How it works: the usual two-speed high-temperature exhaust fan at low speed in order to meet the exhaust air flow, when the fire broke out, the high temperature exhaust fan in the cabinet under the joint control of the role of automatic high speed exhaust fan fire htf to meet the needs of two-speed exhaust exhaust fan fire, while fire smoke partition exhaust pipe smoke damper and smoke damper makeup air duct smoke and no action performed makeup air, automatic smoke dampers other smoke partition double About speed motor; two-speed motor are extremely variable speed induction motor temperature exhaust fan fire, by changing the stator winding is connected way to achieve change in the rotating magnetic field of the stator pole pairs exhaust fan, thus changing the motor speed. According to the formula; n1 = 60f / p shows asynchronous motor synchronous speed and inversely proportional to the number of pole pairs, doubling the number of pole pairs, synchronous speed n1 dropped to half the original speed, motor rated speed n will drop approximately half, so changes number of pole pairs to achieve the purpose of changing the motor speed. This level of speed control method is not smooth speed control, and only applies to squirrel cage motors. Roof exhaust fans | Chen Yu-conditioning (certified) | Yongcheng exhaust fan provided by Wu Cheng Chen Yu Air Conditioning Equipment Co., Ltd. Wu Cheng Chen Yu Air Conditioning Equipment Co., Ltd. (www.wccykt.com) is a leader in Dezhou, fans, ventilation equipment, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs . Chen Yu-conditioning in leadership with the staff warmly welcome all inquiries negotiations to create Chenyu conditioning a better future.