Troubleshooting the UPS

[simon_12]

Hi all

The output voltage of my UPS is approx 300 volts. I have also checked the transistors, they are working properly. When the battery is charging , through main supply, the output voltage is upto the normal value that is 220 volts, but as soon as the main supply fails and the UPS starts , the output voltage becomes 300 volts. Can anyone pls tell me what is the PROBLEM

regards

 

[ghulam_hussain]

actually your ups is square wave and every square wave ups gives 300 output volt
& more without load when you on the load it goes down so you need to add a circuit of pwm which can fix your required voltage.

 

[simon_12]

But , when i previously checked the output voltage of ups , it was around 220 volt on load. There must be some problem with the output voltage of UPS now, because each time when the ups comes on load , the FUSE blows.

Regards

 

[Tahmid]

Hi simon,
Check the feedback section of your inverter. Check any optocouplers and associated resistors and potentiometer. Check the connection of these parts to the oscillator and use a multi-meter to check the output duty cycle and frequency from the PWM chip (SG3524, SG3525, etc.)

Hope this helps.
Tahmid.

 

[kalaianand]

hi
sure there will be problem with the PWM circuitry
in PWM control IC, there are 2 options one for fixed reference(normally 2.5V) and another is varying output voltage variation pot(more than 2.5V). u adjust that pot such that difference between reference and output reference is minimum.at particular poin u will acheive what ever output volotage u want.

 

[Tahmid]

Hi,
Adjust the pot and see if you can vary the output voltage. If you can, good, then set the output to 220V. If you can't you might need to replace some part, most likely the optocoupler (if the circuit employs an optocoupler) or the current limiting resistor at the input of the optocoupler.

Hope this helps.
Tahmid.