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HERE 1.0 MEASUREMENT CHARACTERISTICS
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HERE 2.0
DEFINITION OF CHARACTERISTICS
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HERE 3.0
MECHANICAL INSPECTION
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HERE 4.0
ELECTRICAL INSPECTION
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HERE 5.0
ENVIRONMENT
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HERE 6.0
MULTIPLE FAN USE
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HERE 7.0
FAN LIFE TESTING
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HERE 8.0 INSULATION CLASS REFERENCE
1.1
Measuring the Air Volume and Static Pressure
| Note: |
The
above diagram shows the principles required in measuring
air volume and static pressure. (The actual measurement
is provided using a computer.) Using the above mechanical
model, the "Capacitance Changing Type Diaphragm
System Differential Pressure Transmitter"
will convert the value for air volume and static pressure
in place of a Pitot tube. |
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The
equation:
*Air volume
Q=60 ×C × ×  [m /min]
C : Coefficient
of nozzle air volume
D : Diameter
of nozzle [m]
r : Air density
(1.293 × × ) [Kg/m]
t : Temperature[ ]
P : Air pressure
[mmHg]
Pn : Differential
pressure of air volume mmAq=[Kg/m]
g : 9.8m/sec
Static pressure
: ps=ps [mmAq]
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 mmH O
= 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/min
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 [M/MIN] |
| |
W
: Amount of heat generation within cabin |
| |
T1
: Temperature of intake air to cabin |
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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.
3.1
Rotation direction :
Clockwise
from the front face of the fan a Clear " "(arrow mark) shall be found
on the body of housing.
3.2
Safety design:
All fans
are engineered to prevent damage to the winding and all electrical
components during a locked rotor condition. Restart is automatic
when the obstruction is removed.
3.3
Locked rotor protection :
No damage
was found during a 72-hour test in which the rotor was locked
on an operating fan. The fan restarted automatically as soon
as the obstruction was removed.
3.4
Polarity protection :
Up to normal
polarity, no damage was found during a reverse connection test
at the rated voltage.
3.5
Vibration Test :
Vibration
tests are conducted in accordance with JIS C0040, Amplitude
1.5 mm,
Frequency 10~55Hz, 0.5 hour in 3 axes (X,Y,Z)
3.6
Shock Test : JIS C0040 Acceleration of Gravity
60G Time
= 6 msec. in 3 directions each: X,Y,Z
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., measured
with a 5mA trip current between the housing and the positive
end of the
lead 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 Determination |
| Current |
More
than 15% of initial value |
| R
P M |
More
than 15% of initial value |
| Noise |
5dB
A in excess of initial value |
| Starting
Voltage |
More
than 10% of initial value |
If any items
above exceed the levels of determination failure will occur.
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.
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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. |
 |
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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
1.0 service factor motor 1) |
Allowable
Temperature Rise
1.15 service factor motor 1) |
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) + 32
1) 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
