Improvements in industrial motor design fosters efficiency in factories
Industrial systems all over the world rely on electric motors for their operation. Growing demand for lightweight, energy-efficient motors is placing pressure on engineers to ensure the correct balance between quality and performance.
In 2011, ABB estimated that there were 300 million industrial electrical motors in use worldwide, and predicted a future growth rate of 10 per cent annually. Such high growth can be put down to increased use across sectors, including automotive powertrains, office and household equipment, aerospace and the renewable energy market.
With wide use comes high consumption. Nearly half of the world’s 22,000TWh of electricity consumption comes from industry, and of that two-thirds is used by electric motors. Any energy saving in motor design and development, therefore, will have wide-reaching significance.
ABB estimates that improvements in design can increase the efficiency of individual motors by up to 30 per cent, while the European Union has said that more efficient motors can be expected to save an average of €700 throughout their product lifecycle. It estimates that more efficient motors could save Europe around 135TWh of electricity by 2020.
Efficient motor design not only saves energy consumption, it can also contribute to reduced weight and size, which may make systems integration easier. With messages of sustainability and efficiency out there, hardware and software suppliers are working to develop energy-efficient models by designing and testing motors, inverters and drives, and those products using them, in order to meet the growing demands of industry.
The connected factory
Renewable technologies, with their production of varying amounts of energy from day to day, are driving ‘energy productivity’ – that is, doing more with the same, or less.
“Industry needs to be more flexible when it comes to consuming energy to account for days with less energy,” says Charlotte Nicolaou, software marketing engineer at National Instruments.
According to Nicolaou, with the rise of the Industrial Internet of Things (IIoT) or Industry 4.0, where the connected factories share data for management and maintenance, power-monitoring systems will play an increasing role. Such systems will keep track of the energy consumed to show when a component needs to be replaced because it is using too much power. Timely replacement, or maintenance before a repair is needed, can reduce downtime as well as save energy.
National Instruments reports a shift from testing new products with motors, drives and inverters to a hardware-in-the-loop system, in which hardware simulates the motor and sensor environment in real-time. Signals are sent to the inverter or drive under test, allowing the products to be developed faster and at a lower cost.
“Real-world tests are more expensive, and with a hardware-in-the-loop set-up, we can test how an inverter interacts with a motor, while we are developing the real motor,” Nicolaou says. “By implementing energy-efficient systems, such as power monitoring, you can discover other potential inefficiencies within the system. Once they have been identified, you can then go about fixing them and improve the throughput of the factory. If your energy-efficient system is monitoring the hardware’s power consumption, then it can also do some basic analysis of the hardware.” For example, it may observe a spike in power consumption and send an alert for an engineer to fix the problem before it causes the whole production line to shut down unexpectedly.
Earlier this year, National Instruments introduced the latest version of its systems engineering software, LabVIEW 2017. New toolkits include one for open platform communications (OPC) united architecture (UA), for client-server safety and maintenance communications and management. Another new feature is channel wires for field programmable gate array (FPGA) code development.
“One big trend we are seeing is the use of FPGAs for motor and drive design,” says Nicolaou. “An FPGA can provide exactly the right amount of power at exactly the right time to control motors and drives. They can also implement algorithms to reduce noise and harmonics created. By better controlling the motors and controlling the power factor, companies can save a huge amount of money by preventing penalties from the grid operator. LabVIEW allows us to design the algorithm and then directly deploy it to the FPGA hardware,” she explains.
The channel wires allow developers to communicate quickly and simply between two parallel pieces of code on an FPGA. The FPGA can be used in the design and testing of any device where fast or predictable processing is required.
The latest version of the software also has the FPGA IEC 61131-3 interface utility. Using this, FPGAs can connect with embedded devices to integrate and deploy the International Electrotechnical Commission (IEC) standard, allowing design and maintenance teams to collaborate using a standard interface. LabVIEW also has toolkits for machine learning to help with predictive maintenance, and toolkits for power monitoring.
