Permanent Magnet Cooling Tower Motor

A permanent magnet (PM) cooling tower motor is a high-efficiency, variable-speed, direct-drive motor designed specifically for cooling towers. These motors use permanent magnets in the rotor instead of induction windings, making them far more efficient—especially at low speeds—when paired with a VFD.

Here is a clear, concise explanation focused on cooling-tower use:

✅ What a Permanent Magnet Cooling Tower Motor Is

A PM cooling tower motor is a direct-drive, inverter-duty motor that:

* Drives the fan without a gearbox or belts

* Uses permanent magnets to produce the rotor field

* Runs only with a VFD (cannot be started across the line)

* Provides high torque at very low RPM, ideal for cooling tower fans

They are quickly replacing traditional induction motors + gearboxes.

Advantages of Permanent Magnet Motors on Cooling Towers

1. Much higher efficiency

* 5–20% more efficient than induction motors

* Huge savings at low/moderate speeds where towers run most of the year

2. No gearbox required (direct drive)

* Eliminates gearbox oil

* No alignment, no intermediate shaft

* Very low maintenance

3. Quiet operation

* No gearbox or belt noise

* Smooth, vibration-free speed control

4. Excellent low-speed torque

Start heavy cooling tower fans easily and softly, reducing mechanical stress.

5. Better in harsh environments

* Lower operating heat

* High moisture protection coatings

* Can be sealed or TEAO/WPI/WPII type

Drawbacks / Considerations

1. Higher initial cost

Motor + VFD is more expensive upfront.

2. Must use a compatible VFD

Only VFDs with sensorless PM or permanent magnet control modes work.

3. Replacement and repair are specialized

Requires PM-capable shops for service.

4. Fan removal often required

Because most PM systems are direct-drive, the fan hub must come off the shaft for replacement.

Top Manufacturers of PM Cooling Tower Motors

ABB / Baldor

* RPM-AC PM cooling tower motors

* Direct-drive upgrade kits for Marley & BAC towers

US Motors (Nidec)

* “Vertical Inverter Duty PM Motor” line

* Drop-in options for tower upgrades

WEG

* Permanent magnet direct-drive HVAC & cooling tower motors

Marley (SPX)

* HP7000 Direct Drive PM Motor System

* Integrated motor + VFD package

EVAPCO

* PM direct-drive fan systems in AT, PMT, and eco-series towers

Regal / Marathon (ECM/PM motors for HVAC)

* Used in select direct-drive tower applications

Where PM Motors Are Typically Used

* Energy-saving upgrades from gearbox systems

* New towers with VFD control

* Industrial or commercial sites running 24/7

* Noise-sensitive environments (hospitals, campuses, offices)