2 Live + ground is two phase. A three phase supplies doesn't need a ground, but usually one is provided to allow single phase equipment to be used.
Power is generated by three phase alternators and these expect the load on each phase to be identical. So in most areas of buildings where high power is used (e.g. a large machine room or server centre) there will be outlets connected to each of the three phases and attempts made to balance the load across the phases. Certainly in the UK using the power in an unbalanced way may result in financial penalties. Typically three phase equipment performs the balancing internally so are "desirable" from the suppliers point of view. Even when we ran 4381's we still had a mix of three phase and single phase, but of course we are on 22volts. I don't think there is any three phase stuff left in our machine room any more. Dave Wade G4UGM Illegitimi Non Carborundum -----Original Message----- From: The IBM z/VM Operating System [mailto:[email protected]] On Behalf Of John Harris Sent: 04 May 2009 17:05 To: [email protected] Subject: Re: z890 power: 3 phase vs 1 phase? The main difference between single phase and 3-phase (basically a ground and 2 live circuits) is the resultant voltage. Single-phase = 110v US and 220v UK 3-Phase = 220v US and 385v UK All heavy duty applicances in the US (A/Cs, Washer/Dryers, Electrical cooktops etc) use 220v,(3phase). By supporting 3-phase, appliances can run in a multi-tude countries and the manufacturer only has to worry about the frequency i.e. 50/60hz between the regions. I had one pulled into my garage for my 220v tools. My 2-cents worth John Harris IBM ------ Original Message ------ Received: 11:37 AM EDT, 05/04/2009 From: Dave Jones <[email protected]> To: [email protected] Subject: Re: z890 power: 3 phase vs 1 phase? That's right...the z boxes basically have an a/c system built into them. The a/c units here at the house (living here in Houston, we know a thing or two about a/c....) both run on three phase power. Alan Altmark wrote: > On Monday, 05/04/2009 at 08:57 EDT, Dave Jones <[email protected]> > wrote: >> Well, the z boxes all have motors to drive the fans, but I do not >> understand why they would need 3 phase power..... > > Don't forget the coolant compressors. > > Alan Altmark > z/VM Development > IBM Endicott -- Dave Jones V/Soft www.vsoft-software.com Houston, TX 281.578.7544
