The two MOSFET body diodes are in opposition and the MOSFETs are off, so there aren't any conduction paths available for current to flow. It will be as if the coil segment has been isolated from the circuit.

With the make-before-break arrangement I doubt the coil would see any reverse voltage anyway, since the magnetic field is not going to be collapsing.

Reply to  #429
Today at 07:07 AM

Great questions.
Short answer: with back-to-back MOSFET "AC switches" on both rails,
the body diodes do not provide a freewheel path when the gates are OFF.
You must hand-off the current (MBB) or give it a clamp/snubber.

What to do in our SS-Linear setup:

Always use MBB: next coil ON before current coil OFF (1–3 µs) so current has a continuous path.
Provide a clamp for E-stop / faults (when a coil is opened):
RC snubber across each coil (what we specified): 0.22–0.47 µF film + 10–33 Ω, ≥250 V placed at the coil terminals.
Optionally add a bidirectional TVS across each coil or each AC switch: choose a standoff above your bus (e.g., 150–200 V for a 100 V bus) and well below MOSFET Vds rating so the TVS conducts long before the MOSFET avalanches.
Keep gate timing symmetric on Tᵢ and Bᵢ; don't leave one rail on while the other is off unless that's a deliberate decay mode you've tested.

EXCELLENT!!

Thank You Both, @kampen & @lfarrand!!

All my questions answered, promise I will not be interrupting any more!!...(except when I do not understand...)

This development is just awesome!!

It FULLY guarantees the UNISON switching to be VERY SOLID, as it is the SAME CIRCUIT POWERING the GATES of the TWO Bidirectional Switches per each Coil!!..no "miss" here!!

And you are completely right, with an MBB is much less chance of any reversals through the moving Field.

Regards

Ufopolitics

Thank you for the kind words 🙏
Let's finish strong — and then let's light this thing up ⚡🧲🔥

Small update. Member @kampen and I have come to an arrangement for the fabrication of 14 AC MOSFET switches using Infineon IMZC140R038M2HXKSA1 SiC MOSFETs.



I've placed the order for the components with DigiKey and will proceed to assemble the switches once they've been delivered. After assembly I will test each one and then ship them over to @kampen.