raithrovers1
Industrial
We have a PWM UPS that replaced an old Ferro UPS. The site decided to re-use the bypass tarnsformer from the original UPS. This transformer is a ferroresonant constant voltage transformer.
When commissioning the new UPS it was found that the UPS seems to work as designed. The problem only arises when a static transfer to the bypass supply is initiated. As soon as the command is given the inverter grunts loudly as if it is feeding a short circuit. The UPS does not transfer to bypass and remains on Inverter static switch. If the inverter OFF command is given to the UPS then a transfer to static bypass happens without any problems.
Therefore my question is: does anyone know of a reason that a PWM inverter cannot be fed by a Ferro bypass supply? It seems that the only problem is when both static switches are on for the very short overlap period. This seems to cause a high amount of circulating current.
Thanks as always for any help.
P.S. I will not be at this site anytime soon to perform any further investigations at this time.
UPS Service Manager
When commissioning the new UPS it was found that the UPS seems to work as designed. The problem only arises when a static transfer to the bypass supply is initiated. As soon as the command is given the inverter grunts loudly as if it is feeding a short circuit. The UPS does not transfer to bypass and remains on Inverter static switch. If the inverter OFF command is given to the UPS then a transfer to static bypass happens without any problems.
Therefore my question is: does anyone know of a reason that a PWM inverter cannot be fed by a Ferro bypass supply? It seems that the only problem is when both static switches are on for the very short overlap period. This seems to cause a high amount of circulating current.
Thanks as always for any help.
P.S. I will not be at this site anytime soon to perform any further investigations at this time.
UPS Service Manager
