how to measure the pratical magnetic flux of a claw pole of car alternators?
I want to know whether the magnetic flux could be measured by test using the claw pole or not. Does anyone know this, please, please tell me.
Gaussmeter, Teslameter, Measurement of magnetic field strength
Measuring Mag Fields
The Hall Effect Sensor
http://www.datasheetarchive.com/inde...ASL0090970.pdf
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Thank you for your answer, but what you said is how to use some device to measure magnetic flux, whether it can be measure by test and by myself or not.
You can see the picture, now I want to measure magnetic flux of a claw who is the rotor of the alternators.
Is there any method to achieve?
claw pole
If you analyze the magnetic rotor field exactly, you'll notice, that the flux will be different at different places of the pole cross section. So which flux do you want to measure?
Technically, you can either measure induction B with micro hall sensor at different places of the air gap and integrate over the cross section. Or place an induction loop around the cross section of interest and switch (preferably reverse) the excitation.
Thank you for your answer, I want to measure magnetic flux of some cross sections and one claw you can see the picture,
you said using induction loop around the cross section, it can measure magnetic flux of some cross sections, but how to measure
magnetic flux of the whole claw?
http://i1140.photobucket.com/albums/...0911230232.png
You can place the induction loop around the excitation winding.
Whether it must meet some requirements for the induction loop around the excitation winding or not, because the shape of claw is quite complex,
and when I use the induction loop around the excitation winding, How can I measure the induction B, becaus it is heterogeneous for the whole
claw?
By the way, can it use the Inexpensive magnetic flux (gauss) meter to measure in 'http://www.rcgroups.com/forums/showthread.php?t=307133' ?
Thank you for your attention.
I referred to B measurement, because hall sensor have been suggested in the discussion. But you hardly get an integral flux measurement using hall sensors. I'm not sure however, what you want to achieve.
It would be helpful to sketch the magnetic circuit and decide, which flux you want to know.
I guess, a designer, who want to know the excact field configuration of the alternator, would refer to a FEM simulation, e.g. using ANSYS, instead of measuring individual flux contributions.
P.S.:
I don't know, it they are thin enough to fit the alternator air gap. An you only get point by point B measurements.
Thank you for your detailed answer. For all I know, some company measure the singe magnetic of claw rather than in the alternator,
because the magnetic field of claw can be exactly loaded through permanent magnet or Electricity coil, do you think whether it is feasible
or not, how about the measurement precision?
You mean, they are measuring the claw field without the stator? But the field will be completely different then, what's the purpose of the measurement?
Because the magnetic field is generated by two claws, and the stator can not change integral flux of claw, we want to get integral flux of claw to
evaluate whether the claw is good or bad to generate electricity. Do you think it is feasible?
Of course it does. The excitation winding generates a magnetical field H according to N*I, the induction B and total flux is defined by the magnetic circuit, particularly the air gap. Please refer to elementary magnetostatic equations. Magnetic circuit - Wikipedia, the free encyclopedia
Thank you, I think I make a mistake, I neglected the magnetical field of the excitation winding, two magnetical field will happen mutual effect.
So the stator can not be neglectful. We want to get the magnetic flux of claw tip and root, but it is diffcult to measure the magnetic flux in the
alternator, because the claws is rotating when you want to measure in the alternator, and the air gap is so close between the claws and stator,
is there any good approach to measure the magnetic of claw tip and root?
If you only want to compare devices against known good exemplars, you can measure B at a defined position at the claw surface. Measuringair gap B of the assembled alternator should be still possible with a thin hall sensor, you don't need to rotate the claw for th emeasurement.
I wonder however about the purpose of the measurement. A defective excitation winding is the only fault I can imagine. It should also reveal in a resistance measurement.
We want to know the relationship between the magnetic flux of claws and the alternator performance, and the alternator can be disassembled or not.
Can gap B between the claws and the stator represent the claws performance? Is the difference very large if we do not rotate the claws?
Yes, if it's varying between exemplars.
There should be no big difference for the unloaded alternator. With load current, the flux may be reduced.
Thank you. You said using the micro Hall sensor to measure gap B, so the whole Hall sensor must be in the air gap, but the air gap
is usually very narrow about 0.25-0.4 millimeter, can gap B be measured by the Hall sensor or other sensor?
That's small. 0.6 mm hall sensors are still industry standard, e.g. Toshiba THS129.
Induction loop would still work. But you need either to switch the excitation current, or move the coild in and out of the air gap, and integrate the voltage peak.
Thank you very much. This method is feasible for the unloaded alternator, but we also want to measure the load alterntor, must we cut the alternator?