Over the past few weeks I have noticed some issues with my UPS when the power goes out and our Inverter kicks in. Earlier then the mains power came back when the UPS was on inverter it would loose power for about 1/2 a second which is enough to restart any computer connected to the UPS. So I took it for servicing and the guys over there increased the sensitivity of the UPS and it looked like it worked for a while…
Two days later I noticed that when the system was running off the inverter power it was having trouble, basically it looked like the UPS was cutting to battery and then back to mains ~ two times a second. Spoke to the UPS people and they said that it might be a problem with the inverter voltage/frequency and asked me to reduce the sensitivity or connect it to a socket without the inverter. So I bypassed the inverter and connected it directly to the mains.
Now the problem is that there is one hour loadshedding in the morning and if I am running the computer the UPS drains out in 20 mins and shuts down. Which was a pain. So I installed the UPS control software on my desktop and reset the sensitivity back to medium. Then I was just playing with the various options and I saw that the incoming voltage was 280 Volts (Normal voltage in India is 220 Volts) when the inverter was running.
I thought that it might be a bug in the software and it was probably showing the wrong voltage so I took my digital multimeter out and used that to measure the voltage. Sure enough it was 280 volts. Immediately disconnected the UPS from the inverter line and connected it directly to the mains line.
Spoke to the inverter people today (actually dad spoke to them) and they tried to tell me that the inverter was giving a cosine wave instead of a sine wave so thats why the voltmeter was reading the voltage incorrectly and that its supposed to give 280 volts and if we put more load on it then the voltage would go down to the correct value. Told them to stop BSing and send someone over to look at it. So a tech is coming tomorrow.(Hopefully).
Till then all my equipment is off the inverter line. Hopefully this will get fixed soon.
PS: Incase you are wondering; an inverter is sort of like a UPS but for the whole house. The one we are using is 1400 KVA. You also get ones with larger capacities that can support AC loads etc.