Any reason why you chose high-side braking over low-side?
Brake-current goes up to 15A (measured with 20cm wire) for 300mS,
Current limit (on lowside, 2 SMD-resistors with 40% margin @5A
@Tamb=70°C) is set to ~5A So the current limiter would interrupt
braking, which doesn`t happen when braking with highside-fets.
Presumably the motors have high enough DC resistance that this
is a sufficient loss mode for braking,
It`s an old mechanical design with some new electronis inside. To keep
the old sensoring my customer decided to brake the motor some 100ms
before the slider reaches the mechanical stoppers. So this "hard"
brake helps to reduce mechanical stress at the stoppers. The FETs
(IRFR3410) can handle these currents without problems and the sliders
don`t crash as hard as with the previous design...
so back EMF doesn't cause over-current in the FETs.
Did you consider using regeneration instead?
Yes, but much to dangerous for this design as there is no load or
capacitor which can handle the back-EMF so voltage would rise to an
unknown level...
hth