Okeydokey, we're in one of those shadowy pockets in the rules now

When we wrote the rules we envisioned that the Magneto-static Projection Barrier, as it is a continuous effect, required an Arc Generator to power it. The power required for the radius of effect being too much for a portable steam dynamo. We also saw it as being something that stayed static.
We did not imagine that someone would want to 'raise shields' on a Walker

There's nothing as devious as bloody players!
Note that the only other electric device on a Walker is the option for an Arc Cannon on the Kaiser Wilhelm. The Steam Dynamo on this does crank up its capacitor recharger, however, it can only fire every other turn unless within the radius of an Arc Generator.
NB: The Magneto-static Waistcoat and Umbrella run off integral batteries.