High-efficiency electrical motor manufacture High-efficiency electrical motor manufacture | HBM

Selecting correct test equipment benefits high-efficiency electrical motor manufacture

China's 'Plan For Improving Motor Efficiency'

Manufacturers of electrical motors increasingly need to find effective ways of testing their latest designs as pressure grows to develop more energy efficient models. Energy conservation and emission reduction are increasingly important to national governments and industry because electric motors consume more than 40% of the world’s total power consumption. This accounts for over 60% of industrial electricity consumption making energy saving through improved motor efficiency an obvious choice.

High efficiency motors are mandatory

As part of this drive many countries have set minimum energy consumption standards (MEPS) and are making the move to using high efficiency motors mandatory. A quick look at the figures involved underlines the necessity for this change.

A high efficiency motor has an efficiency of between 2% and 8% per cent better than a standard motor. This means the electrical energy savings in China would be 76.5 billion kWh for a whole year if the efficiency of all the electrical motors in the country were increased by 5%; this is similar to the 2008 generated energy output of the world’s biggest hydropower station, the Three Gorges Hydropower Station.

There are a number of international standards that electrical motors need to comply with depending on where they are being deployed. The relevant standard in China, GB18613, has been frequently updated, with GB18613-2006 becoming effective in July 2011. A more recent standard, GB18613-2012, came into force from September 2012, and the latest standard, GB2, will be implemented in a further three years.

Energy savings of 80 billion kWh

China has recently produced a national “Plan For Improving Motor Efficiency (2013-1015)” as a further indication of the importance of high-efficiency motors. The plan wants 50% of low-voltage three-phase cage asynchronous motors and 40% of high-voltage motors to meet the standards of high-energy efficient motors by 2015. The plan seeks to promote an accumulative increase of 170 million kW in high-efficiency motors while eliminating 160 million kW of inefficient motors currently in use. In addition the plan would implement 100 million kW in energy savings through technical reconstruction and 20 million kW in savings through remanufacturing of eliminative motors to high- efficiency standards. China expects to achieve energy savings of 80 billion kWh by 2015. This is equivalent to saving 26 million tons of standard coal and 68 million tons of carbon dioxide emissions.

One of the most important areas of testing: Torque measurement

Many companies are now increasing their research, development and manufacture of high-efficiency motors to conform to these new mandatory standards and expectations. These development programs demand rigorous testing of multiple parameters to establish that any new designs meet – and possibly exceed – the requirements of the relevant standards.

One of the more important areas of testing is in torque measurement and in many cases there is more than one approach. HBM has a number of different solutions to suit customers’ individual needs.

T20WN torque transducer

For example, HBM’s T20WN torque transducer measures static and dynamic torque and rotation speed or angle for turning or static machine parts. It is designed for measuring small to medium torques, such as are found on performance or function test benches for domestic or business machines. The T20WN has an integrated bearing that allows it to be fitted as a support bearing and simplifies handling as well as featuring electronics with a ±10 V output signal.

T40B digital torque transducer

By contrast the T40B digital torque transducer can measure static and dynamic torque on rotating shafts. In addition, the torque transducer is equipped with a magnetic speed measuring system. Test beds can be extremely compact because of the short construction of the transducer making it suitable for a very wide range of applications.

Chinese regulations require that instrumentation used to measure torque is accurate to ±0.2% of full scale while instrumentation used to measure frequency needs an accuracy of ±0.1% full scale. Speed measurements must be accurate within 0.1% or 1 revolution per minute whichever gives the least error.

With HBM’s T40B series the temperature impact TC 0 and TC span is 0.05%/10K (50Nm = 0.1%/10K) and in most motor test applications there is little temperature change so the focus is more on linearity and repeatability. This means that HBM’s T40B torque transducer can ensure an accuracy of better than 0.2% full scale while taking into account the most important parameters.

In addition the T40B torque transducers are available with different ranges - 5kNm, 1kNm, 200Nm, 50Nm – so that they can easily meet the requirement for torque sensors with accuracy 0.2% full scale for motor tests. This saves costs while the simplified installation makes maintenance much easier.

The T40B features an output pulse count of 1024 pulses/revolution from 50 Nm to 10 kNm, covering all measuring ranges. The magnetic rotational speed measuring system with high output pulse count allows precise measurement of rotational speed, especially at low rotational speeds, to give reliable measured values.

Structure of electric motor test stands

Test specimens (electric motors) in test stands require frequent installation and disassembly. Sometimes, operators even need to exchange torque sensors and dynamometers. Therefore it is essential that test stands allow easy mounting, dismounting and aligning.

The below picture show an example of an electric motor test stand:

Signal conditioning solutions

Consideration must also be given to the data acquisition and subsequent signal conditioning in addition to measuring torque to derive the most accurate information from any tests. HBM has a number of solutions including the PME range of products that offer different types of signal conditioners for recording of all measured quantities relevant to processing, such as force, displacement, pressure, temperature, speed, frequency and torque.

The PME system is based on a modular design enabling measured signals from different transducer types to be conditioned uniformly. All modules come with an LCD display, keypad, CAN interface, and various additional devices for optimizing the signal.

An alternative is the PMX that is HBM’s latest data acquisition and signal conditioning system for use in production control and industrial test benches. The PMX gives precise and reliable results by enabling the professional acquisition of force, torque, vibration, pressure, strain, temperature, voltage, current and many other quantities. The PMX has 16 measuring and 32 calculating channels with each channel rated at 19,200 samples per second. This means that the PMX can manage up to 400,000 values per second. The PMX also supports real-time communication via Industrial Ethernet and has modern browser based user-software and flexible plug-in cards.

The whole measurement chain and full service

HBM is able to help its customers by offering the whole measuring chain, including transducers, measurement electronics, software and services. HBM has developed professional and powerful data acquisition software for configuring, visualizing and analyzing measurements such as torque, rotating speed, phase voltage, line voltage, power, power factor, and frequency.

HBM can take full responsibility for all measurement tasks, including applications consulting, technical support, training and seminars, repairs, calibration, and spare parts with solutions widely used throughout the motor industry while our excellent service provides added confidence.