marc@hpiacla.HP.COM (Marc Schwager) (12/29/87)
A friend and I were discussing a connector problem the other day and
we decided to ask a more informed audience. Sooo.....
Does anyone know of a connector that meets the following requirements:
1) three prongs each carrying 50 amps at 5v DC.
2) (the killer :-) must be able to connect and disconnect hot, with
no arcing.
Please E-mail responses to me. Pointers to sources welcome.
Thanks,
marc@hpiacla
..!hplabs!hpda!hpdsla!hpiacla!marc
disclaimer: Would HP ask me to do anything this strange?ornitz@kodak.UUCP (barry ornitz) (12/30/87)
In article <4110002@hpiacla.HP.COM> marc@hpiacla.HP.COM (Marc Schwager) writes: >A friend and I were discussing a connector problem the other day and >we decided to ask a more informed audience. Sooo..... >Does anyone know of a connector that meets the following requirements: >1) three prongs each carrying 50 amps at 5v DC. >2) (the killer :-) must be able to connect and disconnect hot, with > no arcing. At this current level, sparking is likely to be inevitable. You might consider an air blast arrangement like those found in large circuit breakers or a pyro- technic driven cable cutter or disconnect. These would serve to disconnect the circuit, where arcing is more of a problem. If you are worried about explosive atmospheres and arcing, you have several options. First you need to know the atmospheric composition. From this data, there are published curves showing the maximum current that can be broken at a given voltage without producing an igniting spark. At five volts, several amps are possible but certainly not fifty [this is from memory so check the numbers before trusting me]. Capacitance and inductance must also be taken into account since they are energy storage mechanisms. If all of the require- ments are met such that the available energy is too little to cause ignition, the system can be considered to be intrinsically safe. An alternative approach is to use explosion-proof construction in which the sparking device is contained within an enclosure capable of withstanding an internal explosive ignition without allowing ignition of the outside atmosphere. Companies such as Crouse-Hinds, etc. make such enclosures. All cables in and out of the enclosure must be within grouted conduits so this approach is not good for connectors that have to be dismantled. Hubbell makes some connectors that have special mating surfaces and grommets that can be used in many hazardous locations, but generally it is required that the power must be disconnected before connections are made or broken. A final approach is to purge the connector with a non-flammable gas, maintaining a positive pressure around the connector such that the connector is never exposed to a hazardous atmosphere. Liquid immersion in a material such as oil might also work in certain circumstances. The installation of instruments and electrical apparatus in hazardous locations is a very complicated subject. While many of the techniques are based on experience rather than hard science, the safety record of the chemical industry shows that they work. I am sure everyone can point to at least one spectacular disaster at a chemical plant, but look carefully at the number of deaths or serious injuries per man hour for all major manufacturing industries. Barry ----------------- | ___ ________ | | | / / | | Dr. Barry L. Ornitz UUCP:...!rochester!kodak!ornitz | | / / | | Eastman Kodak Company | |< < K O D A K| | Eastman Chemicals Division Research Laboratories | | \ \ | | P. O. Box 1972 | |__\ \________| | Kingsport, TN 37662 615/229-4904 | | -----------------