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In Thailand we usually use 3 phases (L1, L2, L3) + Neutral (N) + Ground (PE) with 220V.

A machine imported from Taiwan has four connectors: L1, L2, L3 and Ground (connected to the housing).

It uses this mainly for motor controllers (SDB-075A2), some relays and motors.

The technician setting up the machine says there must be 220V between L1 and L2, 220V between L2 and L3 and 220V between L3 and L1.

I was under the impression that if we wire our incoming Y configuration in a delta way (leave out the N), there would be around 380V between the phases.

How would it have to be connected to have 220V between the inputs?

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Well, this is a difficult area.

It is possible the engineer was mistaken and that it needs a 220V 3phase system without neutral to make 380V between phases.

It is also possible it's a 120V machine without neutral, making the phase to phase voltage quite close (but only just not) to 220V -- About 205V.

I would expect it's more likely the first one, but since my vision isn't good enough to read labels all the way from Europe, promises will not be made.

EDIT:

Looking at the motor controller you linked it's even more likely the first option, but still no guarantee can be made, since you say it's a total machine in which that controller lives, between the controller and machine input all kinds of stuff can be happening. But it is, indeed, unlikely.

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  • \$\begingroup\$ I found this manual for a slightly different controller, and it requires a "single-phase 220V power source" for the control panel. The wiring diagram connects this to L1 and L2 of the three-phase supply, so apparently this is actually a supply with 220V across phases. \$\endgroup\$
    – AndreKR
    Aug 6 '15 at 10:14
  • \$\begingroup\$ @AndreKR Sad fact is, that where there are "a couple" of options for single phase, for 2 and 3 phase it gets exponentially bad. So, you have your answer then. \$\endgroup\$
    – Asmyldof
    Aug 6 '15 at 11:24
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    \$\begingroup\$ I wouldn't be confident either way. The brochure implies 200-230V phase to phase. Taiwan uses 110V phase to neutral which is 190V phase to phase. The 200-230 figure to me implies it's a badly described 220V phase to neutral (380 odd phase to phase) but frankly I wouldn't dare connect it up without contacting the manufacturer for clarification, in case the wrong guess results in it turning into an expensive smoke generator. \$\endgroup\$
    – Ian Bland
    Dec 4 '16 at 18:21
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To convert your 380/220 Y supply to 220 delta or 220/127 Y, you need a transformer. The motor controller brochure seems to indicate that it can operate on 220 single-phase, but the manual indicates that a different model is required for single-phase. If there are other motors on the machine, they may also require three-phase power. It does not seem likely that the machine can be converted to use 220 volts single-phase.

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  • \$\begingroup\$ So 220/127 Y is a thing? We do have a transformer (interestingly enough it was on stock in a local transformer shop) but I wondered why they would build the machine that way in the first place. \$\endgroup\$
    – AndreKR
    Aug 6 '15 at 18:01
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    \$\begingroup\$ I don't think that 220/127 Y or 240/139 Y are systems used with anything but ground connected to the neutral. In the USA, there are some small industrial and commercial buildings that have 240 delta systems that have a grounded neutral in the center of one of the phases to provide 240/120 single phase. The standard for USA industrial use is 480 V, 3-phase. It is easy to build 3-phase dual voltage motors for 240/480 V. \$\endgroup\$ Aug 6 '15 at 19:00
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    \$\begingroup\$ I agree with @CharlesCowie, you can't get there from here. If your 3-phase service is 220V hot to neutral, then it's 380V hot-to-hot. That is not what a 240V 3-phase motor wants to see. If your servo-drive will accept 220V single-phase, you may want to connect it hot-neutral. \$\endgroup\$ Dec 13 '16 at 23:47
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You are absolutely correct, leaving out the NEUTRAL, you will have 380 V across L1 to L2 and L2 to L3. But to have 220 V the NEUTRAL is a must between each phase and the neutral will give you 220 V. This system is called Three-phase 220 V. Unlike the 220 V three phase, you don't need a neutral, with a good GROUND will give you 220 V.

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    \$\begingroup\$ You need to give some reference for "This system is called Three-phase 220 V" and say what country/ies this terminology is used in. I don't think it would be used anywhere in Europe without specifying that it is phase to neutral. Three-phase 220 V is not enough to be sure. \$\endgroup\$
    – Transistor
    Aug 11 '17 at 20:03

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