DC Capacitors

Your vendor is asking you to engage in "Planned Preventative Maintenance".

The purpose of replacing this component despite its apparent functionality is to ensure that your equipment doesn't fail at an inopportune moment. In essence saving you a lot of money, buy spending a little money.

However if you want to save some money, then you can neglect all maintenance. You should get about a years worth of operation.

Just make sure you can blame the equipment failure and loss of production on someone else..

vaidyanathan,

If u want to know expected design life u can refer below acc to your UPS system DC bus voltage.

From my own experience, if its only 5 years there is no need to change the capacitors now. However inspect filter capacitors for any leakage, swelling or discoloration & replace if necessary.

Appendix A: Design Life Calculations for Electrolytic Capacitors

The expected life of these capacitors has been confirmed to follow Aprhenius' equation -- a formula describing

chemical reactions due to dielectric molecules activated by thermal energy. We can calculate L, expected device life

in hours, according to the following:

L = LBASE x 2^((TBASE-TCORE)/10) x Voltage Multiplier

Where:

LBASE = 5,000 hours at 85°C core temperature and rated voltage

TBASE = 85°C

TAMB = 30°C

TCORE = TAMB + TRISE = 30°C + 10°C = 40°C

VR = Rated Voltage

VA = Actual Voltage

Voltage Multiplier = (2.50 - 1.5) VR/VA

= 700/540 = 1.2963 for 540 volts DC bus

= 500/405 = 1.23 for 405 volts DC bus

Solving this we get:

L = 5,000 x 2^((85-40)/10) x 1.2963

= 5,000 x 2^

4.5

x 1.2963

= 146,659 hours (about 16.7 years) for a 540 volts DC bus