Description of the problem

For the Malaysia Metro project, four Huawei OSN devices are deployed in the customer's central server room at the Subang depot site, and the four OSN devices are connected to the same DC power cabinet.

The customer's power supply cabinet can support a maximum current of 54A, while our four OSN devices have reached a current of 48A during normal operation. The customer was concerned about whether the expansion of our equipment would lead to excessive current, which in turn would cause the power supply to trip. The customer asked Huawei to provide a general formula for calculating the impact of single-board expansion on the power supply side current, so as to guide single-board expansion.

Alarm Message

None

Processing

For example, in the OSN3500 to expand the capacity of a SLD16 single board, and the normal power consumption of this single board is 23W, then we can probably calculate that if the equipment expansion of this single board, and the power supply cabinet to bring the amount of change in the value of the current: 23W / 38.4V, that is, about 0.6A change. Thus, we can conclude whether the expansion will exceed the maximum current limit of the power supply cabinet.

Root cause

1: Our transmission network equipment generally only has requirements for the size of the openings in the customer's power cabinet, such as OSN3500 enhanced subracks have different requirements for 32A, 64A openings, and does not describe in detail how to calculate the current on the power supply side of our equipment when configured with different veneers;

2: through consultation, find information, the R & D gave the following calculation: in the comprehensive consideration of voltage drop, power supply instability factors, the current generated by the device A = sub-shelf all the single board rated power consumption / 38.4 V. That is to say, the power supply cabinet side of the current A is approximately equal to the sub-shelf inserted into the total rated power consumption of the single board divided by a fixed voltage of 38.4 V. (This value is not reflected in the product documentation), this value is an empirical value, which is determined by the product documentation. (This value is not reflected in the product documentation, but is an empirical value, recommended by the fixed network structure development department engineers based on their experience).

3: The 38.4V here is not equal to the actual power value measured on the sub-frame, because this value is a more appropriate value that is suitable for use in the engineering field by considering various factors.

Suggestions and Summary

Our transmission network equipment hardware guide, generally only the rated power consumption of the single board, through the above formula of the approximate calculation, we can derive the expansion of the single board can be brought to the power supply cabinet, so as to avoid excessive current, resulting in the power supply cabinet tripping problem, to ensure the success of the expansion.

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