How to connect two idustrial SMPS'es with a "system bus" in parallel.  - Page 1
Forum section: electronics / general

author: Fflint
author_rank: Frequent Contributor
timestamp: December 03, 2021, 09:41:05 pm
content: So after successfully repairing one I now have two of those 1900W 48V Ascom Italian SMPS'es (here is manufacturer's infohttp://web.tiscali.it/gnnsites/rdz_SMPS48V1900.htm)As far as I can tell they are designed to able to be connected together for up to 9 of them. They were initially designed for powering GSM base stations. They have two RJ-11 sockets labelled "system bus". The manufacturer specs just says they come with a "digital or analog system bus". I hope the two I have both have the same system bus type.So now comes the difficulty. There is zero information on the Internet about them. The manufacturer company doesn't appear to exist anymore (there is a company called Ascom, but they don't do power systems. There is a press note from 2002 that they sold their power division to a company in Thailand. As far as I can tell that company hasn't done anything with their acquisition. The original domain ascom power.it has not been renewed). The original email bounces and I have no manual.I'm not sure if I should connect those rj-11 ports and in which configuration. Having just repaired one I'm reluctant to connect them randomly.I have no idea what kind of bus is most likely to be used in a GSM station SMPS. Is it likely to be Can, or something else?If anyone familiar with such SMPS'es could tell me few likely candidates for what kind that "system bus" might be I could start probing with an oscilloscope trying to narrow down to the right one.In addition to the rj-11 system bus the power supplies are equipped with multi-turn potentiometers to set the voltage (33V to 55V) and a current limit. Also they have two ports on the front panel. One for monitoring the voltage, and one for monitoring the current draw.

author: Gregg
author_rank: Super Contributor
timestamp: December 03, 2021, 11:27:22 pm
content: Most of the hot swappable telco SPMS modules won’t parallel without a control module; many won’t work at all without the control module unless the remote control function is bypassed internally. Reverse engineering them is very difficult because they are so tightly packed together.Many of them communicate by old school RS232 or RS485 largely because most of things telco are firmly planted in the past.

author: Fflint
author_rank: Frequent Contributor
timestamp: December 04, 2021, 12:23:52 am
content: Thanks.I don't think those can be called hot swappable modules.Those power supplies work fine on their own (standalone). Also based on the translated text below I believe they can be paralleled without any extra equipment (perhaps one need to preconfigure them for that?)This is a translation of the original Italian description :"The SMPS 48V - 1900 W rectifier is expressly designed for powering telecommunication equipment, it is often used in systems that supply energy in medium / low power GSM base sites.This rectifier can be used either individually or connected in parallel with other modules of the same type.The SMPS 48V - 1900 W rectifier has automatic control of the output power, in fact the supply of 1900W is guaranteed for the entire specified voltage calibration range.The modules are equipped with a protection circuit against overheating and cooling is by natural air convection.All connectors, switches and calibration screws necessary for the rectifier to operate are placed on the front panel to allow for prompt adjustment. The compact dimensions and the high quality of the components make the SMPS 48V-1900 W rectifier an extremely reliable and easy to use module."endIn addition to two RJ-11 ports labelled "system bus" there is an edge connector on the pcb that is hidden behind a panel. I suspect this edge connector is used either for initial programming or for an optional control module.I have no intention of modyfying them etc, but if there is a simple way to parallel them just by hooking up those RJ-11 ports in some way I would like to do it.The fact there are two RJ-11 ports labelled with the "system bus" may mean one of few things to me:- each is different in some way, possibly one is analog one digital? I doubt that because the manufacturer page said analog/digital system bus was a choice. My understanding of it is that there are some devices with the analog and some with digital system bus rather than both being present in one device.- It is meant to "daisy chain" devices. One is an input, the other an output? That would be ideal.With regard to the system bus being RS-232 or Rs-485. RJ-11 provides 4 connections. That would fit a double twisted pair signalling like RS-485 well. Is CAN used with power supplies like this too?