There is a clear trend in nearly all markets to change from shaded pole and standard AC-motors towards high efficient EC-motors which allow speed controllability. A huge number of important features make EC-motors beneficial within many applications. For menkind it becomes in future even more mandatory to save energy and natural resources. Because of that the economy is committed to make an active contribution to environmental protection.
Benefits of the EC-technology
• Efficiency of motors is up to 90% (short pay-back time by significant energy savings).
• Variable speed adjustable by analogue and digital inputs or serial interface like MODBus.
• Possible option: temperature-control, constant flow- or pressure systems.
• Connection of sensors, e.g. temperature, humidity, pressure.
• alarm relay or tach-out signal for speed monitoring.
• Long service life (brushless DC, use of semiconductors)
• Integrated protective functions e.g. locked-rotor protection and protection against incorrect connection.
• soft start and soft commutation (no anti vibration mounting needed)
• EC-motors show the same characteristics independent from the frequency of the power supply (50Hz or 60Hz)
Figure 1: exploded view of the EC-motor
Principle of the EC-motor
Figure 2: coil
The EC-motor consists of coils, e.g. 3 pairs If the direction of current is changed the magnetic direction will change as well!
When the coils of the EC-motor are placed with power they induce a magnetic field. But being able to run the motor, they need to induce a magnetic field which is rotating. This rotating magnetic field is achieved by the electronics commutating the winding currents of the stator. The correct commutation of the electromagnets can only be guaranteed if the micro-controller knows the exact position of the rotor being equipped with permanent magnets. Hall IC sensors have the task to identify the position of the rotor and to communicate the information to the micro-controller. The rotor follows the rotating magnetic field.
Figure 4: explanation of transistors
Transistors are semiconductor devices used to switch electronic signals. The function of transistors is to control large currents on the [Collector] by using a small stream on the [Basis]. This effect is needed as the micro-controller operates with small voltage and currents. The set of transistors on the ebm-papst electronics enforcing the signals of the micro-controller are called power module.
Rotation and slip
The EC-motor runs without any slip !!! An AC-Motor needs a slip to magnetise the rotor. The EC-motor doesn’t need to magnetise the rotor i.e. transfer energy through the airgap, because it includes permanent magnets. This benefit makes the EC-motor much more efficient than the AC-motor.
Efficency of the EC-motor
There are different motor principles showing different characteristics with regard to efficiency. In this comparison chart you can see – single phase AC capacitor motor with maximum efficiency between 60% and 70% – three phase AC motors showing an efficiency of about 75% – and finally EC showing a motor efficiency ranging between 80% and 90% (motor + electronics combined) – last but not least there are AC shaded pole motors with efficiencies between 20% up to 30%. The use of these motors is restricted to 30W shaft power only. The other motors provide 500W shaft power each. Behaviour at partial load: Looking at the impeller load, the load is reduced with the third order of the speed, for example at half speed there is only an eighth of power consumption, that is 12% of nominal value. At partial load the efficiency is reduced compared to nominal conditions – with AC technology the efficiency it is reduced considerably, whereas EC-technology only allows a minor drop of efficiency.