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Mains Was: Low cost SMD Oven for making SMD samples and Prototypes
The other was a small base station which had its power input connections
designed by Mechanical engineers. ----------------------- I wouldn't blame the mechanical engineers. I'd blame the engineering manager who let mechanical engineers design an electrical interface, and then apparently didn't design-review it. Joe W3JDR "Steve N." wrote in message ... "Highland Ham" wrote in message ... I knew that I already had two phases in the guest room. A couple of cheap extension cords was all it took, with one blade of a "three prong adaprer" inserted into each hot side of each extension. Guest 220 in 5 minutes! I'd feel ok drawing 8A this way, but you shouldn't try this at home...I'm a professional. (:-) Linears should have either 1- both 110 and 220 internal wiring options, or 2- just 220 But 120 is is a real stretch. ====================== Steve , Tnx for providing the 'full' picture. Assuming a 67 percent efficiency (am I too pessimistic?) a legal RF power amp would need 1.5*1500 = 2250 W (say overall maximum of 2400W) which at 220 V means 12 Amperes. So, a shack without 220 -234 V power supply would need a dedicated supply from the switchboard . Here in the UK we do have 115V industrial power tools,which need to be used with a 230/115V (usually portable) safety transformer with the secondary having an earthed centre tap ,such that in the event of a 'fault' personnel is exposed to a (peak) voltage not exceeding 1.4*58 = 81V which is considered sufficiently low to prevent electrocution. The nominal domestic supply voltage within EU countries has now been 'normalised' to 230V ,meaning that (within a voltage band) the same equipment can be used in all the countries. Before , the UK had 240V and continental countries 220V . This often meant that for example an (clothing) iron for 220 V had a very limited life when used in Britain . The voltage at my place (rural area) is nowadays usually 236-237 V ,whereas earlier it was up to 250 V or sometimes even higher. Frank GM0CSZ / KN6WH In the cell phone base business, everything (almost) runs off battery systems. There were two cases where Development Engineers not knowing about our mains system, where developing products never before run off the mains. In one, the presence of "both" 120 and 240 was causing some spike absorbers, designed for 120 systems, to pop from the 240. The other was a small base station which had its power input connections designed by Mechanical engineers. It came to my test group without the power cord connected to the black (protorype) "barrier terminal strip". One of the Develpoment Engineers called another for the connections and made them. It was plugged in, but wouldn't work. Several Engineers started checking and discuvered that the serial port on the control laptop had been fried. Several of us put our noses to the connector and could smell the burned components on the unit. We also noticed that the heat sink wasn't getting warm. I and several Engineers put our hands on the case to test this. Note: In the US, we have a third wire in all outlets which, though it is the same as the common or neutral (basically also ground or no potential) side, it is used to connect to any exposed metal parts. The purpose it to divert any hahazzardous shorts to ground and blow a breaker or fuse rather than harming someone. We were focused on finding the cause. Several of us worked trying to analyxe the failure and found the serial interface of the unit has fried as well as the lap top serial port. Findings: The HOT of the 120 ( instead of the safety ground connection) was connected to the chassis. This placed the outside of the (as yet unpainted) housing at 120 VAC relative to all other grounded equipment in the room! I was one of several who put his nose up to that hole to smell burnt comopnents. I was one who felt the unit for heat build up. It hit me half way home. Needledd to say, I gave the Mechanical and Electrical Engineers a lecture on mains principles. 73, Steve, K9DCI |
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