I don't know if you tried to contact KeyTek or not, but we have both applications people and engineers who understand the ECAT system in detail. It is still our primier Surge tester and has evolved significantly with new capabilities and enhancements on a regular basis.
To take your issues one at a time: "However, I do not fully understand the discharge network and do not know, for instance, if the total joules delivered to the coupler is independent of load or impedance. Energy delivered works like power: The maximum energy you can deliver to a load is when you have matched conditions: If the load impedance is equal to the surge generator source impedance, the most energy that can be delivered is one-half of the energy stored in the network. If the load impedance is different, the delivered energy will be less. Therefore, energy delivered IS dependant on the load impedance, but all the impedances involved on the ac mains are complex and are different for every AC line, coupler and EUT. (You can do some simple calculations using resistors in place of the EUT's and assume the generator source is purely resistive and you'll see how the energy fluctuates as the load impedances change.) Does the network always fully discharge? -- The answer is yes, but the hard part is determining where the charge goes -- some energy is used up in the process of forming the waveform (shut resistors internal to the network), some is dissipated in the coupling network (very little), and some goes to the EUT(s). If the EUT impedance is very high -- no energy is dissipated in the EUT; if it is very low, most of the available energy will be dissipated in the EUT. When a discharge occurs, the energy storage capacitor is connected to the surge network which has a resistor connected to ground internally, so if the EUT doesn't take any energy, eventually (milliseconds) all the energy in the capacitor is discharged via the shut network resistance. Just to make sure no surge energy is left (for safety reasons) a relay shorts the network directly to ground a short time after the surge. The test you performed with the Fluke probe and scopes -- first, you need to use good high voltage differential probes to get any meaningful waves when dealing with live power lines and surges. Secondly, you don't say what the EUT impedance looks like -- for example: if both EUT's look like a high impedance compared to the source impedance of the generator (2 ohms), it is likely the voltage waveforms observed won't change when adding additiol EUT's in parallel -- until, of course, you get enough in parallel that the total impedance gets to be much lower. If the impedance of the two EUT's was very low, possible due to the use of varistors or other surge protective devices, the same thing might apply -- it won't matter whether one or both protectors operate, assuming both work, the voltage waves will be the same -- it may be; however, that all the surge current is going through only one of the protectors and the other is getting no current! I'm not familiar with the Fischer probe you mentioned, but Pearson current probes work very well. If you need a model number, let me know..... The problem your'e going to have in justifying operating both systems in parallel is that you may not be able to identify a failure -- if both are high impedance and one breaks down, it will prevent the other from seeing any surge voltage and you may not know which one broke down if you're only monitoring surge voltage. If the EUTs are low impedance (with protectors or for some other reason), it is unlikely they will share currents equally, but you won't know until you can make some surge current measurements to make sure. When the behavior of an EUT when hit with a surge is unknown, it is impossible to state that testing two EUT'S in parallel is justified. Only after understanding how each EUT will behave with the surge, will it be possible to determine how they will behave in parallel.. Good luck... If you have any other questions, please give me a call or email -- Mike Hopkins mhopk...@keytek.com or 1-800-753-9835. Mike Hopkins > -----Original Message----- > From: Dale Albright [SMTP:dale.albri...@flextronics.com] > Sent: Thursday, May 04, 2000 5:04 PM > To: wo...@sensormatic.com; emc-p...@ieee.org > Subject: RE: Surge > > > Richard, > > This was our intuitive thought too. However, I do not fully understand > the > discharge network and do not know, for instance, if the total joules > delivered to the coupler is independent of load or impedance. Does the > network always fully discharge? > > Today we spent some time to capture it. The following test was run on the > AC: One EUT was connected to the coupling/decoupling network. A digital > scope and fast Fluke probe was used to capture the voltage waveform at the > input of the EUT. The data was plotted. A second EUT was added in > parallel > to the coupling/decoupling network. The test was re-run (no moving the > probe) and the data was plotted. To my surprise, there was no change in > waveform. My expectation was to see no change in rise time but to see a > much faster decay time. > > A second test was attempted with a Fischer F-33-1 current probe. Not > successful. > > The subject EUTs pull approx. 1/4 Amp, no surge protection devices. The > test equipment is Keytek ECAT system (E4551 and E501A). > > We are proceeding to make a justification of the method (for these > particular EUTs ONLY) that the individual EUTs are not under-stressed. I > would like to seek additional input from the group. Unfortunately, most > senior staff at Keytek involved in the development of the system have > left. > If anyone knows of whereabouts, please email. Also if anyone has a > contact > at Schaffner or Haefely. > > Best Regards, > Dale Albright > > -----Original Message----- > From: wo...@sensormatic.com [mailto:wo...@sensormatic.com] > Sent: Wednesday, May 03, 2000 12:11 PM > To: emc-p...@ieee.org > Subject: RE: Surge > > > > I assume that you mean applying the surge energy to multiple power ports > (or > I/O ports). Consider the energy produced by the surge generator and how > that > energy is dissipated in the EUTs. If there is one and only one port being > tested, would not the energy being delivered to that port be much higher > than if multiple ports were being tested at the same time? I think the > answer to your question is that you cannot test multiple ports since each > of > those ports would be under-stressed. > > Richard Woods > > ---------- > From: Dale Albright [SMTP:dale.albri...@flextronics.com] > Sent: Wednesday, May 03, 2000 11:14 AM > To: emc-p...@ieee.org > Subject: Surge > > > Group, > > A question came up today regarding testing multiple EUTs for surge > (61000-4-5). I spoke with the secretary of the subcommittee 77B > (Jacques > Delaballe) on this subject. We agree that: The method is not part > of the > standard; If the results are positive (EUT passes) then maybe OK; If > EUT > fails, then indeterminate. What are your thoughts? > > Regards, > Dale Albright > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
