Speak to Andy Williams at Siemens in Manchester.
He has worked with us on plenty of projects and is probably the most helpful man you will encounter.
And the Micromaster range doesn't usually come with a filter as standard, its user specified on purchase. So you may not have one at all.
We had a similar problem with one of our plants in the early days, it turned out that because we had lots of inverters with no filtering, harmonics were going through the roof and knocking everything off.
Hope that helps somewhat.
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