When we say ‘EC’, what springs to mind?
When talking about ‘EC solutions’, many in the HVAC world think not only of a specific type of motor, but also of a specific type of device: a compact construction associated with high efficiency. While this is a very commonplace belief, it is not strictly speaking true. In fact, the ‘EC’ stands for ‘electronic commutation’ – a term used about brushless permanent magnet motors. Electronically commutated motors do not suffer from brush wear or arcing for the very simple reason that they do not use the carbon brush commutation generally found in DC motors.
EC motors – the best of two worlds
With this design, electronically commutated (EC) motor can be said to combine the best of two worlds – AC and DC motors – in a more efficient package. They run on alternating current (AC) power, but at the same time they are essentially permanent-magnet brushless DC motors. It is these electronics that make EC motors particularly efficient – they monitor motor functions all the time and adjust the control input to maintain high efficiency at all times. This makes EC motors a very energy-efficient choice for controlling fans. And their speed can be adapted to match demand, creating even greater potential for energy savings. OJ Electronics uses field oriented sensorless control: the permanent magnet motor gives out a signal that allows us to determine the need for torque.
EC does not mean ‘integrated’
It’s no wonder that EC solutions are very popular for driving fans. They are quite rightly associated with great efficiency. And they are indeed widely used in integrated units where the motor and fan are part of the same compact construction. But this does not mean that ‘EC’ equals ‘compact’ or ‘integrated’. It is perfectly possible to enjoy the benefits of the highly efficient EC motors while combining the other elements – fan, drive, etc. – separately. And in many cases, it is better to mix and match.
Let us consider a practical example.
In an integrated construction based on an EC motor (what many think of as an EC solution), you will find that in order to make the construction as compact as possible, the motor actually reaches into the impeller’s intake area.
That makes the fan less efficient. And if fan efficiency drops from, say, 65% to 63%, the entire system becomes less efficient. You don’t get the full benefit of the EC motor’s efficiency.
By combining the parts yourself, you take the motor out of the impeller’s intake area. The fan is allowed to perform with greater efficiency, making the entire system more efficient. This approach lets you optimise each part, making the most of the EC motor’s inherent efficiency.
The takeaway
- ‘EC’ doesn’t necessarily mean ‘compact’. And compact is not necessarily best
- If efficiency is your main priority, you will often do better by steering clear of integrated options, instead combining efficient EC motors with efficient fans, drives etc.
Efficiency may not be only reason to look beyond integrated EC solutions. See more about our Fan products here.
There are many other cases where separating the individual elements makes sense – such as when you need to handle hot air from kitchens, etc. Putting the drive outside of the air flow allows the system to handle hotter air than if you use an integrated solution. And you still benefit from the EC motor’s efficiency.
Obviously, having drives placed outside the motor facilitates easier access for service staff. And it also means that the motor unit can be physically lighter, directly impacting the dimensioning/scaling of the suspension required.
Preben Jessen, Head of Drive Products, OJ Electronics
