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Analysis on the Power Supply Problem on an NE40E-X8

Publication Date:  2018-09-26 Views:  150 Downloads:  0
Issue Description
The power distribution box (PDB) of the NE40E-X8 that converts AC power into DC power requires four AC power inputs to provide four DC supplies. However, the equipment room of the customer can provide only two AC power inputs for each router.
Handling Process
In the case of one AC input, the PDB provides two DC power outputs in parallel for the device. In this way, when two AC inputs are available, the PDB provides four DC power outputs for the NE40E-X8. In addition, each DC power output provided by one AC PEM is connected to one area. In this way, if one AC power input fails, the device still runs normally because of the power supply redundancy. The solution is also confirmed by Huawei R&D personnel.
Root Cause
The NE40E-X8 uses the technology of switched-mode power supply. The backplane has two areas, each of which has two power inputs, implementing backup. See Figure 1.

Figure 1 Power supply of the NE40E-X8

Generally, the NE40E-X8 has four AC power inputs, as shown in Figure 2.

Figure 2 AC power inputs of the NE40E-X8

Four DC outputs of the AC PDB are connected to the PEM to supply power to the left and right areas of the NE40E-X8.See Figure 3.

Figure 3 Connection between the AC PDB and the PEM on the NE40E-X8

Although the NE40E-X8 can work normally even when two AC power inputs are converted into two DC power inputs, there is no backup power supply in the left and right areas. Once one of the AC power supplies is faulty, no power supply is available in the corresponding area, causing services to be interrupted.
Considering that only two AC power supplies are available in the customer’s equipment room, it is recommended to draw two DC power supplies in parallel from one AC PEM of the PDB, and connect them to PEMs of both left and right areas of the NE40-X8 to implement power redundancy.