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testing chokes [message #8650] Wed, 05 January 2005 17:03 Go to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Hey-Hey!!!,
I am prepering to test a choke for DC tolerance and self resonance.

For pure AC inductance, I am going to use 60cps because it is easy. A resistor in series, to determine AC current( from teh department of redundancy department ). {V-inductor/V-resistor} times {R/2Pi60}=inductance in Hy.

An adjustable current regulator with DC voltage supply greater than V-ac peak-to-peak ought to allow me to determine its DC tolerance. Say a 40 vac signal and a 200VDC supply feeding the current regualtor. Might have heat issues with the CCS, but that's OK, I can deal with that.

Any suggestions at improving this method?
regards,
Douglas

Re: testing chokes [message #8651 is a reply to message #8650] Wed, 05 January 2005 22:34 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18793
Registered: January 2001
Illuminati (33rd Degree)
Sounds like you're on track. I'd use Ohms law to determine impedance and then the inductive reactance formula (XL=2πFL, L=XL/2πF) to find inductance. I'd probably also pick a few frequencies in the expected range of the coil and average the results. DC resistance will be easy.

Re: testing chokes [message #8652 is a reply to message #8651] Thu, 06 January 2005 07:15 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Say guys; Can you all explain the term Self Resonance please.

Self resonance [message #8653 is a reply to message #8652] Fri, 07 January 2005 01:20 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18793
Registered: January 2001
Illuminati (33rd Degree)
All components have inductive and capacitive reactance, so in effect, all components are resonators. Even a resistor has inductive and capacitive values. For that matter, so do conductors. At RF frequencies, the reactive properties of circuit board traces can be a problem, and sometimes path routing is critical.

The connection leads from every component are separated by a distance, so there are two conductors separated by space. That forms a very small capacitor. When a voltage differential is applied across the device, an electrostatic field sets up in the dielectric of the air.

The wire leads into the device also act as inductors. When current flows through the device, a magnetic field is setup around the conductors. That gives the device inductive reactance.

So no matter what the device is, it has values of capacitance, inductance and resistance. There is a frequency where the device acts as a resonator, without any other components attached. This is the self-resonant frequency of the device. It's usually a very high frequency.

Re: Self resonance/Excellent,thanks [message #8654 is a reply to message #8653] Fri, 07 January 2005 06:35 Go to previous message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
nt

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