Siemens 417-H PLC problem

hi all,

need some opinion on the problem that i'm facing. i have a siemens 417-h (redundant) PLC that control our exhaust system at site. the problem is, we had a power trip at the PLC. however, on site all the exhaust are still running. but after the power to the PLC had been recovered, somehow it affected one unit of the exhaust and cause it to stop and restart back instantly. (fyi, we have 5 unit of the exhaust).

the exhaust system is using VSD control through the motor manager system that connect the the PLC through the CMAC system.

my question is, why during the power trip at the PLC, the exhaust all still running without interruption?

why only the exhaust affected during the PLC recover back? is the logic from the PLC that control the exhaust running unit and cause it to be interrupted? why only one unit then? (fyi, there is logic control for number required to run which will ON and OFF the exhaust depending on the demands.. however, this applies in normal condition only). never had this scenario before that the PLC power trip but the site power to the exhaust system still ON.

PLS help advise if you face this or have any idea why is this happening.

thanks a lot.

regards..
PCY

Hi everyone,

I am looking PLC for controlling water tidal-test tank for laboratory test purposes. Could someone please guide me which PLC should I use? Is Fatek (FBS24-MA, 32 I/O) one good? Basically, it will be using for water level control during loading and unloading of the goods in Marine industry or sea ports.
Information will be really helpful and cooperation will be really appreciated.
Thank you