60 V 200 A isolator contacts wearing
Snubbers are a rather vague collection of multi-variable designs. {polarity(s), voltage, current, power, energy}
AC and DC snubbers are different designs.
Although mechanical switches, relays or (large current) Contactors in small DC motors &lt; 1Hp are largely obsolete, the snubber designs to protect the switch are unique.
The mechanical switch in air when turned off must arc in order to extinquish inductive current as the contact gap starts small when it opens and therfore MUST arc (unless moving at impossible speeds of 1 us faster than ionization)  The decay time of current depends on the voltage rise to the clamp voltage during when it is high impedance then the low impedance clamp of the TVS being Rs , Tau=L/R until the current drops below the arc holding current just like an SCR in principle.
When the motor inductive surge voltage T=L/R drops below the back EMF or generator voltage, the snubber current is zero and the motor coasts to a stop from friction.
A speed brake with be a short circuit or pulsed brake or an electronic PWM controlled switch to control the rate of de-acceleration demands a lot of energy to be absorbed but stops quickly.
here's a tutorial on R, RC , TVS snubber designs.
modus operandi
First define your design goals (SPECS) for control of motor and protection of switch in measurable terms. Then think about design questions to ask yourself.
https://assets.nexperia.com/documents/application-note/AN11160.pdf