111
General Mach Discussion / Re: Any help / suggestions please?
« on: October 10, 2016, 08:33:23 AM »
I didn't finish this one off.... 'll have a go here, but I've kind of lost my chain of thought...
There is a bit of waffle over here on the UK earthing arrangements..... basically although the nomenclature is UK based, if you consider the wiring arrangements it kind of covers every possible permutation of the incoming earth....
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj2o6ycm9DPAhXKJsAKHZUuDeMQFggfMAA&url=http%3A%2F%2Felectrical.theiet.org%2Fwiring-matters%2F16%2Fearthing-questions.cfm%3Ftype%3Dpdf&usg=AFQjCNGgVmZa42MaWWheFH0je93n2TQVdg&sig2=12kT_2cmztOW93h4-zaNaA&bvm=bv.135258522,d.d24
Because cnc systems work on lower voltages, we have step down transformers or switched mode power supplies.
Both of these allow for electrical isolation of the primary (mains) and secondary (lower voltage) sides and all use some form of transformer (two / more coils of wire wrapped around a ferrite [iron] core).
Because of this electrical isolation, you really want to separate out the secondary side 0v, Vcc- or ground connections because they will never be at exactly the same zero volt potential as the primary side because of the load characteristic trying to reduce the potential differences between the two wires when under electrical load. ...... its this electrical isolation that means that the are not true "ground" voltages but can be offset slightly which will lead to some current flow
Lots of people just join them all together and in some cases link them to the earthing point which makes it even worse.... because it can create earth leakage currents.
There is a bit of waffle over here on the UK earthing arrangements..... basically although the nomenclature is UK based, if you consider the wiring arrangements it kind of covers every possible permutation of the incoming earth....
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj2o6ycm9DPAhXKJsAKHZUuDeMQFggfMAA&url=http%3A%2F%2Felectrical.theiet.org%2Fwiring-matters%2F16%2Fearthing-questions.cfm%3Ftype%3Dpdf&usg=AFQjCNGgVmZa42MaWWheFH0je93n2TQVdg&sig2=12kT_2cmztOW93h4-zaNaA&bvm=bv.135258522,d.d24
Because cnc systems work on lower voltages, we have step down transformers or switched mode power supplies.
Both of these allow for electrical isolation of the primary (mains) and secondary (lower voltage) sides and all use some form of transformer (two / more coils of wire wrapped around a ferrite [iron] core).
Because of this electrical isolation, you really want to separate out the secondary side 0v, Vcc- or ground connections because they will never be at exactly the same zero volt potential as the primary side because of the load characteristic trying to reduce the potential differences between the two wires when under electrical load. ...... its this electrical isolation that means that the are not true "ground" voltages but can be offset slightly which will lead to some current flow
Lots of people just join them all together and in some cases link them to the earthing point which makes it even worse.... because it can create earth leakage currents.