Siemens Masterdrive

Have you tried calling Siemens?

Try running with nothing connected on the output terminals, if it trips the same its definitely an internal fault.

Whether the internal fault (probably output transistor failure) is a faulty component or caused by installation / operation should be addressed by the original supplier - is it under guarantee or service contract. If you do go for repair, try to go somewhere where they've got good experience and diagnostic skills that may help prevent further problems.

If you end up paying for a replacement rather than repairing (repairing can end up with a 'faint friend') depends on the cost of it not being in action to you, but if you're paying for a complete unit you should consider changing manufacturer also to a more robust / reliable unit for your job / environment. Are you sure its not contaminated, for example?

Thanks for your comments.