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Power Rail Booster

Created by: svaneenoo at: 7/10/2006 8:26 PM (2 Replies)

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7/10/2006 8:26 PM	Rate (0)
svaneenoo Regular Member Joined: 7/10/2006 Last visit: 1/25/2023 Posts: 2 Rating: (0)	I'm commisioning a plant with 2 power feed system with integrated profibus connection for concrete transport cars. For the profibus connection we're using a power rail booster from siemens. There are 2 power rail boosters in the main cabinet for putting power on the 2 power feed systems and 1 power rail booster in each transport car. Sometimes there is a very short communication drop between the power rail boosters. Does somebody know a method to get more information out of the power rail booster? I looks like the fault occures when there is one of the other motors starting in the main cabinet but not all of them and not always. ( direct start motors ) Things i've check so far are : earth, power, lowest baudrate, insulation test on my motors, moved the datacable to the power feed system away futher from the power cables, replaced the datacable to the power feed system... Anyone more familar than me with the power rail booster ? Is there information about the signal between the power rail boosters ? I suppose it is a current signal ? Could it be possible that the power rail booster signal is influenced ? But how ? Any comment highly appreciated ! Best Regards, Stefaan PS : Documentation about the power feed system i'm using and configuration of the wires you'll find here - download documentation and then look on page 6. My configuration is the 2nd one from the right. PS : The Siemens salesman told me that there should be a distance of 20 cm between the power and the data in the power feed system? Does somebody know a manufactor who makes power feed systems with that specifications? Attachment beton.jpg (843 Downloads)

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7/11/2006 11:25 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Hi, Have you checked on both sides the Profibus Telegrams, on the moving part would be not that easy, but first start on the steady part. With a Busmonitor like Amprolyzer (needs a CP5611) you may check whats happening. [:o] I don't believe that the distance have to be 20 cm, thats for data signals, I have read several handbooks where they say 10cm. Because this is a power boostet signal there might be no influence off disturbance, only when the distance is very small. [:P] If you measuring the Profibus signals, and you have a every day backcoming disturbance of the signalthen you can find how long the signal is gone away. It is also possible to check in the PLC how long the signal was disturbed, with a Simatic S7 you can check how long the signal was gone by checking with OB86 the incoming and outgoing disturbance. It is also nice to know if there is a disturbance on one place (checking in the PLC where the lory is). You can also change some parameters of the Profibus, like the retry factor. It will be more likely a "mechanical" disturbance in the powerrail. Siemens can help you to measure the Profibus signals if you don't have the equipment to do that.
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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7/24/2006 5:50 PM	Rate (0)
The Mechanic Posts: 48 Rating: (4)	Hi Stefaan, Maybe I can help you with some information about the power rail booster (PRB). Usually when I am confronted with PRB communication problems there are two types of causes: 1.A mechanical cause. 2. Anelectrical cause (EMV). On 1: Sometimes the guidance rail has a mechanical flaw. As a result the guidance does not connect to it's rail properly. This leads to a communication dropout. If this is the cause thenthe problem should always occurwhen the transport car is atthe same position. On 2: Although the PRB signal is more robust than a standard Profibus signal, there is always the chance of EMV related problems. Usually the power rail does not only transmit signals, but also the 400 Volt for the drives. The short relative distance between powerdistribution and signals and the fact that they run in parallel increases this risk. I suggest trying to find out first whether the problem always happens in the same position or when a particular motor is started. Do you only use motorstarters or also Frequency Converters? I would also like to answer some of your questions: 1. Sometimes there is a very short communication drop between the power rail boosters. Does somebody know a method to get more information out of the power rail booster? Answer 1: The PRB does not have much diagnostic options other than the LED display. But you could try using a diagnostic repeater. 2. I looks like the fault occures when there is one of the other motors starting in the main cabinet but not all of them and not always. ( direct start motors ) Answer 2: So it seems to have some sort of EMV related cause. The problem with EMV is that it is very difficult to predict what will happen. You could try using a diagnostic repeater here to check your wiring., It might also be able to, up to a certain extent, detect EMV related problems. 3. Things i've check so far are : earth, power, lowest baudrate, insulation test on my motors, moved the datacable to the power feed system away futher from the power cables, replaced the datacable to the power feed system... Anyone more familar than me with the power rail booster ? Answer 3: It seems that you have done all the things I would have done also. Next thing I would try is to do some test runs in which you deliberately start or do not start the motors that are on the transport car. Let's see if we can find out which motor or motors are causing this problem. Don't forget to consult your power rail supplier. They might be able to help you out. also check the manuals and the internet for the specifications of the power rail. 4. Is there information about the signal between the power rail boosters ? I suppose it is a current signal ? Could it be possible that the power rail booster signal is influenced ? But how ? Answer 4: You could check the manual for that. Generally the power rail booster transforms the 5 Volt Profibus signal into a much more powerful and robust power rail signal. But this doesn't mean it's invulnerable to EMV. I hope this information will help you out. Please let me know if you''ve managed to solve it. We'd also like to know the cause of the problems. The Mechanic.
The Mechanic Posts: 48 Rating: (4)
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