PWM Fans Eliminate Commutation Noise

The company's high frequency, pulse width modulated (PWM) fans eliminate commutation noise by switching their coils with a PWM frequency above the range of human hearing, i.e., beyond 20 kHz. Fan speed is controlled by an external PWM signal and the fan speeds up linearly from a 20% duty cycle, up to its maximum rated speed. The fans are available in sizes measuring 70 mm x 15 mm, 70 mm x 25 mm, 80 mm x 25 mm, 92 mm x 25 mm, 120 mm x 25 mm, and 120 mm x 38 mm. Prices range from $4 to $15 each depending on fan size, features, and quantity. JMC PRODUCTS, Austin, TX. (800) 580-6688.