Drives & Controls May 2022

MOTORS n 5: Efficiency Efficiency is a significant factor and is typically indicated by an IE number. While a lower efficiency motor can be repaired and re-used – sometimes to an improved efficiency level – the Ecodesign directive governs what IE rating a new motor must have, based on the application and the wider system. IE1 is standard efficiency, IE2 is high efficiency, IE3 is premium efficiency, and IE4 is super premium. There is a significant difference in efficiency between IE1 and IE4. At a power rating of around 4kW, an IE1 motor is around 80% efficient, while an IE4 motor is around 90% efficient. That represents a halving of the losses, which can account for a significant cost saving. If a 22kW four-pole IE1 motor which runs for around 8,000 hours per year is replaced by an IE3 equivalent, the saving could be in the region of £800 per year at an electricity cost of 15 pence per kWh. 6: IP rating IP (ingress protection) defines a device’s ability to stop foreignmaterial from entering and interfering with its operation. The first of two digits after the IP represents the level of protection from solidmatter, and the second liquids. The first can range from 0 (no protection fromdust) to 6 (total protection). The second goes from 0 (no protection from liquids) to 9 (able to resist high-pressure water jets). Some manufacturers will put a motor’s bearing sizes on their nameplates (7). And they may include a temperature rating , which in our example shows that the motor can run in an ambient temperature of up to 40°C (8). The nameplate may also show the insulation class to which the motor has been wound (9). The repair standard for rotating machines states that a motor can be repaired to the same or a better insulation class, so this is important information for a repairer to have. The duty cycle may also be on the nameplate. In our example, S1 (10) stands for continuous duty and indicates that this motor has been designed to run 24/7, 365 days a year without issues – subject to scheduled maintenance. Ten duty- cycle classifications cover examples such as short-term use, intermittent duty and variable load. And the number after the ~ symbol (11) indicates the phase rating of the motor – either single- or three-phase. Motors may also include other information, such as the Ex symbol, which is applied to motors designed for use in potentially explosive environments. These motors will need to be replaced with similarly rated motors and should only be repaired by a company with the expertise and ability to repair hazardous area Ex equipment. A list of certified repair specialists can be found on the AEMT’s Ex Register, on the AEMT Web site. n Once you know what you are looking at, a motor’s nameplate is relatively simple to decode