How to select the appropriate motor control system for your pump?

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The Extended Product Approach (EPA) methodology

When it comes to build an energy efficient pumping system, the choice of the appropriate motor control system is crucial. As a response to the European Commission’s regulation on Energy using Products, the EN 50598 series proposes a system-level approach called the Extended Product Approach, to select the most efficient combination of products overall.

Figure 1 : A system-level approach for pumping installation
Figure 1 : A system-level approach for pumping installation

When designing energy-efficient pumping systems, the use of the Variable Speed Drive (VSD) to control the flow rate in variable flow applications allows to operate the pump at its Best Efficiency Point (BEP) and to avoid the energy loss associated to a throttling valve. Although a VSD is often an energy efficient solution for variable flow applications, it should not become an automatic reflex.
For example, in constant flow applications the use of Direct-On-Line starter with a properly sized Premium Efficiency motors (IE3) leads to the most energy efficient solution. With such a system, there is less loss during the nominal operation of the pump and no consumption of the motor starter during the stand-by phase.

Figure 2 : D.O.L motor control + valve versus VSD motor control
Figure 2 : D.O.L motor control + valve versus VSD motor control

The essential idea is that the choice of the motor control system shall be based on how well the resulting Extended Product matches the requirements and duty profile of the application.


How to apply the EPA to pumping system?

Looking at pumping systems, the system-level analysis is a 3 step process:

Figure 3: EPA for pumping system
Figure 3: EPA for pumping system

The first step is to identify the nature of the flow of your pumping installation (either constant or variable). Secondly, if you are dealing with constant flow situation you must determine if water hammer will be an issue. Now you are in position to choose between Direct-On-Line starter, Star-Delta starter, Soft starter or Variable Speed Drive. Finally, you can start to build your pumping system with the appropriate motor control solution and avoid over-sizing

As a result, the Extended Product Approach allows you to optimize the choice of the motor control system in order to ensure a high energy efficiency level for your pumping system.

For details, case studies, and further discussion, you can read the Control Panel Technical Guide on this topic «How to select the appropriate motor control system for your pump?», or leave a comment below.


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  • Nice Article! Thanks for sharing this.

    • Benoit Leprettre

      7 years ago

      You’re welcome, glad you enjoyed it!

  • Your article is very good. Thank for share

  • Water is a primary source of every homes and business. Choosing the right motor control system to maximize the pumping and will minimize energy consumption is a good type of asset to every business. With the right choice we can avoid purchasing more water pump to supply our business or home.

  • Thanks, Andrea! This article answered all my questions.

  • It’s interesting to learn more about pumps. I didn’t realize that the Variable Speed Drive was used to make pumps as efficient as possible. There are so many things that use these pumps, so making them efficient all around is a great idea.

  • Benoit Leprettre

    6 years ago

    It is definitely a great idea to make pumps (or any other load) as efficient as possible. Just note that, as the article emphasizes, the usage of a VSD does not BY PRINCIPLE improve the overall efficiency of the pump system.

    The most important factor for efficiency is that the components of the system be suited to the application requirements and properly sized. If the application does not require varying the flow, then using a VSD may turn out to be counterproductive due to extra losses produced by the VSD: a carefully sized starter-based solution would be more efficient.

    This is why it is important to conduct the Extended Product Approach to allow comparing solutions in terms of Energy Efficiency on a fair basis.

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