Permanent Magnet Direct Drive Fan Motor
Cooling Tower Parts
Brand: Marley | Product Type: Cooling Tower Parts
Direct drive permanent magnet motors are a newer technology available on most Marley NC Cooling Towers. The permanent magnet motor directly drives the fan, eliminating a number of components, including the gear drive, driveshaft, pillow block bearings and couplings, and associated installation and alignment costs.
Since 2011, SPX Cooling Technologies has offered permanent magnet motors to meet cooling tower customers’ direct drives requirements. Direct drives eliminate the need for Geareducers, couplings, or belt drive systems because the motor shaft is the fan drive shaft.
Direct drive systems provide several key benefits:
- Maintenance needs are drastically reduced. Direct drive motors only need occasional greasing providing an estimated $1,000 per year in potential savings versus gear drive for a large package cooling tower.
- Eliminating the coupling and gearbox means fewer components to align and maintain.
- Overall efficiency is improved. Though permanent magnet motors generally have a lower efficiency than standard motors, when gear or belt losses are taken into account, the permanent magnet motor can provide 1-2% efficiency gains. On larger systems this can total up to $1,400 a year in energy savings.
When electing to use direct drive for a cooling tower there are key factors to consider:
- VFDs are required for operation. Permanent magnet motors do not allow for across the line starts and must be operated via a VFD. This is also necessary since the shaft cannot be allowed to rotate backwards (which natural air flow may cause when not in operation) a VFD helps protect against this.
- Redundancy capability is reduced since a VFD bypass is not possible.
- Permanent magnet motors are considerably heavier than standard motors. Extra precautions and steps need to be taken when mounting and removing the motor.
- Direct drive systems have a much higher purchase price than standard motors and accessories. This must be taken into account for ROI calculations.