Monitoring performance and efficiency within motors can also be used to improve overall product design. Test and measurement company HBM has bundled a power analyser and a data acquisition (DAQ) system into one product, the eDrive, to allow for efficient machine analysis. The product has one of the highest accuracies available, at 0.02 per cent, says HBM applications engineer Omer Mir, and is large enough to accommodate up to 50 separate inputs, rather than the conventional four to eight. Use of such systems not only accelerates the analysis test process but also eliminates synchronisation issues, as all signals are timed on the same clock and with the same timestamp.
Using DAQ systems, electric motors can be monitored to ensure efficiency, checking and logging results from multiple channels. Rises in temperature, inrush currents, and any vibration changes that can affect the efficiency of the motor are all monitored. Engineers can monitor three or four signals as well as physical conditions, such as temperature and vibration changes. Overlaying these signals provides a profile of what factor, or factors, affect efficiency.
These results characterise a motor, but more importantly, says Mir, the data shows you how the efficiency is achieved. “It gives you all the data leading up to the number,” he says. “How did you get to that number? It tells you how, over the stages, you get to the efficiency percentage. Traditionally, analysers will tell you the loss, and therefore the efficiency, but [eDrive] really gives an insight into motor behaviour – how it is reacting at each set point in its range.”
Multiply the data collection for three, six and 12-phase motors, which are increasingly common, and the test time is extended significantly. Voltages and currents, together with physical parameters, such as vibration and temperature, have to be examined in each phase of the motor.
The data provides an insight into the behaviour of the motor and how it reacts to different set points. This allows the engineer to tweak the inverter controlling the motor to keep it in a ‘sweet spot’, and make sure it stays within its most accurate band, says Mir.
Another aid is an efficiency map – a 3D diagram generated by the power analyser. It shows the efficiency bands of the motor where the most loss occurs. If the motor only operates in the most efficient band, efficiency can be optimised.
To meet the needs of various motor environments, from dynamic motors, where there is constant acceleration, braking, ramping up and ramping down, to motors for automotive, aerospace and the electrification of trains, a set of modules is available with eDrive. These card modules slot into the eDrive chassis to make the system configurable. Voltage, torque, current, speed and angle are default measurements, explains Mir. There is a single module to cover temperature, vibration, pressure and strain, and one to examine an inverter’s frequency switching at a higher sample rate. This looks at the inverter and its switching operation as well as the motor input/output.
For Anoop Gangadharan, product marketing manager at Yokogawa Test & Measurement, maximising efficiency through test is all about power and frequency switching. He notes that the trends for energy efficiency and component miniaturisation result in electronics using wider bandwidths and increasingly adopting high-frequency switching circuits.
“This creates the need for high-accuracy measurements, taking high-frequency performance and harmonics into account,” he says. “With increasing electrification of the powertrains, this will hold true for applications using motors and drives too.”
Gangadharan notes that power analysers which integrate software are now replacing power meters. These can automatically carry out compliance tests against standards in harmonics or standby power.
“Motor design in the automotive, robotics, industrial automation and renewable energy industries requires multi-channel analysis of electrical parameters,” he says. “In addition, it requires analyses of mechanical parameters, such as synchronous speed, mechanical power, electrical angle and rotation speed and direction, for an holistic assessment of overall system efficiency.”
For this reason, Gangadharan says, Yokogawa’s WT1800 power analyser has six measurement channels and a motor evaluation function. The universal meter can be used to evaluate inverter and motor characteristics in hybrid and electric vehicle design, and to gauge energy-saving design in data centres, printers, copiers, refrigerators and heating, ventilation and air-conditioning (HVAC) systems.
To accommodate the various speeds required for motor testing, the analyser supports a lower limit frequency of 0.1Hz for harmonic analysis at low rotational speeds and analysis for high-frequency components up to 500th order of 50/60Hz.
Direction-sensitive capabilities measure and integrate instantaneous power in positive and negative cycles. This allows, for example, the measurement of battery charging and discharging used in hybrid and electric vehicles.
As the increase in numbers of motors, drives and inverters continues apace around the world, the need for energy-efficient design becomes more pressing. It is vital that the increase in volume does not lead to a correspondingly large rise in energy consumption.
The continued development of hardware and software offerings will ensure that the power demands can continue, without impacting global energy supply.
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