ups

[peteludman]

Hi all

I need someone to help me

i have just done the inspection and testing on a industria property which has a generator and ups batts.

the ups batts have protection by 250a fuses but the neutral have 250A fuses to, if the ups was running and there was a fault which has a 50% chance of blowinng the neutral fuses so there is still 415 v between phase and earth


am i just looking for faults with this or should the neutrall not be fused on this instalation i know a neutral should not be fused

 

[Sintra]

Hi all

I need someone to help me

i have just done the inspection and testing on a industria property which has a generator and ups batts.

the ups batts have protection by 250a fuses but the neutral have 250A fuses to, if the ups was running and there was a fault which has a 50% chance of blowinng the neutral fuses so there is still 415 v between phase and earth


am i just looking for faults with this or should the neutrall not be fused on this instalation i know a neutral should not be fused

Is this a 3 phase AC supply to the UPS that has the fused neutral or a DC output?

 

[ian.settle1]

Neutrals have not been allowed to be fused under the IEE regs since 1955 think you will find it is the NEGATIVE side of the batteries which are fused.

UPS work by A/C coming in then rectified into DC , the DC output from the rectifier is then converted back into AC via an inverter for the output of the UPS.
A battery charger circuit is also connected from the AC input to charge the batteries which in the case of a mains failure will supply the inverter.

You would not get 400v between phase and earth only 230v if you had 400v then you would also have a short circuit between phases.

 

[peteludman]

thanks

so what you are saying is its ok for the dc to have fuses on neutral ?

and sorry i know you can only get 230v phase to earth just being dumb last night it was late and i was tired (honest).

you know your stuff about ups then

 

[cossie400]

Hi all

I need someone to help me

i have just done the inspection and testing on a industria property which has a generator and ups batts.

the ups batts have protection by 250a fuses but the neutral have 250A fuses to, if the ups was running and there was a fault which has a 50% chance of blowinng the neutral fuses so there is still 415 v between phase and earth


am i just looking for faults with this or should the neutrall not be fused on this instalation i know a neutral should not be fused

Hi,

For a start its Positive and Negative Being DC, Not phase and neutral that you get in AC.
Depending on the amount of "strings" and amount of batteries per "string", there could be upwards of 500volts being produced.