I think you will find you are confusing type A MCB's with type A RCBO's. or RCD's type AC RCD's will certainly trip too early for most uses in a workshop, but then if using MCB's with induction motors usually type D MCB's would be better, but I am a great advocate of RCBO'sFor most domestic applications in the Uk we use type B which trip at 3 to 5 times rated, ie 20A device will trip between 60 and 100 amps. Type A are very sensitive and trip at just 3 to 5 times rated and used only when certain electronic equipment is being fed and are not widely available.