Engineering Data
1.0 SOFASCO FAN CHARACTERISTICS ARE MEASURED AS FOLLOWS:
1.1 Measuring the Air Volume and Static Pressure
The Equation
Maximum static pressure:
As shown in the above figure, when closing the nozzle, the pressure in the "A" chamber will reach its maximum. The differential pressure, (Ps) between the air pressure and the pressure in the "A" chamber is the maximum static pressure.
Maximum air volume:
When opening the nozzle and absorbing the air using the auxiliary blower to make the static pressure equal to zero (ps=0), the differential pressure (PN) between the "A" chamber and the "B" chamber will reach the maximum. The air volume obtained by applying the differential pressure (PN) to the above equation is called the maximum air volume.
CONVERSION CHART
STATIC PRESSURE
1 mmHO = 0.0394 inch HO
1 mmHO = 9.8 Pa
1 mmHO = 25.4 mm HO
1 Pa = 0.102 mm HO
1 inch HO = 249 Pa
AIR FLOW
1 m/min = 35.31 ft/min(CFM)
1 CFM = 0.0283 m/min
1 m/min = 16.67 l/sec
1 CFM = 0.472 l/sec
1 l/sec = 0.06 m/min1.2
1.2 Performance Point:
The Performance Point is the point at which the system impedance curve and the air static pressure curve intersect. The Performance Point equals the air volume (throughput) of the fan when the fan is operating. The Performance Point Curve is as follows:
1.3 Determination of Air Volume:
The following formula should be used to calculate Air Volume:
Q=40W/(T2-T1)
| Where: | Q: Required air volume [M3/MIN] |
| W: Amount of heat generation within cabin | |
| T1: Temperature of intake air to cabin | |
| T2: Temperature of exhausted air from cabin |
1.4 Noise Level Testing:
Acoustic noise is measured in a semianechoic chamber by means of a B&K precision integrating sound level meter with a background noise level below 20dBA. The fan is operating in non-resistant air with a microphone at a distance of one meter from the fan intake.
Sound pressure level (SPL) which is environmentally dependent and sound power level (PWL) are defined as
SPL = 20 log10 P/Pref
and PWL = 10 log10 W/Wref
where P = Pressure
Pref = A reference pressure
W = Acoustic power of the source
Wref = An acoustic reference power
Fan noise data is usually plotted as Sound Power Level against the octave frequency bands.
The measurement standard is according to : CNS 8753
2.1 Rated current:
Rated current is measured after five minutes of continuous propeller rotation at a rated voltage.
2.2 Rated speed:
Rated speed is measured after five minutes of continuous propeller rotation at a rated voltage.
2.3 Start Voltage:
The voltage required to start the fan after it has been switched on.
2.4 Input power:
Input power is measured after 5 minutes of continuous rotation at a rated voltage.
2.5 Locked current:
Locked current is measured within one minute of rotor lock-up (after 5 minutes of continuous rotation at a rated voltage in clean air).
2.6 Air volume & static pressure:
The air volume data and static pressure is determined in accordance with the AMCA standard or the DIN 24163 specification in a double chamber test with intake-side measurement.
2.1 Rated current:
Rated current is measured after five minutes of continuous propeller rotation at a rated voltage.
2.2 Rated speed:
Rated speed is measured after five minutes of continuous propeller rotation at a rated voltage.
2.3 Start Voltage:
The voltage required to start the fan after it has been switched on.
2.4 Input power:
Input power is measured after 5 minutes of continuous rotation at a rated voltage.
2.5 Locked current:
Locked current is measured within one minute of rotor lock-up (after 5 minutes of continuous rotation at a rated voltage in clean air).
2.6 Air volume & static pressure:
The air volume data and static pressure is determined in accordance with the AMCA standard or the DIN 24163 specification in a double chamber test with intake-side measurement.
4.1 Insulation resistance:
More than 10,000,000 ohm between the housing and the positive end of the lead wire (red wire) at 250 V.D.C.
4.2 Dielectric strength:
No damage detected at 500 V.D.C 60 sec. or 600 V.A.C. 2 sec., measuredwith a 5mA trip current between the housing and the positive end of thelead wire.
