IBM 4331 Mainframe 3 phase converter

Guy Sotomayor Jr ggs at
Thu May 4 11:10:55 CDT 2017

> On May 4, 2017, at 8:59 AM, Jon Elson <elson at> wrote:
> On 05/04/2017 10:36 AM, Guy Sotomayor Jr via cctalk wrote:
>> OK, that’s not helping.  Here’s what I have (from IBM site planning docs GC22-7064-10 and GC22-7069-2):
>> 3340-A2 DASD: 2.2 kVA 3-phase
>> 3340-B2 DASD: 1.7 kVA 3-phase (powered from 3340-A2)
>> 3803 Tape Control unit: 1.8 kVA 3-phase
>> 3420 Tape drive: 2.9 kVA 3-phase (powered from 3803) (x2)
>> 2821 control unit: 1.4 kVA 3-phase
>> 1403N1 Printer: 1.5 kVA 3-phase (powered from 2821)
>> 2540 card reader/punch: 1.2 kVA 3-phase (powered from 2821)
>> So I have 3 potential power feeds:
>> DASD: 3.9 kVA
>> Tape: 10.5 kVA
>> I/O: 4.1 kVA
>> For a total of 18.5 kVA
>> So the several $1000 question is how do the kVA’s map into 208v 3-phase amps?
> 18.5 KVA /208 = 88.94
> 88.94 / 1.732 = 51 A
> Since this is given as KVA, it should include the power factor.
>>   Depending upon how that works out I need to figure out if 2/3 converters make sense or just one big one.
>> My simple minded conversion is to take the 18.5kVA, multiply by 1000 and divide by 208.  That gives me just shy of 90A.  Do I then divide by 3 to get A/phase?  If so, then it’s 30A per phase which seems reasonable.  But I don’t know if that’s the correct formulation.
> It isn't.  See above.  A lot of this is circulating current, so the real power draw from the mains will be less.  Still, most likely over 10 real-power KW from your 240 V single-phase mains.


So if I want to run it off of one converter, that needs to be able to supply 51A.  If I split it, then I would end up with:
Tape: 30A
I/O: 12A

So at this point it comes down to cost.  If I can find one that can supply 60A that’s reasonable that would work.  Otherwise I’d likely get either 2 30A converters or 1 30A and 2 15A (if they come in those sizes).  ;-)  I’ll just have to figure out what makes the most sense cost wise.


TTFN - Guy

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