Muhendis Posted March 12, 2023 Share Posted March 12, 2023 11 hours ago, SomchaiDIY said: i think same you because changeover motor inside is 220v and using only one phase and neutral for single phase use best link all phase together because not sure which line inside circuit use for 220v control Good thinking and all worked out well. However. The reasoning is incomplete. In a 3 phase system the ATS needs to detect if any one phase is down. So the internals of the switch will be such that all inputs need to have power and if any one phase is lost the relay will be de-energised. 1 Link to comment Share on other sites More sharing options...
SomchaiDIY Posted March 16, 2023 Share Posted March 16, 2023 On 3/13/2023 at 5:55 AM, Muhendis said: Good thinking and all worked out well. However. The reasoning is incomplete. In a 3 phase system the ATS needs to detect if any one phase is down. So the internals of the switch will be such that all inputs need to have power and if any one phase is lost the relay will be de-energised. in many cheap cost chinese transfer switch only the one phase line is used for control this often line 1 or line a the switch do not care if other phases are missing at supply this is not best idea but is how many cheap 3 phase transfer switch work this only problem if all 3 phase required for some machine or system 1 1 Link to comment Share on other sites More sharing options...
Muhendis Posted March 16, 2023 Share Posted March 16, 2023 4 hours ago, SomchaiDIY said: in many cheap cost chinese transfer switch only the one phase line is used for control this often line 1 or line a the switch do not care if other phases are missing at supply this is not best idea but is how many cheap 3 phase transfer switch work this only problem if all 3 phase required for some machine or system That is scary. How many of these deadly things have you come across. "this only problem if all 3 phase required for some machine or system" In my world that's the whole purpose of 3Φ. Smaller motors etc. Link to comment Share on other sites More sharing options...
SomchaiDIY Posted March 17, 2023 Share Posted March 17, 2023 18 hours ago, Muhendis said: That is scary. How many of these deadly things have you come across. "this only problem if all 3 phase required for some machine or system" In my world that's the whole purpose of 3Φ. Smaller motors etc. these cheap transfer switch have only the 2 position missing phase transfer switch have 3 position center off center off used when phase missing or supply fault critical backup supply require good supply check before transfer possible here is photo for 3 position with center off and faulty power detect if phase loss in our factory area no big problem for us all cnc shutdown with no volt detect other motor trip from thermal overload in control panel this happen many times in the year here is video of cheap 4 pole 2 position switch using only the 1 phase 1 1 Link to comment Share on other sites More sharing options...
Muhendis Posted March 17, 2023 Share Posted March 17, 2023 16 hours ago, SomchaiDIY said: these cheap transfer switch have only the 2 position missing phase transfer switch have 3 position center off center off used when phase missing or supply fault critical backup supply require good supply check before transfer possible here is photo for 3 position with center off and faulty power detect if phase loss in our factory area no big problem for us all cnc shutdown with no volt detect other motor trip from thermal overload in control panel this happen many times in the year here is video of cheap 4 pole 2 position switch using only the 1 phase Thanks for the reminder. 1 Link to comment Share on other sites More sharing options...
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