[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

1154.0. "48V DC Power requirements" by MINNY::SCHUMACHER (More than cows & chocolate...) Fri Jun 24 1994 05:39

    A customer decided to run 4 DEChub900 on 48V DC exclusively. The
    application behind is a Power Distribution Control System with 
    high availablity requirements.
    
    For 220V AC devices we have a number of technical requirements
    in our data sheets (Max. Power, Voltage tolerances, max. Distortion,
    etc)
    
    What kind of requirements ( or environmental conditions) do we have
    for the 48V DC area?
    
    Many thanks if someone could shed some light on that
    
    /Peter
T.RTitleUserPersonal
Name		DateLines
1154.1Spec say's 40-54VDC, but 60VDC is OKDELNI::MACARTHURMon Jun 27 1994 14:0622
    Peter,
    
        The external 48V Input characteristics for a DEChub900 system are
    as follows:
     
    Min Voltage = 40 VDC
    Max Voltage = 54 VDC
    Maximum Input Ripple Voltage = 1.0 Vrms
    Max current (@40 VDC) = 4.6 Arms
    
    The specifications for the two DC-DC converters used in the H7890-MA
    allow an input voltage as high as 60 VDC. Even though the specification
    for the power supply only goes to 54 VDC, I'm sure that you can operate
    the supply up to 60 VDC without causing any problems (I'm the
    responsible engineer for the DEChub900 Power System).
    
    The environmental specification for the DEChub900 system operating from
    a 48 VDC input is no different than that of an AC powered DEChub900
    system (40 degrees C maximum ambient temperature). Hope this answers 
    your questions.
    
    Bob
1154.2more detail on 48v supportKALI::SOHATue Jun 28 1994 13:0346
    Peter,             
    
                        
    Here's a little more detail on 48V support for the DECHub900.
    
    The DEChub900 power system is designed to run off either AC line
    or 48v DC.  This is accomplished by a two stage power supply 
    design, as shown below.
    
                |----------------|
    AC Line --->| AC/DC-+--DC/DC |---> DC Outputs
                |       |        |--->
                |-------|--------|
                        |
                        ^
                       48 V
    
    The DC/DC section of the supply will accept either input (AC/DC output
    or ext 48V).  The method we chose to always use AC when it's available is
    to have the AC/DC output be at 50V and the ext 48V supply at a lower 
    voltage (say 48V).  Therefore, when both the ext 48V and AC are 
    operational, the system will use AC power.  
    
    A couple of observations:
    
    1.  An external conditioner will be required to ensure that the 
        external 48V remains below 50V.  Typical US 48V telco system
        vary from 40-60 volts.  Once the system detects loss of AC
        (ie, backup mode), this voltage can rise to 54 volts.
    
    2.  If a user wants to solely run off 48 V (that is, no AC presnt)  
        a external supply can be used that meets the specs of reply .1.
    
    
    The external conditioner is planned for FY95.  A detailed schedule
    has not been developed.
    
    Hope this helps,
    
    Mike S.