ESKOM Fact Sheet: Lower your farm’s irrigation costs with Variable Speed Drives

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Using VSDs for Lowering Costs

The electric motors that drive pumps on irrigation systems are extremely energy-intensive, making irrigation systems one of the largest consumers of electricity on South African farms.

Variable Speed Drives (VSDs) can reduce energy consumption at the pumping plant by regulating electric motor speeds to match the energy demand with the system load – whilst balancing voltage. In doing this, VSDs reduce irrigation systems’ energy consumption and contribute to lowering your farm’s operating costs.

Motors on irrigation systems often use more electricity than needed because the system design rarely requires the motor to operate at its maximum capacity which the motor will do when not controlled. This means that they run at full speed regardless of the actual output required, wasting electricity.

Installing a VSD will regulate the speed and rotational force – or torque output – of the motor to match actual demand so that it doesn’t work faster than it needs to.

Centrifugal pumps on irrigation systems are variable torque applications, which offer the highest potential to save power. Reducing the speed of the pump by a small amount will result in a massive reduction in the amount of energy used because pumps are governed by the Affinity Law of Power α (Speed)3. Slowing down a pump from 100 to 80% can reduce a motor’s energy use by up to 50%.

In the case of an irrigation system where various sizes of land are irrigated using the same pump, a VSD can be used to adapt the speed according to the respective water and pressure requirements of the various sizes of land, instead of having the motor running at full speed and all the excess energy being dissipated by the pump’s pressure regulator or throttle valve.

For the full ESKOM fact sheet, please download the document from the EMHEATER website at: LINK

For more information regarding VSDs, please refer to the following related blog posts:

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