ABB SAFT125CHC Chopper Control Board: Dynamic Braking for AC Drives

The ABB SAFT125 CHC (also styled as SAFT125CHC) is a specialized chopper control board manufactured by ABB for its AC drive systems. It functions as the intelligent controller for a brake chopper unit, a critical component for managing regenerative energy in variable frequency drive applications. This board monitors the DC link voltage within the drive and activates an external braking resistor to safely dissipate excess energy, thereby preventing dangerous overvoltage conditions during motor deceleration or overhauling loads.

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Description

Application Scenarios:In a high-inertia elevator or hoist system driven by an ABB AC drive, the motor acts as a generator during the descending phase, pumping electrical energy back into the drive’s DC link. Similarly, in a conveyor belt rapidly stopping a loaded line, rotational energy is converted back into electricity. Without a controlled path for this energy, the DC link voltage would rise precipitously, potentially damaging drive capacitors and power semiconductors. The ABB SAFT125CHC chopper control board is the brain that prevents this. Installed in the drive cabinet, it continuously monitors the DC bus voltage. When the voltage exceeds a precise setpoint, the SAFT125CHC instantly switches on (chops) the current path to an external braking resistor. The resistor converts the excess electrical energy into heat, clamping the DC voltage to a safe level and allowing for controlled, rapid deceleration without drive faults or trips, ensuring operational safety and cycle time.

Parameter:

Main Parameters	Value / Description
Product Model	SAFT125 CHC / SAFT125CHC
Manufacturer	ABB
Product Category	Brake Chopper Control Board / Dynamic Braking Controller
Compatible Drive Series	ACS 600, ACS 800, ACS 1000? and other drives with chopper brake options
Primary Function	DC Link overvoltage monitoring and control of external brake IGBT/chopper
Control Logic	Monitors DC+ and DC- voltage, provides gate drive signals to external chopper module
Activation Threshold	User-adjustable or fixed DC bus voltage setpoint (e.g., ~810V for a 400V drive)
Control Output	Fiber-optic or electrical gate pulse to external brake chopper module
Status Indicators	LEDs for power, fault, and active braking status
Power Supply	Typically derives power from the drive’s internal control supply (e.g., 24V)
Mounting	Boardslot or DIN-rail mounting within the drive or auxiliary cabinet
Key Feature	Provides pulse-width modulated (PWM) control of braking power for smooth dissipation