Voltage inverter, freewheeling and regenerative breaking

[Alexandre_Borowczyk]

I’m trying to get a better global understand of how the whole systems works. One thing that get me confused is what is the the voltage inverter? I’ve looked at the schematic at the end of the user manual for the sapog firmware and the FET are connected to V_bat but at the beginning of the document it written as inverter volatgae supply.
The document mentions as well the inverter being turn off in freewheeling, what does that means exactly?

Lastly in the regenerative breaking section they talk about
‘Typically, the controller’s hardware is equipped with some protection circuits that activate and dissipate the excessive energy when Vinv increases a certain threshold;’ what does that look like normally?

Really appreciate the help!

[pavel-kirienko]

I’m trying to get a better global understand of how the whole systems works. One thing that get me confused is what is the the voltage inverter?

A three-phase voltage inverter is a circuit composed of six transistors pairwise (or an integer multiple of six if they are connected in parallel or, rarely, mostly in older designs, in series) where each pair uses pulse-width modulation to generate a particular average phase voltage. You will find more info at https://en.wikipedia.org/wiki/Power_inverter.

I’ve looked at the schematic at the end of the user manual for the sapog firmware and the FET are connected to V_bat but at the beginning of the document it written as inverter volatgae supply.

It’s the same thing. Conventionally, the inverter supply voltage is denoted Vbat.

The document mentions as well the inverter being turn off in freewheeling, what does that means exactly?

It means that all six transistors are permanently closed. When turned off, the inverter may still conduct through the anti-parallel diodes.

Lastly in the regenerative breaking section they talk about
‘Typically, the controller’s hardware is equipped with some protection circuits that activate and dissipate the excessive energy when Vinv increases a certain threshold;’ what does that look like normally?

Usually, it’s a set of TVS (transient voltage suppression) diodes, possibly with a braking resistor. You can find an example on the schematic here (the three diodes next to the power input): How I Learned to Stop Worrying and Love ESC Development

[Alexandre_Borowczyk]

Hi Pavel,

Thanks very much for the information.
Regarding the freewheeling, with the current firmware is it active of passive freewheeling?

[pavel-kirienko]

Regarding the freewheeling, with the current firmware is it active of passive freewheeling?

The firmware implements active freewheeling. If the inverter is turned off, however, it’s passive, but this mode is not used normally, as you can see in the description.

[Alexandre_Borowczyk]

Alright I understand better! And in the sapog software when does freewheeling is applied vs regenerative braking?