I really agree with you, and I feel that the equipment today that some consider entry level is as good as the best stuff we had just 10 years ago. Thanks for your feedback!!
Great tutorial. I've never done any "high" current projects and never have done any significant inrush current studies. Never too late to learn! The Hantek cc-65 is around $50 which seems to be a great addition to the toolkit. Thanks so much.
Very informative video. 👍 When voltages are comparatively high, for example in the case of tube amp B+ voltages, I always install extra series resistors of proper value either between PT and rectifier or between rectifier and first smoothing capacitor to keep inrush current peaks in safe levels to relief the stress of rectifier and caps. Of course the price of it is small voltage and power loss but the reliability of the power supply and lifetime of caps will hopefully be much better. Even tube rectifiers, which have quite large inner resistance, love extra series resistor or choke to reduce current peaks.
Hi Eddie! Thanks for your video on current clamps and their practical use on measuring inrush current! NTCs do a great job in reducing the inrush current. I own an Oltronix B32-10R power supply. Inside sits a heavy C-core transformer that used to trip my circuit breaker like every 3rd time I was switching it on (it's a B16 thermal-magnetic, so the most sensitive one will trip immediately with a peak current of 48A and the least sensitive with 80A, also my net impedance is quite low, so my regular power outlet ist able to deliver >300A in a short circuit condition). I did decide to make and install a little PCB with an NTC in series to it's mains transformer. After this mod all my worries are gone :)
@@KissAnalog Indeed it is! Imagine your big HP power supply combined with a linear supply. Oltronix specialised on secondary switching power supplies with linear regulation afterwards. The supply by itself is perhaps from the 70's but it's still great today (sure I had to replace some caps). As I'm doing tube stuff as my hobby, I like to use it as a DC heater supply, or just for blowing up things :P Some pictures for the interested people: The Oltronix front (above my small tube psu): i.postimg.cc/VsXVLr53/vdh-oltrnx.png An overview of the power electronics (the ruler is in inches): i.postimg.cc/jSxQTCJQ/P1000464.jpg My NTC mod (the quite large copper planes are for sinking away the heat): i.postimg.cc/5NFSgZWL/P1000463.jpg
Great demo - well explained on the whiteboard and good to understand the implications of using bench power supplies for this sort of testing. Interesting to see the impact of the Thermistor. I did wonder if you were going to stick the knife switch into the circuit to give it a good connection with little to no switch bounce. Looks like the cheaper current clamp meters are pretty good for low frequency measurements.
Great video. When you get the psu hooked up to the Aleph 5 it would be great to see a distortion plot at various power levels both with and without the thermistor in circuit to see if it affects performance!? Ian
Thanks Frank! I think it is a good switch with a strong spring. I was happy that it didn’t bounce badly, but I think I do see some bounce in some shots;)
Good stuff Eddie. Want a probe for my scope to look at inrush current...as opposed to a clamp meter which non (I have found) describe how they measure inrush.
Great Question! If you don't have a clamp on probe, you can put a small value resistor in line and measure the voltage across it as you turn on power. Let me know if that answers your question;)
@@KissAnalog Yes...I did that initially and it worked...just kind of a pain. Would rather do it with an inductive probe. It will be interesting to compare my homemade probe (toroid wound with a few turns) with a commercial probe.
My Inrush current: 480Vac 3phase mains rectified at contactor closure and fed to 2800 uF cap bank. Well, okay, use a beefy series connected 20 Ohm resistor that gets shunted closed after 400 msec.
Great video and well cut, especially at 19:35 where you reset your gear, invisible:-) I was wondering about a power supply for inrush. Could you not have made a slowly charging power bank with maybe 1MuF with as low impedance and ESR as possible, use an opto-relay to avoid "bouncing" switch? In that way will you have direct, unobstructed power to connect directly to your DUT after the transformer.
Thanks for your support! Yes, that's a great question and possible solution. Some people use a relay to short out the NTC (or a resistor) after a set time. I'll show different ways how to control this in a future video. ;)
Inrush current is why folks come to me complaining their piece of gear keeps on blowing the fuse they install. I always ask if they tried using a slo-blow (like is often written on a label near the fuse holder).
Great video. Love it. Do you know difference between hantek, Tecpel CA60, pri ca 60 and ESI 695? I am looking for a comparison of accuracy. If you don't know it would be interesting seeing you make a video. Thanks again for your great presentation.
Thank you! I'll have to do more videos comparing all these probes. Have you seen this video with the Tek probe? Thank you! I'll have to do more videos comparing all these
@@KissAnalog A recently purchased P6042 is on its way to me now. I assume the cord or probe's transformer is going to be bad. It was still a good deal. I know the offset voltage is matched to the probe. So not sure how easy it will be to adapt the more common P6032 probe. We'll see.
@@KissAnalog Yes. The Tek probe is pretty cool. Thanks to your videos, I have a Tek P6042 and the Hantek now. The Tek of course needs some TLC. I've repaired the broken wire in the probe head. The calibration is tedious because I have additional problems. I fixed the ripple and extremely leaking power cap. Would you consider videoing a complete calibration of your P6042?
21:38 That funky waveform seems like ringing through a transformer. Is your bench connected straight to the mains, or are you using a isolation transformer ?
Yes that was connected straight to the mains. I think it is the transformer collapsing with the current. Then resets and tries again. Thanks Bjorn for the great question!
Hi I was thinking I've not seen them in switch mode power supplies why not used a crystal control board for switching in the time domain surely this would be quieter more accurate got a opinion or am I being crazy. make much difference having the thermistor on the primary side or secondary side of the transformer
That’s a great question, but even a switching supply can have a high inrush. Although smaller caps so it doesn’t last as long. The thermistor placed on the secondary side would see larger continuous current as the voltage is lower so the current is higher. But, that’s still a great idea - just trade offs.
@@KissAnalog yes I suppose that would but the thermistor would suffer over-current only limited to certain current? I'm not talking about switch-mode power supplies having rush of current more the crystal controlling it faster smoother is that the case? is the crystal more stable quick to responding then using a transistor or IC
You said your cap bank is 80k mF for your class a 20 watt amp is that big enough? Or is it overkill? Or what's the exact amount needed for that since class a amp?
