The Association of Electrical and Mechanical Trades (AEMT) recently produced a guide outlining the total cost of ownership (TCO) of electric motors. Its aim of this motor TCO guide is to help users to understand the lifetime operating costs of their motors and how to lower them. Surprisingly, the initial cost of a motor may account for less than 3% of the total cost of ownership!
Your motor’s TCO
A motor’s TCO includes several factors aside from the initial cost. They include costs for installation, running, maintenance, replacement parts, downtime and finally, its end-of-life scrap or resale value.
There are clear financial and environmental benefits to reducing the TCO of a motor. The TCO calculation is as important for legacy motors as it is for new installations.
Variable Speed Drives
In many older motor-driven systems, it was common to oversize the motor for the duty it performed. In this case, additional dampers or throttling valves control the flow rate of fan and pump loads. Yet they unnecessarily waste energy and introduced adverse side effects, such as shortening a motor’s life.
Introducing a VSD automatically controls the flow rate by reducing the speed of the motor to match the demand. Moreover, the physics of motor operation means that power consumption reduces at the cube of the speed reduction.
For example, reducing the speed of the motor by 20% results in a 50% reduction in the power consumed. This gives a significant energy cost savings and improves the motor’s operational life with smoother starting and stopping. Other benefits include improved process control, managed start-up and stop procedures, and power quality management.
Improved Efficiency Motors
In most cases, the classification of motor efficiency is by an IE rating. IEC standard 60034-30-1 defines four classes covering 2, 4, 6, or 8 pole motors with rated outputs up to 1000kW.
IE1 is Standard Efficiency, IE2 is High Efficiency, IE3 is Premium Efficiency, and IE4 is Super-premium Efficiency. Many motor manufacturers also produce motors that meet the proposed IE5 class, labelled Ultra-Premium. However, in the UK new motor installations between 75kW and 200kW must meet the IE4 efficiency level. Motors up to 75kW and over 200 kW must be IE3 unless they have VSD control.
Significantly, many motors in service are low-efficiency models manufactured before the introduction of the IE rating. It is generally cost effective to replace these with energy efficient IE3 or IE4 types.
Other Considerations
Proper installation, setup, and ongoing maintenance are essential when looking to minimise the motor’s TCO. Bearing failure is widely regarded as accounting for around 50% of all motor breakdowns. This is often the result of poor lubrication, electrical erosion, vibration or misalignment. Excess temperature, which can damage a motor’s electrical insulation, is another common cause of failures, as is the ingress of dirt. Proper installation and setup can ensure that a motor starts life without these issues.
Condition Monitoring
Now widely available, condition monitoring solutions can perform constant measurements across your motor installations. They will provide early warning of problems and allow the taking of timely countermeasures.
Contact our technical support team to discuss how we can help with variable speed drives, motor TCO and condition monitoring in your facility.
