Problem with UPS transfer switch based on triac

Hi !

I have designed a tranfer switch based on triac. It is to be operated between the output of a modified sinewave inverter and the load.It triggers whether the line is missing or not.The switching time OFF--ON (blackout to emergency ) is about 10ms and the ON--OFF (emergency to AC line OK) is about 10us.I want to connect in parallel the AC line and the output of the transfer switch to feed the load,and my question is :Could the output stage of the inverter be damaged by doing this as during the 10us ON--OFF time it happens that AC line and Inverter output are present at the same time( the transfer switch can trigger only 10us after AC line presence)?What could be done to avoid this??
(maybe adding another transfer switch from AC line to load with a larger delay time say 30 us ??)

thank you in advance


regards

maXer

Re: ups transfer switch!

maxer said:

Hi !

I have designed a tranfer switch based on triac. It is to be operated between the output of a modified sinewave inverter and the load.It triggers whether the line is missing or not.The switching time OFF--ON (blackout to emergency ) is about 10ms and the ON--OFF (emergency to AC line OK) is about 10us.I want to connect in parallel the AC line and the output of the transfer switch to feed the load,and my question is :Could the output stage of the inverter be damaged by doing this as during the 10us ON--OFF time it happens that AC line and Inverter output are present at the same time( the transfer switch can trigger only 10us after AC line presence)?What could be done to avoid this??
(maybe adding another transfer switch from AC line to load with a larger delay time say 30 us ??)

thank you in advance


regards

maXer

Click to expand...

First moment in blackout situation is to cut connection to main-feed, before activating your converter if you not want feeding whole city from your UPS.

blackout is not same as cutted main-wire and open end, in most case stand for shorted situation from unpowered heavy load from in and outside house - so if you put on converter here, you handle almost shorted output.

Syncronization on your internal 50 Hz generator is importent so your modified sinus continue voltage envelope replace for missing mains. transformer and motors handly badly if you try with 90 or 180 degre phase shifted voltage and possible give high current or voltage surge in switch moment.

you must make switch so reactive inductive current from load can still running in switch moment between main and converter mode - or you make very high voltage spikes etc.. small switchtime in couple of us can handle with capacitance, but long time in tenth of ms must handle in other way. Current from fluorescent tube, motors and trafos can lagging around 45 degree after voltage and you need handle same amount of reaktive power as real power here.

you need also syncronize 50 Hz oscillator to main in situation as main come back and only close mains switch in situation converter have same voltage in envelope as mains (+/- few volt) and let converter going high impedances quickly if converter not can follow main voltage shape without current surge (different shape between real sinus and modify sinus aka square wave) if you cut converter before switch to mains (still in rigth phase angle), you also need handle reactive power as above disscussed...


Remember:

You have no time to fix syncronize problem etc. after blackout situation , so fix this before and stay alert.

You have good time syncronize after mains comes back (couple of seconds), so don't hurry and fix switch moment back to main smoth and safty.

---



My 2 cents

Re: ups transfer switch!

Dear, hope this finds you in the best of your health.

I am facing a very odd kind of problem with ups transfer switching. I recently bought 30 ups devices all 1300 watts, Line interactive, with 2000 watt surge protection. Transfer time is <10ms. The reason i installed these ups's was to avoid data center restarting. now when the main power is cut some times it restarts and some time it switches normal. more frequently it restarts the equipment when the main power comes back. can this be due to diesel power generators?

can u advice please.

Re: ups transfer switch!

scorpy77 said:

Dear, hope this finds you in the best of your health.

I am facing a very odd kind of problem with ups transfer switching. I recently bought 30 ups devices all 1300 watts, Line interactive, with 2000 watt surge protection. Transfer time is <10ms. The reason i installed these ups's was to avoid data center restarting. now when the main power is cut some times it restarts and some time it switches normal. more frequently it restarts the equipment when the main power comes back. can this be due to diesel power generators?

can u advice please.

Click to expand...

dear scorpy77 ,
i think problem is with ups , it switch over time varies some time 10ms and some time more then 10ms and ur computer will always be restart if chageover took place grater then 10ms time.

---------- Post added at 07:37 ---------- Previous post was at 07:24 ----------

maxer said:

Hi !

I have designed a tranfer switch based on triac. It is to be operated between the output of a modified sinewave inverter and the load.It triggers whether the line is missing or not.The switching time OFF--ON (blackout to emergency ) is about 10ms and the ON--OFF (emergency to AC line OK) is about 10us.I want to connect in parallel the AC line and the output of the transfer switch to feed the load,and my question is :Could the output stage of the inverter be damaged by doing this as during the 10us ON--OFF time it happens that AC line and Inverter output are present at the same time( the transfer switch can trigger only 10us after AC line presence)?What could be done to avoid this??
(maybe adding another transfer switch from AC line to load with a larger delay time say 30 us ??)

thank you in advance


regards

maXer

Click to expand...

Hi,
I also designed tric based transfer switch with the combination of a relay and its change over timing was good & below 10ms but it has got serious problems with modified sine wave of ups . When ups out passes through tric then it power reduces in such a way that it hardly becomes able to run a 25watt energy saver light. i am not exactly sure what is the reason but it is sure that we can not use tric to pass modified sine wave output properly.