16. Fan PWM-to-speed mapping
This section describes the mapping between fan pulse width modulation (PWM) and expected speed in revolutions per minute (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 low-speed fan rotor. The high-speed fan rotors are named with a “0” suffix, for example “fan2_0”, while the low-speed fan rotors are named with a “1” suffix, for example “fan2_1”.
Note
The fans are numbered 1 to 5 in the hardware, but 0 to 4 in the software. The fan numbered 1 in the hardware corresponds to fan0 in the software. See Fan numbering in the Pod Maintenance Guide for more information.
Note that the fans are mechanical devices that will have slightly different mechanical characteristics that lead to some deviation in expected fan speed. The maximum allowed mechanical deviation is shown in Table 16.1. The software will allow a maximum deviation of 20%.
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 |