risk of UPS feeding UPS
- Thread starter dozzer1
- Start date
- Status
bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
Possibly some interaction. This could occur due to the inductive characteristics of the inverter output of the larger (assuming 3-phase) system and the capacitive input of the 1 phase UPS. You could be creating a nice little tuned circuit between the 2 UPS systems with wildly oscillating voltage magnitudes. Check the voltage and current harmonics between the 2 UPS systems.
rick hart
Senior Member
- Location
- Dallas Texas
I have had problems with ferroresonant UPS feeding online rackmounted UPS- mysterious shutdowns. The UPS tech blamed Sun Microsystems equipment... not sure if that was legit.
dave_asdf
Member
- Location
- tampa florida
Rick,
was the rackmounted UPS causing the upstream UPS to shutdown? i am currently troubleshooting a problem where a 150 KVA double conversion UPS transferred to static bypass a couple times for "no reason". i installed a power quality meter on the only downstream transformer the UPS supplies and noticed rhythmic voltage fluctuations of about 1 - 2 volts (at 120 phase-n) every second or so on all phases. i'm not sure if that corresponds to the conditions you had seen but i'm trying to cover all my bases with this mystery.
Thanks, Dave.
was the rackmounted UPS causing the upstream UPS to shutdown? i am currently troubleshooting a problem where a 150 KVA double conversion UPS transferred to static bypass a couple times for "no reason". i installed a power quality meter on the only downstream transformer the UPS supplies and noticed rhythmic voltage fluctuations of about 1 - 2 volts (at 120 phase-n) every second or so on all phases. i'm not sure if that corresponds to the conditions you had seen but i'm trying to cover all my bases with this mystery.
Thanks, Dave.
catchtwentytwo
Senior Member
When faced with this type of situation, we put an isolation transformer on the input of the second UPS.
dave_asdf
Member
- Location
- tampa florida
the current configuration is 480v 3 phase UPS --> 75 KVA xfmr --> 120v 1 phase UPS. oh well, when i saw that i was hoping i might have the same problem, been scratching my head about this one for a while.
thanks
PS i also checked, that UPS isn't ferroresonant either.
thanks
PS i also checked, that UPS isn't ferroresonant either.
rick hart
Senior Member
- Location
- Dallas Texas
Dave,
The UPS that shut down was a 18kVA 120/240 1ph. We converted to single phase to avoid the 4 wire harmnonics problem associated with 3ph UPS. There was dual conversion rack mounted UPS on some equipment but not all; makes it real hard to make the call what caused what. We had a feedback relay recommended by the manufacture installed on the 18kVA and have not had the symptom repeat since.
The UPS that shut down was a 18kVA 120/240 1ph. We converted to single phase to avoid the 4 wire harmnonics problem associated with 3ph UPS. There was dual conversion rack mounted UPS on some equipment but not all; makes it real hard to make the call what caused what. We had a feedback relay recommended by the manufacture installed on the 18kVA and have not had the symptom repeat since.
dave_asdf
Member
- Location
- tampa florida
hmm pretty interesting. LC circuits have always confused the heck outta me, if it's single components in a math problem i can usually figure out what's going on but when pieces of equipment with inductive and capacitive traits start doing what ever it is they do i'm clueless. thanks for the reply.
peter, i hope you patented that idea before you posted it. you could be throwing away millions!
peter, i hope you patented that idea before you posted it. you could be throwing away millions!
- Status