What is zero point crossing (noiseless) switching?

In an AC circuit ideally one should switch off the banks of capacitors as the voltage (or current) crosses zero. In this way there is not only no chance of creating any unwanted electromagnetic emissions, but also the phase converter puts least stress on the electrical network, and finally the phase converter itself is subject to least stress.

However all phase converters except for Boosters use electromechanical contactors (relays) to switch the different banks of capacitors on or off. It is impossible to set up these electromechanical devices such that they will reliably and consistently achieve a zero point crossing switching. Even those few manufacturers who try to do this can only guarantee it when it leaves the factory - and most don't even try that. The result is that the electromechanical components fail in service, which is expensive (not just the parts but also the service calls and lost production) and the neighbours get annoyed with the interference. The solution is simple: buy a Booster!!