DC-Bus generation in inverter modules

[LPaandi]

These days, there are many inverter modules such as this -

https://www.electro-tech-online.com/custompdfs/2013/01/FNB41560B2.pdf

This Fairchild datasheet and other similar products claim that their intended application is small power consumer motor drives like washing machines and ACs.

What I'm curious about is how the DC bus would be generated in such a system? Is it just a diode bridge? Would the DC bus have to be isolated from the household 120VAC?

The reason I started thinking about isolated DC is because I'm assuming the digital ground (the buttons, keypad interface and other UI) would have to be chassis (earth) grounded at some point. In the case of these modules, the digital ground and the dc-bus negative are electrically not isolated. Wouldn't it be a NEC violation to ground the DC-bus negative?

Thanks!

 

[Diver300]

The DC bus would normally be generated by rectifying the 120 V supply. However it is possible to have a 60 Hz transformer followed by a rectifier. That is what is done in audio amplifiers.

For all the digital connections, either all the insulation is rated to more than 120 V, the signals to and from the power converter are isolated. It is a lot easier to isolate a few low power signals than kW powers.