- Are the fans of SEPA EUROPE brushless?
DC fans are always brushless. The English term “brushless fan” is often used in this context. Commutation is an electronic process and that does not require “brushes” which is the case with simple, low-priced DC motors found for example in some cordless screwdrivers or drills. AC fans do not have commutation, the torque is produced via phase shift in the motor.
- How can you change the speed of DC fans?
The speed of DC fans is controlled via the operating voltage or via a PWM input.
- How long is the service life?
EPA sleeve bearing fans have a typical service life expectation (MTTF) of 210000h and ball bearing fans of 350000h. This value refers to continuous operation at an operating temperature of 40°C and greatly depends on the temperature. Caution! When evaluating service life data always compare the specified temperatures.
- What is the difference between L10 and MTBF?
Both refer to statistical data that are determined from a large number of specimens at nominal conditions. L10 indicates the probability of failure of 10 % over „n“ hours, whereas MTBF (Mean Time Between Failure) indicates the average time between two failures that is deter-mined for a large number of specimens. As the fans as a rule are not repaired, the first error is equivalent to a MTTF failure (Mean Time To Failure). The values always refer to a specific temperature. The data contained in the SEPA data sheets are based on 40 °C https://www.sepa-europe.com/en/technische-info/fans-life-expectancy-mtbf
- Does the reduction of the speed improve the service life?
Hardly. As the bearing load is extremely low, there is virtually no wear. The service life is de-termined predominantly by the ageing of the lubricant and does not depend on the speed.
- Does switching off the fan periodically increase the service life?
No, on the contrary. Frequent switching on and off substantially increases bearing wear espe-cially with regard to sleeve bearing systems and can also result in premature failure. We rec-ommend switching off the fan if it is only very rarely switched on, e.g. in the event of occa-sional extreme temperatures.
- Are noise data contained in the data sheet an indication of the noise behaviour in the appliance?
Only partially. The values stipulated in the data sheets refer to airborne sound that is determined at a fan that has a soft suspension, free-blowing, at a distance of 1 m, taking into consideration the frequency response of the hearing sensitivity (A-evaluation) in a sound-proofed room. The conditions are completely different in the appliance. Structure-borne sound, resonances and the operating point of the fan strongly affect the actual noise development https://www.sepa-europe.com/en/technische-info/noise
- How does the change of speed have an affect on the noise?
The noise depends to a great extent on the speed. If the speed is reduced by half, the noise drops by 10-15 dB(A)! As the speed tolerance can be up to ±15 %, a noise tolerance of ±2 dB(A) and more is not unusual. With two, slowly rotating fans that are not positioned directly next to one another, one can achieve a lower noise level than with one fan that operates at a higher speed.
- What is the curve of a fan?
The flow rate of a fan depends on the counter pressure that is produced in the appliance by the air resistance. The data sheets only contain the two extreme values, flow rate without counter pressure (free blowing) and maximum pressure (flow rate 0, closed housing). Both do not reflect actual practice. In addition one finds the curve that displays the progression between these extreme values. The typical working range of an axial fan is in the range of 20 and 30 % of the maximum pressure and must always be below the saddle that is typical for this fan design. Operation with too high counter pressure (e.g. through air intake or discharge openings that are too small) increases the noise considerably.
- Are fans also available with IP55 or IP68?
- What is the difference between sleeve and ball bearings?
Sleeve bearings function according to the hydrodynamic principle. Ideally the rotating shaft swims on an oil film. Ball bearings comprise two bearing shells in which steel balls roll within a so-called ball cage. The balls are greased and the bearing shells sealed with two cover plates.
- What are the dimensions of the smallest DC fan in the range?
- Can SEPA EUROPE also provide 3D data?
We can gladly send you 3D data on request.
- Can you deliver fans with a connector?
SEPA EUROPE is specialized in customized solutions. The fans can also be delivered with all customary connectors and with various lead lengths.
- How can you mount axial fans?
