[Al Skierkiewicz]

Alex,
You are correct about the back EMF working to brake the motor but the action occurs as the armature windings move withing the magnetic field of the permanent magnets within each motor. Any wire in a changing magnetic field will induce current to flow in the wire. The current flows into the very low impedance of the speed controller when in the Brake mode. As long as the motor is not spining faster than it did when being driven, the EMF generated should be about the same as when controlled. It will of course produce a current flow opposite to that when it is driven by a voltage source. There should be no real increase in generated field than that which occurs with the motor under control. The high instantaneous currents will produce some fields around the motor wiring, and these may interfere with some signal wiring. If you are not using zip type cable (the two wires are bonded to each other and the fields tend to balance out.) then the fields around the wire can be a source of interference. For that reason, do not run servo, sensor or modem cables near motor wiring