Meggitt RPS6U power supply

Rating reduction and heat dissipation: 50 ° C is an important boundary line

The power capability of RPS6U is closely related to the cooling method. Under natural convection cooling, the AC version's+5 VDC output is rated at 2.5%/° C from 50 ° C to 70 ° C, and the ± 12 VDC output is rated at 4%/° C from 55 ° C to 70 ° C; The+5 VDC versions of 24 VDC and 110 VDC are rated 2%/° C off from 50 ° C to 70 ° C, and ± 12 VDC is rated 3%/° C off from 60 ° C to 70 ° C. If forced air cooling is used, the AC version does not require derating; The DC version of+5 VDC still requires a 2.5%/° C derating at 60-70 ° C, while ± 12 VDC does not require derating.

This means that in enclosed cabinets or high-temperature computer rooms during summer, just looking at "330 W" is not enough. If the rack is fully equipped and the ambient temperature exceeds 50 ° C, priority should be given to evaluating forced air cooling or adopting a dual power non redundant configuration. For the scenario of replacing the old power supply, it should also be noted that the early RPS6U before 2016 was rated at 300 W, with outputs of+5 VDC up to 35 A,+12 VDC up to 6 A, and -12 VDC up to 2 A; the later 330 W version, although compatible in appearance and installation, had different power budgets. Replacing an old version with a new version usually has a larger power margin, but if the old version is replaced with a new version in reverse, the load must be recalculated to avoid power failure or module reset under high temperatures.

The rear panel determines input protection and external wiring

The front panel of RPS6U is only responsible for the power module itself, and the actual external input wiring, switches, fuses, and redundant switching are often completed by the rear panel of the rack. The AC input rear panel usually includes fuses, filters, and mains switches. Some versions come with IEC C14 sockets, while others use screw terminals; The dual AC input version can achieve automatic switching or separate feeding of two independent AC power sources. The DC input rear panel usually does not include DC input protection, and suitable rated circuit breakers or equivalent protections must be configured in the external distribution circuit. The DC rear panel has different forms such as single input, dual independent input, M.A.L.T. grounding terminal, and protective diode; The dual independent DC input version is connected to the same node on the backplane through a protective diode. When one DC power supply fails, the other can continue to maintain rack operation.

When replacing spare parts, it is not enough to only look at the PNR of RPS6U. The PNR of the rear panel is related to the rack input mode, slot width, and whether it supports ASPS auxiliary sensor power supply. Some rear panels are 2 slots wide/8 HP, while others are 4 slots wide/16 HP; AC rear panels come with fuses, while DC rear panels do not. If the on-site power supply is DC, when replacing the power supply, it is also necessary to confirm that the rated value of the external circuit breaker matches the maximum input current of the new power supply. For the two generations of VM600Mk2 and VM600 products, the VM600Mk2 version after 2021 is basically the same as the latest VM600 version in terms of functionality, with the main difference being the brand logo and front panel coating: the Mk2 version has a bare aluminum front panel, while the VM600 version has a painted front panel. The increment of hardware version number "h" usually only represents minor modifications that do not affect interchangeability, but changes to larger version "H" may affect interchangeability, and the complete PNR should be checked when ordering.

LED status and fault diagnosis

The RPS6U front panel provides four status LEDs. The top "IN" is green, indicating that the external mains power supply exists and is within the normal range; The three yellow LEDs below correspond to normal outputs of+5 VDC,+12 VDC, and -12 VDC, respectively. The on-site inspection can be carried out in the following order.

If "IN" does not light up, check the input switch, fuse, external circuit breaker, and incoming voltage on the rear panel first. The AC version needs to confirm that the input voltage falls within the range of 90-132 VAC or 180-264 VAC; The DC version needs to confirm that the 24 VDC version is within the range of 18-32 VDC and the 110 VDC version is within the range of 80-145 VDC. If "IN" is normal but one of the yellow lights is not on, it indicates that the output of the circuit is abnormal or there is a short circuit/overload on the load side. The short-circuit and overload protection of RPS6U is automatic recovery type, which can be restored after eliminating load faults; Overvoltage protection is an automatic locking type that usually requires a power outage and restart to reset. Therefore, it is necessary to first check if there are any abnormalities on the backplane or module side before powering on again.

In a redundant configuration, when one power supply fails, the other can still maintain rack operation, and only one power supply's LED abnormality may be seen on site, but the system has not shut down. At this point, processing should not be delayed due to the system still running. The input, output, and backplane connections of the faulty power supply should be confirmed as soon as possible, and replaced according to the shutdown maintenance procedure. In a non redundant dual power configuration, if one power supply fails, the remaining power supplies may only be able to bear part of the load, and the system may reset or modules may lose power. Therefore, more attention should be paid to load distribution and high-temperature derating.