How many phases? And another Lucien grumble: 'Amps Per Phase' Discussion ThreadHow many phases? And another Lucien grumble: 'Amps Per Phase' Electrical Advice
When I joined this forum a decade or so back, there was a discussion going on about a welder that was connected with a 3-core cable to L1, L2 and earth of a 3-phase supply, operating on the 400V present between L1 and L2. The advantage of choosing 400V is the reduced current requirement. My own portable stick welder has this option too with a voltage selector on the back. It will run on 16A if 400V is available, but 32A is needed if you switch it down to 230V.
According to the particiapnts in that discussion, the use of L1 and L2 made it a ‘2-phase welder’ because it was 'connected to two phases.'
'No,' I said:, 'it's single-phase' and was quickly admonished that I didn't know what I was talking about, and told to go and look up some definitions (that was the usual reaction back then to pretty much any newcomer.) I tried to make the distinction between various configurations:
a) A single phase device operating at the line-line voltage of a polyphase supply like this welder, using two line wires but no connection to the neutral.
b) A device that specifically needs two lines out of a 3-phase supply and its neutral.
c) A genuine two-phase supply and load that has two separate coils operating out-of-phase, historically usually 90 degrees apart, which would require two lines and a neutral, or two separate pairs of line and neutral.
Tony Smith knew I knew my onions here and didn't argue with me, but we moved on swiftly anyway and the point got brushed aside. It has resurfaced in a number of guises since, including a recent conversation, and I think I've finally realised where the misunderstanding comes from.
We often talk about the line conductors as phases and most people use 'phase' and 'line' interchangeably in many 3-phase contexts. E.g.
'Which phase is that lighting circuit on?'
'Put the immersion on a different phase to the lobby heater!'
‘He didn’t say which phase is dead but I think it’s L2.’
These sound completely natural and make sense when we consider...
Read more
How many phases? And another Lucien grumble: 'Amps Per Phase' for the original thread on Electricians Forums
When I joined this forum a decade or so back, there was a discussion going on about a welder that was connected with a 3-core cable to L1, L2 and earth of a 3-phase supply, operating on the 400V present between L1 and L2. The advantage of choosing 400V is the reduced current requirement. My own portable stick welder has this option too with a voltage selector on the back. It will run on 16A if 400V is available, but 32A is needed if you switch it down to 230V.
According to the particiapnts in that discussion, the use of L1 and L2 made it a ‘2-phase welder’ because it was 'connected to two phases.'
'No,' I said:, 'it's single-phase' and was quickly admonished that I didn't know what I was talking about, and told to go and look up some definitions (that was the usual reaction back then to pretty much any newcomer.) I tried to make the distinction between various configurations:
a) A single phase device operating at the line-line voltage of a polyphase supply like this welder, using two line wires but no connection to the neutral.
b) A device that specifically needs two lines out of a 3-phase supply and its neutral.
c) A genuine two-phase supply and load that has two separate coils operating out-of-phase, historically usually 90 degrees apart, which would require two lines and a neutral, or two separate pairs of line and neutral.
Tony Smith knew I knew my onions here and didn't argue with me, but we moved on swiftly anyway and the point got brushed aside. It has resurfaced in a number of guises since, including a recent conversation, and I think I've finally realised where the misunderstanding comes from.
We often talk about the line conductors as phases and most people use 'phase' and 'line' interchangeably in many 3-phase contexts. E.g.
'Which phase is that lighting circuit on?'
'Put the immersion on a different phase to the lobby heater!'
‘He didn’t say which phase is dead but I think it’s L2.’
These sound completely natural and make sense when we consider...
Read more
How many phases? And another Lucien grumble: 'Amps Per Phase' for the original thread on Electricians Forums
