AC Supply

NoseyMike2010

Whay can't two AC power supplys work together providing redundancy. I mean when 1 supply is on and fails the other takes over. (I hope I am making sense here!!!)

Usually people prefer to use DC power supplies. Why? How are the 2 DC power supplies set up to provide this redundancy???

2011

What is the application?

NoseyMike2010

Lets say for PLC devices. I am not sure if its possible but that was why I raised the questions earlier.

DublinDilbert

With DC power supplies you can just diode OR the outputs together and either supply can drive the load. If one goes down the other kicks in. It's alot harder to do with AC waveforms...

NoseyMike2010

DublinDilbert,

Any chance you could draw it out on paint to explain what your trying to say. Thanks a million in advance.

Philistine

UPS (battery back-up) is fairly common for this application.

NoseyMike2010

Can anyone draw a rough circuit on paint and post it up here to explain ................ Sorry I am really lost and a good example will help. Thanks a million in advance?

DublinDilbert

NoseyMike2010 wrote: »

DublinDilbert,

Any chance you could draw it out on paint to explain what your trying to say. Thanks a million in advance.

On the phone so can't draw at the minute.

If you take two diodes, connect each anode to the + of the power supplies. Now connect the two cathodes together to supply the load. This allows either supply to deliver power to the load. A smoothing cap after this circuit wouldn't do any harm...

Philistine

Example circuit of a Siemens UPS module & battery unit.

See here for more detailed info:
http://www.automation.siemens.com/mcms/power-supply-sitop/en/24vdc/dc-ups/battery/Pages/default.aspx

For true PLC redundancy see here:
http://www.sea.siemens.com/us/Products/Automation/Programmable-Controllers/Redundant_PLC/Pages/Redundant_PLC_-_S7-400H.aspx

ShamFeen

NoseyMike, such a wide range of diverse questions. Thanks for the entertainment!!

mazthespark

the reason for using dc as a back up instead of ac is that You can store dc in batteries and convert back to ac via an inverter and i dont think its so easy to store ac power or even possible

firemansam1

ShamFeen wrote: »

NoseyMike, such a wide range of diverse questions. Thanks for the entertainment!!

:D:D:D:D:D:D::D:rolleyes::rolleyes::rolleyes::rolleyes::rolleyes::rolleyes::rolleyes:

Unreal

NoseyMike2010

Please see my attached ..... Can some body telly me if its set up correctly. What wave form should I expect at point B?


Is graph A even right??

DublinDilbert

The graph should be a flat line as they are dc supplies.

If you connect the cathodes of both diodes together to supply the positive side of the load.

ted1

what do you want it for? As stated above a uppups should serve your needs

NoseyMike2010

I am trying to learn the hardware element of setting up PLC's etc. i am trying to learn this on my own. Not sure how good/stupid my questions look!! Sorry if they are crap !!!!!!!!!!



This is a 24VDC Power supply isn't it?? http://www.kollewin.com/EX/09-15-20/xl480.jpg

Can anyone draw me a circuit to demonstrate it hooked up and show me it with redundancy? Cheers to all who help.

NoseyMike2010

I have a few more questions hopefully someone can help with

I am looking at the date sheet for the Allen Bradley Power supply
http://literature.rockwellautomation.com/idc/groups/literature/documents/ap/1606-ap018_-en-e.pdf

1) What does the following statements mean:

• MTBF 519.000h acc. to Siemensnorm SN29500

(24V/20A, 230V, Tamb = 40°C)

• Startup delay typ. 0.55s

Rise time appr. 20...80ms, depending on load

• Ambient temperature range
  Operation: 0°C...+70°C (>60°C: Derating)

2. What do the attached graphs explain??




PS .... Sorry to those who think my posts are amusing or stupid!!!!!!!!!!!!!

delly

ShamFeen and firemansam1, you input is no longer needed on this thread, please don't post again. firemansam1 this is your second warning in recent days.

Philistine

NoseyMike2010 wrote: »

This is a 24VDC Power supply isn't it?? http://www.kollewin.com/EX/09-15-20/xl480.jpg

Can anyone draw me a circuit to demonstrate it hooked up and show me it with redundancy? Cheers to all who help.

The power supply unit (PSU) in the link is 48vdc not 24vdc.

Circuit diagram attached for redundancy. Basically, you use two PSU's. One supplied from the usual source (MCC for example) and the second supplied from a UPS. You common the positives (+24vdc) together and you common the negatives (0vdc) together at terminals. Then you supply whatever it is you want from here. If the MCC goes down the UPS keeps power to one PSU.

brightspark

You can find a detailed explanation of MTBF here

http://www.batterypoweronline.com/images/PDFs_articles_whitepaper_appros/RockwellAutomation.pdf

The graphs show at what amperage the power supply is most efficient (between 10 and 22 Amps) you should size the power supply to the expected load (too big a power supply will waste power as well as outputing a slightly higher voltage, too small and it won't work at all)

Startup delay is exactly that.. how long the power supply takes to switch on.

The temp range is the temperature of the where the power supply is located, cabinets can get very hot or even cold depending on where thery are installed, operating the power supply outside of the designed range will result in less effeciency or even shorten its life.