didn't melt the wires this time - but we did melt the cable wrap we'd put around them...

Jeb - Two thoughts:

1) Check the power wires to the motor and also check the hall sensor wires. Even though the power wires might have survived the hall sensor wires are routed right next to them. I don't think shorted hall sensors give the drag - I think it has to be a short between the windings.

2) If you do find a short consider upgrading the size of the power wires and the quality of the wires insulation (get something rated for high temp).

---

BTW - we're not planning on using the 6kW on our bike.

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

jdh2550_1
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Re: Hub motor temps on 5000li
BTW I was wondering is there a chance my 3500 is running cooler (the motor) because of the higher voltage.

Yup - it probably is running cooler because with higher voltages you'll draw lower amps resulting in less heat.

This is only true of the battery side.
The motor side will see the same number of amps (average) regardless of an increase in battery voltage. (torque is proportional to average motor-side current)
the only downside to a higher voltage on the controller input is increase ripple current on the motor side.
This increase the RMS current which *increases* motor heating (measurable, but not significantly).

Matt

Matt -

Thanks much for the explanation and for correcting me.

For those that might be worrying about blindspots in my knowledge and how it relates to our bike - don't worry. I'm the PHB (pointy-haired boss - a reference to the Dilbert cartoons) - we have a Chief Engineer who knows this stuff. Apparently I know just enough to be dangerous - but hey - at least I'm still teachable!

Thanks again Matt - your explanations on a variety of posts now have always been very straightforward and easy to follow. Kudos!

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

garygid
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Re: Hub motor temps on 28 cell 3500li

jebbers,
In your first picture, do some of the magnets look flat, and others look a bit concave side-to-side?
Is that strange, or normal?

In the second picture do some of the between-pole "stuffing" pieces look like they stick out a little?
Is that also normal?

Shorts from one phase winding to another should be relatively easy to detect with external resistance-between-windings measuremants. Shorted turns in one winding might show up as resistance changes, or possibly inductance changes, depending on where the short is.

If the motor is dragging mechanically, rotating the motor (wheel) very slowly (bike on center stand) with just light finger pressure might detect the drag. I think (not sure) that a shorted winding should not have very much effect when rotating the motor quite slowly. If detectable, it would probably feel like a slight "bump, bump, bump" as the shorted pole passes over the magnets.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

jebbers
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Re: Hub motor temps on 28 cell 3500li

So the dragging effect is caused by the magnets pulling the shorted windings as one chuck of metal? The wheel feels like its seizing with the outer part of the wheel.
I have a question on the stock motor. Whats with the duel set of sensors? Just pick a set?

garygid
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Re: Hub motor temps on 28 cell 3500li

It sounds like this 6kW motor should be avoided?

Where does this 6kW motor come from?
Is there a manufacturer and model number?

It also seems like some of these motors are "named" after their short-term peak power handling capability, and lack specifications for their "true", perhaps more useful, (maximum continuous) power rating.

What good is a "5500" watt motor name if the motor can only handle 2000 watts continuous without overheating (and either shutting off due to a thermal switch, or self-destructing)?

A motor "10-second burst" peak on a cool day does not really help one design a practical, usable, reliable propulsion system.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

antiscab
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Re: Hub motor temps on 28 cell 3500li

Thanks again Matt - your explanations on a variety of posts now have always been very straightforward and easy to follow. Kudos!

happy to help.
ive found on my own learn experience that a single enlightening post can save hours of googling. the EVDL and EVtech archives are a goldmine in this respect (look for anything Lee Hart, Otmar, or any of the other EV old-timers posts)

Shorts from one phase winding to another should be relatively easy to detect with external resistance-between-windings measuremants. Shorted turns in one winding might show up as resistance changes, or possibly inductance changes, depending on where the short is.

for wye-connected motors, your ohm-meter will have to very accurate indeed to measure this, as all 3 phases are connected at the centre (the variation would be around 0.0001 ohms)
another more conclusive (though perhaps not as easy?) way would be to spin the motor and measure the voltage between the phases (with an analogue volt meter preferably, and 3 of them at the same time)
if one is shorted, it will show up for a voltage test.

i did come across this a few weeks ago that makes motor and controller testing a little easier:
http://www.ebike.biz/testmeter3.htm

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

Mikie
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Re: Hub motor temps on 28 cell 3500li

Hey Guys--I really appreciate your helping out Jeb with the 6kw motor. I think he neglected to mention that there was bamboo holding some wires apart. I am watching the riding season go by here in Seattle but that just may lead to some better understanding of this whole process. Matt that is a great link to the page for the tester AND as I scrolled down I found there was another page with even more hidden gems including a 10kw brushless hub motor mercy me....

http://www.ebike.biz/other%20items.htm

Thanks again for all your help....Mikie

mikie

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