Author Topic: Flywheel magnets losing strength, any experience out there?  (Read 810 times)

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Offline sleepy

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #15 on: October 15, 2017, 11:40:59 PM »
A rotating electrical machine can not produce DC directly. All rotating machines produce AC and it is converted to DC via either a solid state rectifier or a mechanical commutator. The very nature of a rotating permanent magnetic machine makes direct production of DC impossible as the coils or windings passing both north and south poles of the magnet which is unavoidable. The frequency of the AC is dictated by number of poles and speed. The modern stators must contain the rectifier internally.

When you hold a modern DC stator in your hand the rec/reg must be microscopic. On KTMs  around 2010 the stators change from 8 pole to 12 pole like this but the wiring certainly has no rec/reg. Trailtech seem to think they have DC stators ?
http://www.trailtech.net/stators-flywheels/ktm-stator-kits/s-8362-05

Why do they have one of these if they are DC output.
http://www.4mxracing.net/product/regulatorrectifier-ktm-sx-f-450-factory-edition-2015-2016/
The 2 yellow wires are a dead giveaway that it is AC coming out. If it was DC you would only need 1 wire for the positive and neg would be earth/engine case. With the 2 yellow wires which one is the positive if it is DC?

HeavenVMX

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #16 on: October 16, 2017, 12:55:05 AM »
yes this is mainly true with some exceptions.

 if the stator is a permanent magnet (or excited by a dc field winding) and the rotor has a commutator
then you do get dc generated directly (like a Tachometer, DC Generator) in the case of a tachometer the voltage is directly proportional to the speed in RPM.

As I said Hoony there must be a rectifier or commutator (which is a mechanical rectifier) to convert the raw AC to DC.

The example of a tacho is an interesting one as they are a specialised device that is specifically designed to give very accurate voltage directly proportional to speed (within the design speed range). The output is a voltage with very little current capability (mA) as once current increases even slightly the voltage / speed ratio strays. These devices have many poles and a large iron circuits for their specific output. As we agree they usually have commutators therefore the generated signal must be AC otherwise it would not need one. The output is also not necessary a linear voltage/speed relationship it can be a squared, square root or exponential curve depending on design and application.

Modern tacho instruments use proximity devices or similar to count targets instead of traditional tacho generators
« Last Edit: October 16, 2017, 01:30:23 AM by HeavenVMX »

HeavenVMX

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #17 on: October 16, 2017, 01:00:00 AM »
A rotating electrical machine can not produce DC directly. All rotating machines produce AC and it is converted to DC via either a solid state rectifier or a mechanical commutator. The very nature of a rotating permanent magnetic machine makes direct production of DC impossible as the coils or windings passing both north and south poles of the magnet which is unavoidable. The frequency of the AC is dictated by number of poles and speed. The modern stators must contain the rectifier internally.

When you hold a modern DC stator in your hand the rec/reg must be microscopic. On KTMs  around 2010 the stators change from 8 pole to 12 pole like this but the wiring certainly has no rec/reg. Trailtech seem to think they have DC stators ?
http://www.trailtech.net/stators-flywheels/ktm-stator-kits/s-8362-05

Thank you Looza have a look at the page you linked

The bottom left spec section states

70 Watt High Output DC Stator for 13-15 KTM 450 SX-F & XCF
Use OEM regulator/rectifier and flywheel.

It seems to make it clear that the bikes has a Rectifier/Regulator that must be used therefore the stator even though they call it a DC stator actually produces AC. Look at the stator and then imagine the magnets in the flywheel passing each pole. Every pole will experience a North pole and south pole of every magnet in the flywheel = AC output.

I think you will find they call them DC stators to avoid confusion when in actual fact it is confusing for anyone that does not understand electrical theory.

One reason for the compactness is that they progressively increase the number of poles as you say 8 poles increased to 12 poles this increases AC frequency by 50% at the same RPM. This in itself will increase output once the higher frequency passes through a full wave rectifier.

Every wiring diagram I look at on the WEB for KTM 450 SX-F EXC KTMs shows a rectifier/regulator
« Last Edit: October 16, 2017, 01:48:20 AM by HeavenVMX »

Offline fred99999au

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #18 on: October 16, 2017, 04:52:25 PM »
Nah, they only use magnets with north poles on them. Voila DC.

HeavenVMX

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #19 on: October 16, 2017, 05:15:19 PM »
Nah, they only use magnets with north poles on them. Voila DC.
That explains it  ;) ;) ;) ;D ;D

Offline Hoony

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #20 on: October 16, 2017, 07:10:53 PM »
Nah, they only use magnets with north poles on them. Voila DC.
That explains it  ;) ;) ;) ;D ;D

made by elves ;)
Long time Honda Fan, but all bike nut in general, Big Bore 2 stroke fan.    http://www.youtube.com/watch?v=XJoKP6MawYI
1985 Honda CR500RF "Big Red"
1986 Honda CR250RG
2005 KTM 300EXC "The GruntMeister" ( I love that engine)

HeavenVMX

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #21 on: October 16, 2017, 07:49:33 PM »
North Pole Elves obviously :-X

Offline Lozza

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Re: Flywheel magnets losing strength, any experience out there?
« Reply #22 on: October 18, 2017, 05:31:34 PM »
A rotating electrical machine can not produce DC directly. All rotating machines produce AC and it is converted to DC via either a solid state rectifier or a mechanical commutator. The very nature of a rotating permanent magnetic machine makes direct production of DC impossible as the coils or windings passing both north and south poles of the magnet which is unavoidable. The frequency of the AC is dictated by number of poles and speed. The modern stators must contain the rectifier internally.

When you hold a modern DC stator in your hand the rec/reg must be microscopic. On KTMs  around 2010 the stators change from 8 pole to 12 pole like this but the wiring certainly has no rec/reg. Trailtech seem to think they have DC stators ?
http://www.trailtech.net/stators-flywheels/ktm-stator-kits/s-8362-05

Thank you Looza have a look at the page you linked

The bottom left spec section states

70 Watt High Output DC Stator for 13-15 KTM 450 SX-F & XCF
Use OEM regulator/rectifier and flywheel.

It seems to make it clear that the bikes has a Rectifier/Regulator that must be used therefore the stator even though they call it a DC stator actually produces AC. Look at the stator and then imagine the magnets in the flywheel passing each pole. Every pole will experience a North pole and south pole of every magnet in the flywheel = AC output.

I think you will find they call them DC stators to avoid confusion when in actual fact it is confusing for anyone that does not understand electrical theory.

One reason for the compactness is that they progressively increase the number of poles as you say 8 poles increased to 12 poles this increases AC frequency by 50% at the same RPM. This in itself will increase output once the higher frequency passes through a full wave rectifier.

Every wiring diagram I look at on the WEB for KTM 450 SX-F EXC KTMs shows a rectifier/regulator

I went all over a friends CRF450 and couldn't find the rec/reg but partzilla shows one there...........pointing north  ;)
Jesus only loves two strokes