Electric Motors:
Primary movers of exhaust fans.
Guided by alternating current electric motors, mostly induction motors.
Supplied with 240 or 480 volt power.
Larger motors may include soft starters to decrease electrical stresses during startup.
Motors may have multiple speed capabilities for flow control.
Drive Systems:
Connects the motor to the fan, determining impeller rotation speed.
Types of Drive Systems:
Direct Drive:
Used on smaller blowers.
Lower cost, fewer components, reliable.
Requires little maintenance, suitable for small spaces.
Fan is connected directly to the motor shaft, moves at the same rotations as the motor.
Belt Drive:
Used in larger blowers.
Capable of handling large amounts of air.
Fan linked to the motor with a belt, driven by a belt and motor pulley.
Fan rotation is proportional to motor rotation.
Allows easy modification of RPM by changing drive size.
Enables separation of motor from fan for challenging environments.
Motor Speed Control:
Speed may be varied or constant using two techniques.
Variable Speed Drives (VSDs):
Control motor speed by changing input voltage.
Used with both AC and DC motors.
Benefits include precise control, reduced energy consumption, and lower startup power requirements.
Variable Frequency Drives (VFDs):
Control motor speed by changing voltage and frequency.
Only used with AC motors.
Benefits include improved ventilation and indoor air quality, energy efficiency, and lower maintenance costs.
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