4.3 Life expectancy:
The expected average life for a fan not designated as an Extended Life fan running at the rated voltage and in continuous operation at an ambient temperature of 25ºc and a humidity level of 65% is 50,000 hours. If any of the conditions listed below are met or exceeded, premature failure will occur.Item Level of DeterminationCurrent More than 15% of initial valueR P M More than 15% of initial valueNoise 5dB A in excess of initial valueStarting Voltage More than 10% of initial valueIf any items above exceed the levels of determination failure will occur.
| Item | Levelof Determination |
| Current | Morethan 15% of initial value |
| RP M | Morethan 15% of initial value |
| Noise | 5dBA in excess of initial value |
| StartingVoltage | Morethan 10% of initial value |
4.4 Insulation Class:
A Class
5.1 Operating temperature:
-10 ~ +70 (normal humidity)
5.2 Storage temperature:
Satisfactory performace standards after 500 hours of storage at -40~70(normal humidity)with 24 hours recovery period at room temperature.
The following figures show the performance characteristics for parallel and series operation of two identical fans.
Parallel Operation
An additional fan in parallel to the first increases airflow in a low static pressure situation.
Serial Operation
An additional fan in series increases the airflow in high static pressure enclosure. .
Life expectancy of a cooling fan is a critical element in thermal design. SOFASCO uses parametric failure modes during life testing to calculate for life expectancy. Speed(RPM) and Current (mA) failures include both "hard failures" (where the fan is non-functional) and "parametric failures". These parametric failures are defined as 15% decrease in RPM and 15% increase in current than initial.
Including parametric failure modes leads to a more conservative L-10 and MTTF reporting standard than those methods that measure life performance using only hard failures.
SOFASCO evaluates fan life and reliability during the design phase using accelerated life testing in conjunction with ORT (Ongoing Reliability Testing). Accelerated life testing is used to compress the amount of time required to conduct life testing. Development testing occurs early in the product design, prior to product release. It is vital to characterize the reliability of the product in the initial stages of design to allow for improvements and to meet the reliability specifications prior to release to manufacturing.
Once the design has been through design verification testing and is turned over to manufacturing. ORT is conducted. The value of ORT is a continued refinement of the accuracy of the accelerated life testing and constant review of the design of the fan. This continued process improvement allows for ongoing evaluation and increase in fan life and reliability.
Under accelerated life testing, SOFASCO fans are tested at extreme environmental conditions, with temperature stress factors above standard operating levels. In order to gather meaningful data within a reasonable time frame. The stress factors must be accelerated to simulate different operating environments. High temperature stress is the most common stress factor used for these purposes.
Proper understanding of accelerating stresses and design limits are necessary to implement a meaningful accelerated reliability test. SOFASCO uses the Arrhenius model for determining acceleration factors (AF) during life testing. This is the most commonly used model in accelerated life testing where thermal stress is the primary factor affecting life.
Life test data gathered from different type of fan lends to highly accurate statistical analysis. This data can produce very detailed information about the behavior of the product for reliability and prediction of fan performance in the field. The Weibull Distribution is a typical method employed by SOFASCO for which 10% of a population will have failed and 90% of a population will continue to operate within specifications.
Insulation systems are rated by standard NEMA (National Electrical Manufacturers Association) classifications according to maximum allowable operating temperatures as follows:
|
Temperature Tolerance Class |
Maximum Operation Temperature Allowed |
Allowable Temperature Rise at full load |
Allowable |
|
|
oC |
oF |
oC |
oC |
|
|
A |
105 |
221 |
60 |
70 |
|
B |
130 |
266 |
80 |
90 |
|
F |
155 |
311 |
105 |
115 |
|
H |
180 |
356 |
125 |
- |
· T(oF) = [T(oC)](9/5) + 321)
Allowable temperature rises are based upon a reference ambient temperature of 40oC. Operation temperature is reference temperature + allowable temperature rise + allowance for "hot spot" winding. Example Temperature Tolerance Class F: 40oC + 105oC + 10oC = 155oC.
In general a motor should not operate on temperatures above the maximums. Each 10oC rise above the ratings may reduce the motor's lifetime by one half.Temperature Tolerance Class B is the most common insulation class used on most 60 cycle US motors.
Temperature Tolerance Class F is the most common for international and 50 cycle motors