Brake rectifiers convert AC Voltage to DC Voltage which is required to energize the magnet or coil of every DC brake. Rectifiers are Available in 4 pole and 6 pole (which includes a switch) designs. Rectifiers are rated for a maximum voltage and amperage. Rectifiers are paired to the motors based on Brake Coil Voltage and AC Supply voltage.
Bridge Rectifier a/k/a Full Wave Rectifier ( example: 230 VAC supply to 205 VDC Brake coil )
The bridge rectifier consists of diodes and varistors that filter undesirable voltage spikes and enable fast current shutdown. The DC supply provides higher speeds and more reliable brake operation. Bridge rectifiers offer smoother DC supply than a half wave rectifier. In a bridge rectifier, the two halves of the sin wave equate to about 90% throughput of the input voltage.
Half Wave Rectifier ( example: 230 VAC to 103 VDC )
The half-wave rectifier works in that it only allows the positive portion of the AC sin wave and smooths out the voltage in between the waves. This allows a single polarity voltage to reach the brake. A half-wave rectifier allows 45% of the input voltage to pass through
Fast Excitation Rectifier.
Fast-acting rectifiers work to help the brake become energized faster and release the motor quicker. Fast Excitation Devices allow for a sudden jolt of voltage (~90% of inbound feed) to pass through but then after a few milliseconds switches to allow approximately 45% of the input voltage.
AC Brakes are also offered by many vendors. No rectifier is required for their operation.