One might get an overload signal, but this is not by any means common. Following your line, how could I test this disconnection time because I think it is very complex on the output side of an inverter.? I have never seen a set of Manufacturers Instructins which told me how to verify compliance with BS7671 disconnection times, and I have used many drives for all kinds of purposes. I repeat my comment, there is not a believable fault which requires this disconnection time anyway. It is not a case of shock protection is it? So why are you worried? The output current, power, and voltage are all outside the users control. Treating a VSD as some kind of transformer is ridiculous, it is not. The electronic disconnection on fault is many times quicker than a contactor. Contactors are many times less reliable than drives. Is this design sensible? Are there any accident statistics which suggest that it is? You will notice that many machines have drives directly connected to emergency stop systems. They are much the quickest way to stop motors and are capable of doing so in a single revolution or so (which may well wreck the motor) but that is a price of "safety". This action would always signal a fault condition because an instant change in direction at full power is not expected, so would unpower the emergency stop. Not a good idea. I agree rather strongly with whjohnson, we need to have a rethink with the 19th edition, from first principles
One might get an overload signal, but this is not by any means common. Following your line, how could I test this disconnection time because I think it is very complex on the output side of an inverter.? I have never seen a set of Manufacturers Instructins which told me how to verify compliance with BS7671 disconnection times, and I have used many drives for all kinds of purposes. I repeat my comment, there is not a believable fault which requires this disconnection time anyway. It is not a case of shock protection is it? So why are you worried? The output current, power, and voltage are all outside the users control. Treating a VSD as some kind of transformer is ridiculous, it is not. The electronic disconnection on fault is many times quicker than a contactor. Contactors are many times less reliable than drives. Is this design sensible? Are there any accident statistics which suggest that it is? You will notice that many machines have drives directly connected to emergency stop systems. They are much the quickest way to stop motors and are capable of doing so in a single revolution or so (which may well wreck the motor) but that is a price of "safety". This action would always signal a fault condition because an instant change in direction at full power is not expected, so would unpower the emergency stop. Not a good idea. I agree rather strongly with whjohnson, we need to have a rethink with the 19th edition, from first principles
