When sourcing a 220V DC motor speed controller, you must prioritize rated current and peak current capacity to ensure the controller can handle the motor's startup load. Look for Pulse Width Modulation (PWM) technology, which offers higher efficiency and better torque maintenance at low speeds compared to SCR-based controllers. Additionally, verify the input voltage tolerance (e.g., 180V-240V AC) and the output voltage range (typically 0-220V DC) to ensure compatibility with your specific motor type, whether it is a permanent magnet or a shunt-wound motor.