Cable
Cable
(OP)
I am looking for a cable to transport a 3kV, 500kHz signal over a few meters. When using standard cables (or high voltage rated cables), the signal tends to decrease to 1 or 2 kV after 1 or 2 meters.
Any suggestions of cables I could use?
Thanks!
Bart
Any suggestions of cables I could use?
Thanks!
Bart





RE: Cable
Look in the general direction of large diameter RF coaxial cable. Some of the larger ones are capable of handling 3kV and, as a bonus, will carry 0.5 MHz with essentially no loss.
RE: Cable
RE: Cable
RE: Cable
RE: Cable
Perhaps we need more details...
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RE: Cable
Smelly. Very very smelly.
RE: Cable
I think that essentially the issue is the frequency. When I transport a similar signal at a lower frequency, everything works fine.
Jimkirk, source output is of the order of 1nF.
Davidbeach, how did you calculate the 166A? Was this at 50/60Hz?
VE1BLL, measurements were done using an oscilloscope with a 1000/1 differential probe (input impedance 20pF).
RE: Cable
RE: Cable
RE: Cable
Find out the inductance of the cable at a given frequency.
The inductance of the cable at 500khZ will be 8333 times that at 60hz. 1 ohm inductive reactance at 60hz becomes 8333 ohms at 500khz. (Z=2*PI*f*L)
so a current of 0.00012A (0.12mA) will cause drop of 1kV (This is IF 1 ohm/ft is a correct assumption)
RE: Cable
RE: Cable
RE: Cable
Is the 500kHz still a nice clean sine wave at the far end?
Does the probe + scope indicate 3kV at the input to the cable?
Is the cable open circuit at the far end?
And most importantly of all, what the heck are you doing with 3kV of 500kHz ????
(PS: Is 500kHz still a distress frequency? It used to be.)
RE: Cable
Something more about the measurement: 3kV is measured at the output of the source, when no cable is applied. 1 kV is measured at the far end of the cable (so with the cable connected to the source). I have a feeling it is the C that is causing this trouble and not the L (no current is flowing), but of course any fresh ideas on this are welcome.
BTW, the signal is used in the igniter of a discharge lamp.
Bart
RE: Cable
($2 on 'in the source' please...)
RE: Cable
It might be a simple test to show your cable is ugly.
Also, check your cable with an ohm meter, maybe you'll be surprised.
kch
RE: Cable
Your signal has a period of 2 us. Assuming that your desired rise/fall time is 0.2 us, the dv/dt = 15 kV/us, which is quite sporty, even for a high-performance op-amp. Since you're getting as much as 2/3 rd reduction, your driver is undersized by at least a factor of 3. Conversely, you cannot run faster than about 100 kHz with this driver and this load.
With a 1 nF load, the displacement current is 15A, further increasing the sportiness.
TTFN
RE: Cable
You cannot use standard wire to transmit the 500kHz (skin effect)
RE: Cable
http://www.timesmicrowave.com/products/
Benjamin Lanz
Vice Chair of IEEE 400
Sr. Application Engineer
IMCORP- Power Cable Reliability Consultants