Capital Equipment News August 2019

TOTAL COST OF OWNERSHIP – HIGH VOLTAGE MOTORS

“For instance, the capital cost of a 110 kW motor is about R66 000, and within five weeks, the motor would have consumed R71 000 worth of electricity. Over a five-year period, the end user would have paid about R4,1-million in electricity consumption costs. That scenario best explains why efficiency matters when it comes to motors.”

David Spohr, business development executive at Zest WEG Group

TALKING POINT

on a specific existing application. We can offer a new motor which fits on an old footprint, but we can also recommend that the customer considers the modern way of doing things – the motor-VSD combination. This is for applications where you need to control the speed of the motor or the flow of air or liquid required,” explains Spohr. He reasons that there are tangible cost savings to be made with a matched WEG motor and VSD combination. Long-term reliability and efficiency of energy use are the result of a truly compatible motor and VSD combination. VSDs are said to be probably the best method for controlling motor speed in response to varying process demands. VSDs take the fixed-frequency AC supply and convert it to a variable- frequency AC supply. This controls the power use and mechanical power output so that the motor can run at the most efficient speed for the process. The control of the motor speed can be based on feedback from the process, for example, flow rate, temperature or pressure, so that process control is improved. As a result, small decreases in the speed of pumps and fans can lead to large decreases in energy consumption. According to ScienceDirect’s research paper, Energy Management Principles , using a VSD to reduce the speed of an AC motor by 20% could reduce the energy consumption by around 50%. “The WEG motor-VSD combination significantly reduces annual running costs. When it is replacement time, don’t just replace the motor, but consider replacing it with an upgraded version of what is available on the market right now. At Zest WEG Group, we have new technologies available that can help end users save on their energy costs, and ultimately reduce their TCO,” concludes Spohr. b

the operation of motors beyond their design lifetime means that end users keep on repairing their old machines at a much higher cost. Customers tend to keep repairing the old gear, finding comfort in the belief that maintenance is an operational expense. However, if one looks at the cost of repairing the motor repeatedly, say over three years, it may amount to the cost of buying a new, efficient motor. Spohr says the cost of a major HV motor overhaul or repair, for example, is generally about 60% of the replacement value. “Customers tend to do continuous repairs on their old motors, but never consider the value of their maintenance and repair costs. There is also need to be aware of the replacement value of the motor, versus the cost of repairs,” says Spohr. If a motor is burning out on a regular basis, it is a trigger point to make a replacement decision. “One needs to consider the actual amount of money they have already spent on repairs, which is normally quite substantial, as well as the money they have lost through downtime. When you get to a point where you constantly repair a motor, there is need to consider replacing it with a new motor, which effectively reduces risk and maintenance costs, while increasing efficiency.” Modern way Commenting on old generation motors, Spohr says many old pump and fan application motors are started in a very old-fashioned manner because technology wasn’t available or considered expensive at the time of installation. The required flow of air and liquid was controlled via mechanical ways – an old and inefficient way of doing it. With the establishment of its HV equipment division, Zest WEG Group now offers WEG motor-VSD combinations. “We can walk into a factory and do an audit

would have paid about R4,1-million in electricity consumption costs. That scenario best explains why efficiency matters when it comes to motors,” says Spohr. When it is procurement time, Spohr reiterates that the upfront capital cost of a motor should be no big factor. “It’s the cost of running the motor that really matters. The most common problem in Africa is that many people tasked with procurement duties do not understand this concept. They will buy a motor that is 2% cheaper, but not considering the efficiency, which has a direct impact on the total cost of ownership, which in turn is the difference between profitability and stagnation,” adds Spohr. Spohr’s views are corroborated by a paper entitled Policy Guidelines for Electric Motor Systems , which shows that only 2% of the total lifecycle cost of an electric motor is attributable to the initial purchase price, and some 97% represents the energy costs used to power the machine. Therefore, the efficiency of the motor, its reliability and its correct sizing for the application, are all critical factors in achieving maximum efficiency and minimising the costs of operation. Maintenance costs Another important factor when it comes to the operation of HV motors is maintenance costs. Spohr reasons that

CAPITAL EQUIPMENT NEWS AUGUST 2019 14