2OverviewLeonardo Evolution units offer the possibility to choose between two different types of Backward Curved Fans:Standard Asynchronous Fans on T**R units;Brushless Electronically Commutated Fans on T**V units.Brushless electronically commutated fans lead to the greatest benefits.
3OverviewEC (Electronically Commutated) fans, basing on “Brushless” technology, create substantial advantages in terms of:Lower Running costs compared to the traditional backward curved fans;More flexibility on the adjusting of fan speed basing on the real needs of the aeraulic circuit;High performance with low noise, thanks to a particular shape of this last generation impeller;Starting current lower than nominal current;Continuous fan speed regulation from the microprocessor;Integration, thanks to the possibility of interfacing with the AFPS and Active Floor System.
4General InformationIn any motor, either the rotor or the stator, must have a rotating magnetic field in order to cause the motor to turn.This rotation can be accomplished by:Three-phase AC power;Single-phase power with some sort of circuit element like a capacitor, inductor, or resistance to synthesize a second phase (that is timed differently from the first);An electro-mechanical commutator to switch power to different coil groups as the motor turns.
5General InformationThere are limitations with each of the previous methods:Three-phase AC power is not available everywhere and the frequency and voltage are constant, making the speed control difficult.Single phase power has all the characteristics of three-phase power. In addition, phase-shifting methods produce a very imperfect rotating field, tend to introduce considerable losses in the motor and produce a very weak starting torque.An electro-mechanical commutator solves several of the above problems. It can accomplish wide-range speed control, and it can provide high starting torque. The limitation is that the electro-mechanical commutator has friction and wear problems that reduce efficiency and require frequent maintenance.Also, a voltage controller has to be used to accomplish speed control.
7General InformationElectronic commutation potentially eliminates all the previous problems. Power is pulsed on and off electronically with semi-conductor devices; the pulsed signals power three or more circuits or coil groups within the motor.By varying the timing and duration of pulses, the electronic controller can accomplish speed control and maintain high torque at start and over a broad speed range.Power SupplyPermanent MagnetsCoils
8General InformationThe EC motor is equipped with periferal permanent magnets and internal electromagnets which are electronically commutated.The commutation is made by a power transistor, therefore there are non mechanical elements such as a collector of brushes which would noticeably reduce the life.In EC motors the magnetic field is generated by the same rotor thanks to the presence of permanent magnets. The commutation of the magnetic field is electronic and consequently free of wear and tear resulting from contact between static and rotating parts.The operating mode and the materials used lead to an increased efficiency which is shown in less absorption with the same performance.
9Advantages of the EC motor BRUSH DC motorit requires carbon brushes to commutate (drive) the motorlimited operating hours, few 1000hBRUSHLESS DC motor (EC motor)no carbon brushes requiredextremely long service life, commonly over hStartup Current = 3.5 x Nominal CurrentStartup Current < Nominal Current
10Basic Principles of the EC motor With the EC motor, the magnetic field is generated in the rotor itself by permanent magnets.Commutation is electronically and therefore without wear-and-tear.Depending on their layout and the application, EC motors can be operated from:the DC power supplyvia an external / integrated commutation unitdirectly from an AC mains supply.
11Characteristics PWM (pulse width modulation) EC motors are controlled via PWM or linear (0-10 Vdc) input signal. There is an open loop speed control so that the speed changes depending on the load.Closed loop speed control is possible with integrated electronics.There are inputs for potentiometers, 0-10 Vdc or PWM signals.PWM (pulse width modulation)A PWM signal is a square wave signal with a variable pulse-pause ratio.Linear closed loop /open loop speed controlAt 0 Vdc, the motor is de-energised and does not rotate. From 1 Vdc onwards, the motor starts to run. Maximum speed is reached at 10 Vdc.
12Electrical Specifications Input voltage range: VACFrequency: 50/60 HzInput power: max. 3kWProtection: IP54Control input kΩAmbient temperature: -20 bis +55°C-20 bis +60°C with cooling
13Electrical Connections This is how the EC fan can be connected to the driving circuit.As told before the main ways to control it is through the PWM or the 0-10V signalOther ways (not used) are controlling the load (temperature) or at full speed or through a potentiometer.
16Why using an EC fan?The power input of an axial fan in EC technology is compared to that of an axial 3-phase fan in figure 3,With three different control modes used.In the maximum air flow range, the EC motor requires 15% less power input than the 3-phase motor, which is due to its better efficiency.When it comes to lower air flow values, especially in the partial load range, then the advantage of the EC technology get even more pronounced. This is simply due to the fact that the EC motor has a high efficiency across a wide speed range, whereas the efficiency of the 3-phase motor quickly drops with decreasing speed.Power input in the partial load range is more than 50% lower than what the 3-phase motor requires.Based on an average annual operation time of 4,000 h/a and the power saving , the annual saving in costs by simply using an EC fan can be calculated easily.
17Why using an EC fan?Whenever a 3-phase fan is operated with triac control or frequency converter, the noise behaviour in the partial load range gets negatively influenced.This is illustrated, and comes as a result of the oscillations in the electromagnetic fields and deviations in electric conductance which form electro-magnetic harmonics with their resulting power and torque excitations.The fan emits them in the form of air-borne or structure-borne noise.So far, and from an acoustic point of view, the most harmless case has been operating a 3-phase fan with a transformer.The same positive noise behaviour can now be achieved with EC fans, with phases and their time sequence being impressed in a suitable way.
18Why using an EC fan?Electronically commutated motors also allow the advantages of “soft start” which means lower inrush currents compared to nominal values.The voltage range is much wider than that which is available for traditional motors and due to a 0-10V input these fans can be regulated continuously.This means that the speed can be selected from the user terminal or may be integrated with the AFPS which can vary the speed based on the static pressure present underneath the floor.
19FunctioningThe Hall effect IC is a solid state electronic device with no mechanicalparts and therefore it is more reliable than a reed switch.To no surprise it is now the most widely used sensor in industrialbrushless motors.Normally, however, they include a lot of other componentsWhen magnet #1 gets close to the Hall IC, the sensor sends a signal to the base of thepower transistor.The transistor opens, and allows a bigger collector current to flow through theelectromagnet.The electromagnet pushes magnet #3 away.
20FunctioningWhen the rotor spins away, magnet #1 stops affecting the Hall IC.Since the signal to the base of the power transistor has been removed, it is turned off.This disables the electromagnet.The rotor continues to spin due to inertia until magnet #2 moves into the workingrange of the Hall IC. The Hall IC sends a signal to the base of the transistor. The transistor opens, and allows a bigger collector current to flow through the electromagnet. The electromagnet pushes magnet #4 away. This process continues until the power is disconnected.