For braking, look at the two wires that power your motor- remove power and
short those two motor wires together. That works most simply with a DC motor.
For AC, it gets more complex.
Imagine a double pole double throw (DPDT) relay wired to the motor with the
common wires each going to one of the motor wires. The NC contacts (normally
closed) would go to the power wires from the driver to the motor. The NO wires
would be shorted together.
Now, when the braking relay is not engaged, each wire runs to the motor as
it normally would. When the braking relay is activated, the two wires feeding
power to the motor are disconnected and the two wires from the motor are shorted
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