James, I am planning on-site testing of 120 kW industrial switch-mode power conversion equipment using EN50081-2 and EN50082-2 for generic standards. I want to tool up for 400 Amp testing.
In the emissions standard you will find allowance and direction for "in-situ" testing. Even though this is meant for testing at the "end point of use", I believe it to be applicable to the manufacturer site also as long as you can show that the setup is significantly similar. My test lab concurs. In the past I have used a Schwarzbeck TK 9416 test probe and a Taskoph test probe without LISN's for conducted measurements, as allowed in the standard. But now I am finding some problems when the test is compared to a recent test using LISN's. The equipment failed miserably. Either there was a problem in calculating the proper offsets the probe introduced (20 dB) on the original test or else my application is extremely sensitive to line stabilization. I modeled the probe circuit on spice and found that a frequency sweep does not exactly match the claims of the probe manufacturer. I have not been able to obtain a probe of my own to put on my impedance analyzer so the jury is still out. I think the best choice is to use LISN's wherever it is possible. LISN's can be difficult and expensive so I plan to build my own using 2/0 or 4/0 EPDM wire for coils and have a certified local EMC test lab check calibrations. I don't believe that connecting to 400 Amp LISN's should be too difficult using Superior Electric pin and sleeve connections for input/output power, otherwise I will be looking at Multi-Contact Corp., as they have connection systems ranging up into the kAmps. For enclosures I will be using deep-drawn metallic enclosures with finger stock on the seams. Measurement probes will be built into the LISN as well. Power rated attenuation pads and terminators are essential in your tool kit. CISPR 16 describes the circuit and testing required for the LISN's. Because of our factory background noise I will also need line filters prior to the LISN's. Once again commercial versions are very expensive and I will probably build these. The addition of an isolation transformer of 200 to 250 kVA (in my application) that steps 480V down to the 400V European line requirement should help reduce the background noise significantly in conducted tests. My understanding is that as long as you provide calibrated LISN's on your line, any amount of filtering you provide up front is acceptable. CISPR 16 also seems to imply that adding more L/C sections in your LISN's is acceptable. For radiated testing I will be operating the equipment here at the factory with the receivers some distance away, in a van, in the parking lot. Naturally time of day is critical but my test lab says they can deal with the problems. Also they will be here to prescreen my background with an analyzer and a logger to record the levels every 15 minutes or so. We intend to screen 1st and 2nd shift. If results are unsatisfactory then we will include a 3rd shift screen. I am currently using TV-PS in Boulder Colorado for this service and they have a van outfitted with all the equipment. They can also take the test data and write a test report for 47 CFR part 18. As for immunity testing I am going to be using a dedicated 480V line with the isolation transformer. You probably will not be able to use the 20mH in-line choke normally used with the immunity standards, especially if your equipment is for power conversion . However, the standards allow the removal of the choke as its primary purpose in life is to protect your facilities from the various line disturbances that will be induced. The isolation transformer will provide much of that protection. It also provides a convenient way to measure leakage current. Be aware that at your line levels and if you are doing any significant power conversion with closed-loop regulation, the negative impedance problem and input filter oscillations can become rather severe. I was testing a power conversion unit with only a 37 kVA input using of a Caterpillar (TM) generator for a power source. The generator output was inductive enough that the input circuits to the equipment were toast. The solution was to place delta connected 60 uF motor run capacitors on the 3 phase output of the generator. I hope these remarks serve as a fairly decent guideline to get started. As always comments are mine... Doug Powell, Compliance Engineer Advanced Energy Industries, Inc. [email protected] ---------- From: James Sketoe To: [email protected] Subject: We have, under development, a large piece List-Post: [email protected] Date: Monday, July 21, 1997 9:48AM We have, under development, a large piece of equipment which we plan to sell in Europe. Its size is 2.5 meters wide, 2.1 meters high, and up to 13 meters long. Its weight is hundreds, if not thousands, of kilograms. Power requirements are 3-phase 440 vac with line currents exceeding 400 amps. Obviously, the unit is a class A heavy industrial product. My request is for advice about qualifying the unit. Methods we are considering include emissions testing on-site in the manufacturing plant. Conducted emissions will be measured using a high voltage probe such as the EMCO 3701. Radiated emissions tests would be done when the ambient is low, for example Sunday between 0100 and 0300. Immunity tests are more difficult. Do you have any suggestions?
