ECN Forum Forums General Topics of the Trade General Discussion Area Schneider LC1D09

You have run into the difference in philosophy between IEC and NEMA contactor designs. Everybody thought IEC contactors were great because they were cheaper and smaller than NEMA contactors, and according to the sales literature, lasted just as long. But the story they tell leaves out a LOT of information. They are not at all the same, and you can see that in this photo of contacts rated for the same motor current:

In addition, NEMA contactors are designed around 1 million electrical operations, but 6 million mechanical, meaning the contacts are expected to be replaced at least 6 times. IEC is designed around 1 million electrical operations under perfect conditions, then they are thrown out. There is nothing repairable in them. But really you must determine exactly how often your machine is going to start, under what conditions, and predict how long you want the contactor to last. They give you a long complicated set of charts for engineering each and every contactor specifically for each machine. But we don't bother with all that here in North America, we were used to NEMA concept; throw the worst you can at it and it survives, if it's easier than that, it survives longer than you. When an OEM mixes the NEMA mindset against the IEC cheapness, the end user suffers in the long run. All the OEM was concerned about was lasting out their warranty...