16. Fan PWM to speed mapping

This section describes the mapping between fan PWM and expected speed in RPM. The IPU-Machine has five fan modules, named “fan0” to “fan4”. Each fan module consists of two fan rotors, one high speed fan rotor, and one lower speed fan rotor. The high speed fan rotor are named with even numbers, such as “fan0_0”, while the low speed fan rotor are named with odd numbers. Note that the fans are mechanical devices that will have slightly different mechanical characteristics that leads to some deviation in expected fan speed. The maximum allowed mechanically deviation is shown in the table below. The software will allow a maximum deviation of 20 %.

Table 16.1 Fan PWM to expected speed mapping

Fan type

PWM [%]

Expected speed [RPM]

Mechanically allowed deviation [%]

High speed

40

9150

+-5

Low speed

40

7990

+-5

High speed

50

12193

+-5

Low speed

50

10576

+-5

High speed

60

15616

+-5

Low speed

60

13512

+-5

High speed

70

18934

+-5

Low speed

70

16433

+-5

High speed

80

21658

+-5

Low speed

80

18906

+-5

High speed

90

25264

+-5

Low speed

90

22179

+-5

High speed

100

28516

+-5

Low speed

100

24813

+-5