Electricity + Control March 2021

DRIVES, MOTORS + SWITCHGEAR

Beyond the VSD: Making motors run efficiently Motor efficiency is often overlooked completely when industrial companies are addressing energy saving and the associated reductions in operating expenditure.With a focus on chemical companies, TonyYoung, Director of CP Automation, a UK based specialist in the service and supply of drives, controls and resistors, presents top tips for ensuring the motors in a plant run as efficiently as possible.

A complex cost-saving game Electricity costs are rising as global demand continues to grow, making it imperative for industrial companies to con- tain electrical usage. Those companies that do invest time and money in energy reduction seldom go beyond fitting variable speed drives (VSDs), or tackling tariffs to save on price per kilowatt hour. However, there are a host of ad- ditional measures that can be addressed with very little capital expenditure and they all result in long-term profit by reducing overhead costs. Highly complex plants, like chemical plants, face sig- nificant technical challenges: from the integration of many different energy sources to maintaining a wide array of en- ergy conversion systems, and the need to use by-product energy effectively. For example, hydrogen is created as a by-product from the manufacturing of chemicals like chlo- rine. This can be captured and transported for use else- where, or used to help power the chemical plant itself. Choose the right motor upfront One of the first steps should always be to ensure you are fitting the right size of motor for the respective application in the first instance, whether this is for pumps, fans or com- pressors. A good provider of motors, controls or VSDs will always offer an audit first, which will help you achieve this. Design engineers tend to over specify ‘for tomorrow’, but for plant and maintenance professionals this just means higher energy bills. Furthermore, if you plan to add a VSD now or later as a retrofit product, ensure that the motor is VSD rated to start with, otherwise any retrofit project will involve replacing the motor as well. Over specification also raises maintenance bills. I have seen countless motors, which are doing an easy job like water pumping for example, specified at a much higher ca- pacity than required. Sometimes this is to the point that the motor installed costs twice as much as one that could do the same job effectively. I have also known motors to be sent in for an overhaul with problems on parts of the motor that are not being used at all. When the situation is reported to the customer, they

Beyond fitting VSDs, there are a number of other steps plant engineers can take to ensure motors run efficiently and reduce energy usage. are completely unaware of it because it’s a problem with functionality they did not need in the first place! As a clear analogy: you wouldn’t buy a mini bus for a family of four. Keep it simple if you can The less complex the motor, the better. From a repair per- spective, if you can use a standard energy-efficient motor, which you can switch on and have spin at the right speed with no bells or whistles, then use it. It will be cheaper to install, there will be less to go wrong and if something does go wrong, the repair will likely be easier and cheaper. Choosing a high efficiency motor is not always a given in every application, particularly if someone in the buying chain is looking at only the initial capital expenditure of the application and not the equipment’s long-term running costs. However, with the European Union’s Ecodesign Directive in place we should see fewer end users specifying low efficiency equipment. In addition, opting for simplicity is not always possible. In some instances there is the need for a timing device or soft

Electricity + Control MARCH 2021

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