Thursday, 10 December 2015

Dave Hawley, ABB's UK General Manager for motors & generators writes: In many cooling tower applications the sustained low speeds required for operation are generally achieved with an AC motor, a gearbox, shaft couplings and bearings.

This setup is used so that only the gearbox itself is in the air stream of the cooling tower, making it the only component that has to stand up to the heat and humidity found in these applications.

However, a gearbox is an expensive piece of kit that needs additional protection against the operating environment in a cooling tower to operate reliably. There are other pitfalls to be wary of too, as the supporting components required including the couplings, bearings and motor increase overall component costs.

The use of these mechanical components also introduces areas where possible failure could occur, and increases the risk of production outages should any of them fail.

One way to get around this to increase reliability, eliminate failure risk and lower overall component acquisition costs is to fit an ABB direct drive RPM AC motor-drive package and replace the gearbox altogether.

Can you really change a gearbox and all of its accoutrement with just a motor and variable-speed drive? I hear you ask. The answer is, absolutely you can, provided you select the correct package.

The ABB motor-drive package for cooling towers comprises an ABB permanent magnet motor with an ABB industrial drive, ACS880. The ABB drive is used to establish an optimum speed set point and allows a trickle current to flow to the motor to prevent the cooling tower fan from wind milling when not in operation.

Together, the motor and drive combination delivers precise fan control without the need for a gearbox, even under low load or speed conditions often experienced in cooling tower applications. This completely removes the need for mechanical components for the cooling tower drive train setup and eliminates the potential failure risk and operational maintenance costs that would normally be incurred.

ABB’s RPM AC permanent magnet motor has a high power and torque density ratio which is needed to achieve the sustained low speed required for cooling tower operation. It is designed to retrofit into existing gearbox footprints within the cooling tower to allow swap-out in less than six hours.

The motor has a low temperature rise, thereby providing cooler running that extends its life. Eliminating the gearbox from the cooling tower system increases efficiency levels as the power from the motor is transferred directly to the fan with virtually no losses.  Typically energy savings greater than 10 percent can be achieved through the elimination of the gearbox, with greater savings achievable through the speed control of the fan when the cooling tower is at lower load levels.

To find out more about how an ABB direct-drive motor drive package can help you eliminate gearbox failure and lower overall operating costs, call the ABB motors team on 07000 MOTORS, that’s 07000 668677

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