- How can you mount chip coolers?
- How can you mount blowers?
- What is the better arrangement, suctioning or blowing?
There is no arrangement that is clearly better. The position must be selected so that the air can flow optimally around the critical components that require cooling. With the suctioning position, the fan is cooled by the cooler external air which increases the life expectancy. The fan can also be positioned inside the appliance and not on the outside walls. In this case the side of the appliance exposed to overpressure must be hermetically sealed off from the underpressure side.
- What is the difference between alarm and tacho output?
Both are basically output signals for monitoring the correct functioning of the fan. Malfunction results in the output signal changing which can be evaluated accordingly. The alarm output is connected with the collector of a switching transistor that switches over in the event of an error. The output is connected with a voltage source via a series resistor (pull-up). The shift from L to H in the event of an error is standard. The tacho output provides a speed-proportional rectangular shaped output signal.
- How does the tacho function?
The tacho signal is used to monitor exactly the correct operation of a DC fan. While the propeller is rotating a switching transistor is activated via the rotor magnets two or three times per revolution. The tacho output is connected with a positive voltage source via a pull-up resistor. The output supplies a rectangular shaped frequency that is equivalent to 2 x or 3 x the actual speed. If the fan stops, the output signal is permanently L or H. A true speed control can be realized via the frequency of the tacho signal.
- How does the PWM input function?
The PWM input signal modulates the voltage supply of the motor spools so that depending on the pulse width (= on-time) it is switched on between 30 and 100 %. The frequency is approx. 23 kHz and outside the audibility range.
- Can you nevertheless control standard DC fans without a PWM input with a PWM signal?
What is meant here is a pulse width modulated operating voltage. With most of the fans this functions, however, the low voltage should not drop below 2.5V, so that the motor IC is not switched off with every pulse.
- Which voltage must I provide?
The operating voltage of a DC fan can be either, 5 V, 12 V, 24 V or 48 V depending on the model. Other voltages are possible but not widespread. The tolerance of the supply voltage is ±10 %. For starting the fan, a starting current is required that is 2-3 times higher than the nominal current. The current supply must be able to supply this current. Conventional AC fans require a nominal voltage of 110 V, 230 V or 400 V and develop a speed that is proportional to the mains frequency.
- Can DC fans be electrically connected in series?
Yes, if the fans are identical models. Both fans must be protected against overvoltage via parallel switched Z diodes in case a fan bocks. Both Z diodes in series must have a higher Z voltage than the voltage supply can provide. Tolerances must be given consideration:
(Z1 + Z2) * 0,95 > UN * 1,1
Example: 2 fans for 12 V at a 24V power supply, protected by 15V Z diodes:
(15+15) * 0,95 = 28.5 > 24 * 1.1 =26.4.
The upstream Z diodes must be dimensioned so that they do not become overloaded when the fan blocks.
- Can a fan be operated with undervoltage?
Yes, up to 60% of the nominal voltage of 5V-fans and up to 40 % of the nominal voltage of 12V and 24V fans is possible. For this purpose a starting voltage of ≥ 85% of the nominal volt-age must be briefly applied to ensure that the fan starts after a longer break and low temperatures. The fan voltage be reduced simply using a Z diode or a series resistor, if an electrolytic capacitor is arranged parallel to the upstream component. The upstream component must be dimensioned so that it is not overloaded even if the fan blocks.
AC fans cannot be controlled via the operating voltage as the speed is linked to the network frequency.
- What are EC fans?
Electronically commutated AC fans with an upstream AC/DC converter are referred to as EC fans. This new generation of AC fans operate extremely efficiently, as they require considerably less electrical power compared with conventional AC fans. Further advantages are the fact that the speed is not dependent on the mains frequency and a wide-range input that is suitable for virtually all mains voltages and frequencies that exist worldwide. EC fans can be equipped with both a tacho output and a 0-10V control input https://www.sepa-europe.com/en/news/new-energy-saving-ec-fan-generation-ul-approval