[PSUBS-MAILIST] Pressure hull progress

[Sean T. Stevenson via Personal_Submersibles]

So it is an AC induction motor driven by a motor controller, or variable
frequency drive (VFD), which in this case looks like a turnkey solution
(matched motor and controller) from one manufacturer.  Typically in
industrial systems, a VFD has a rectifier stage, which converts some
incoming AC voltage (constant) to DC, and then an inverter stage which
converts the DC back to AC at the desired (controlled) frequency.  The
DC bus voltage in this case must be sqrt(2) times the desired motor
voltage, in order for the inverter to be able to supply the AC peaks.
It looks like the manufacturer you linked to is providing a custom
controller without a rectifier stage, so you supply the DC bus directly
via batteries, and it just takes care of the VF inversion.  It wasn't
clear from the available documents on that site whether you must supply
a DC voltage of sqrt(2) times your motor voltage, or if the controller
has some sort of onboard step-up transformer or DC-DC converter to be
able to achieve AC voltages comparable to the DC supply.

Sean