What is an energy efficient motor?
What is an energy efficient motor? Please briefly explain the criteria that distinguishes an energy efficient motor from a non- energy efficient motor.
Well the short and simple answer is the amount of heat (and to a smaller extent noise) a motor gives off. However leaving the answer here is insufficient and further consideration needs to take place when comparing the efficiency of a motor. On motor data sheets the efficiency is normally expressed as a percentage of power in v’s power out.There are some common mistakes made here however, the one I see most is when an engineer will look at the power out as the rated wattage of the motor and compare this to the power in by using ohms law. There are however many pitfalls with this approach. The output power is mechanical (π/30.M.n) and the input is electrical (V.A). You would think this could be directly compared off a motor data sheet, but it cannot. The reason being is that some manufacturers will pick a different loading point for the output mechanical power. Companies that are very conservative will give an output power level that the motor can achieve 24/7 others that are slightly more liberal on the data sheets will give peak power levels. I have even seen hobby motors that use the speed constant as a power rating so one must be careful when interpreting supplied data.
What factors should manufacturers and designers consider when assessing if their motor(s) are energy efficient?
Primarily one should consider the design principal and the quality. Some motors by design are more efficient than others. For example; If a motor contains a laminated stack then eddy currents which represent a loss are generated within the iron laminations. From a design standpoint you can select an Ironless motor to eliminate this loss altogether or from a quality standpoint you can select a motor with very thin iron laminates and higher grade metals to reduce this eddy current loss.
There are a huge number of additional factors here like bearing type and quality, the air gaps within a motor the type of magnets and so on. The key here is really to find a supplier with the expertise and support to guide you through the options with respect to the application
Improving motor efficiency: How can manufacturers go about getting a non-compliant motor(s) to meet energy efficient standards?
Often it is too late to apply a band aid solution if the motor is already in application. The most gains to be made here are on the controller side. If speed, torque or position control are required for the application there are newly released controllers on the market with over 95% rated efficiencies.
The main loss is however in the conversion of electrical to rotary and the mistake made most often here in Australia is a result of familiarity. An engineer with a machine to build will select the motor he knows and has always used. Sticking with something you know is eventually going to mean you are not going to be using a motor design with the latest advancements. I couldn’t count the number if times I have seen manufacturing equipment with large AC motors moving tiny loads. 90% of the energy consumption is going into turning the motor itself. Or the number of times we receive a call from someone who asks for a 1HP motor or even worse asking for a 10 or 20A motor without knowing the efficiency or the load requirements! There are motors available that meet and exceed the highest global efficiency standards we just need engineers to be mindful of this during the selection process.
What are your thoughts on the energy performance standards in Australia for motors – are they too low/high? Please explain whether they are realistic and achievable, and if manufacturers are meeting them.
I am a little biased here because my standpoint is commercial. maxon supply very high quality motors with ironless designs and extremely high power density rare earth magnets. Higher efficiency standards are going to put our products in higher demand. The real issue is as I mentioned before. If you have a 1Kw motor rated at 98% efficiency it will satisfy any guidelines in it own right. Though if you only need a 100w motor to move your load you have wasted a whole lot of energy through poor product selection.
What is the demand like for energy efficient motors? Please briefly explain if you are seeing an increase/decrease/flat line in demand for energy efficient motors?
Though I am still considered a “whipper snapper” in the industry, I have been working with electric motors for over 24 years now, in my early days rewinding large AC units but almost 15 years now with maxon. During this time there has been a steady increase in the efficiency of motors and a huge increase in that of motor controllers. However this has not come about in my opinion from purely an energy saving desire. It has come about through the application requirements. Robotics, aerospace, defence and medical science applications to name a few and particularly solar and battery powered devices have required smaller, faster, stronger motors, gearheads, encoders and drive electronics. It is the extreme application requirements that lead to an overall improvement in technology and therefore efficiency.
What energy efficient motor options does maxon motor offer in the local market?
If you were to look at pure efficiency, our rare earth high grade neodymium DC motor range in brushed and brushless is what we offer. We do still have Alnico and Ferrite ranges that are cost effective by comparison and use an ironless design that is still much more efficient than most of the traditionally designed laminated stack motors.
Can you briefly describe an example where an energy efficient maxon motor was used to replace an inefficient one, and what the benefits were?
We are constantly replacing large AC motor installations with DC gearmotor systems to reduce size noise and power consumption when a customer is going through a design review or equipment upgrade but by a large margin the replacement for efficiency gains is that of stepper motors. Stepper motors are often very noisy and have a mechanical detent that restricts them from being able to achieve linear and efficient movement profiles. CNC machines in particular often have steppers fitted for their great cost effectiveness. This makes them a profitable option to design into a machine most often exported for sale. We are constantly having the steppers replaced by servo’s. So often in fact there are even local companies arriving on the scene that manufacture motor controllers to take step and direction in and give servo out. Therefore I would say that the replacement of inefficient motors with new efficient motor designs is an entire market in itself.
Is there anything which you wish to add that was not covered For engineers who would like to know more about motor efficiency and design?
maxon have a complete education department called maxon academy. They offer texts, online tutorials and training courses on all aspects of mechatronics. The information and training is not maxon specific and covers all relevant motor, gearing, sensor and control technologies. The texts and tutorials are currently being used by many education departments within Australia and worldwide. You can find a link to the maxon academy from the maxon motor website.