# 100HZ signal producing

1. Oct 20, 2007

### m.s.j

One electromotor serviceman who worked in a small workshop needed an ac power supply with 100HZ frequency.
He knew that in synchronous generator, if the magnetic flux of the field system is distributed perfectly sinusoidal around the air gap, then e.m.f generated in each full-pitched armature coil will be sinusoidal completely.
He had an old and small 50HZ generator. He decided to use it for 100HZ signal producing.
For this purpose, he changed standard distributed windings of armature that located in stator slots. Also he connected one electronically mid-pass filter which tuned with 100HZ frequency in generator output.
The output voltage of generator was not sinusoidal and it is distorted by new space flux distortion. He had a lot of harmonics in output stage of generator, but he never observed 100HZ signal in filter output.
He more and more tried and changed the stator winding distribution frequently, but he couldn't to produce purposed signal.

Why? Why couldn't he?

BEST REGARDS
MSJ

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Creative thinking is enjoyable,Then think about your surrounding things and other thought products. http://electrical-riddles.com

2. Oct 20, 2007

### NoTime

Since this question is on the riddles link, I'll guess it isn't homework.

While multipole design is not a strong point a couple things come to mind.
1) You need to double the winding count. It seems improbable that there would be enough slots.
2) You can't change just the stator as the question states.

3) The simple solution would have been to double the shaft speed.

3. Oct 27, 2007

### m.s.j

According to electromagnetic laws, the curl of electrical field (E) must be zero, for the circulation is zero, and the curl of magnetic field (H) is not zero, however; its circulation per unit area is the current density by Ampere's circuital law.Therefor in all magnetic systems, if some magnetic flux lines export from a surface of one volume of space, then same flux lines import to that volume via its other surfaces.
It means, for mathematic function of magnetic flux we can write: f(-x) = f(x) that named odd function.
Also according to Fourier analysis, each periodical odd function can be written with the sum of odd harmonic elements. So the serviceman can never produce even harmonic flux ( 100HZ,200HZ,…) in generator gap.

BEST REGARDS
MSJ

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Creative thinking is enjoyable,Then think about your surrounding things and other thought products. http://electrical-riddles.com

4. Oct 29, 2007