Fusible resistor

[pradeeba]

how to select the value of fusible resistor

[esp1]

hi,
Your question is like asking what size fuse shall I use??

Its not possible to suggest a 'fusible link' without knowing more of the application.

If possible, post a drawing of the circuit you want to protect.

[pradeeba]

sorry I cant post the schematics. can u tel me is there any formula to calculate fusible resistor. end application is battery charger. and can u tel me the relation between the  peak primary current?

[esp1]

hi,
I would not normally fit a fusible resistor in a battery charger, a standard, slow blow fuse would be OK.

If its a typical battery charger I would expect a 5 or 10Amp fuse would be OK.

Does the battery charger have a current meter??

>> relation between the  peak primary current?

I'm not sure what you are comparing with peak primary current?

[pradeeba]

output power is 1.25W. we used 10E,1w fusible resistor. it got blowed & diode in the bridge rectifier connected in the neutral path also got blowed.then we used 20E,1W fusible resistor, again same thing happened. can u assist me what to do further? ther e is no current meter. my question was is there any relation b/w primary peak current to choose the value of fusible resistor or fuse. if not how to calculate fuse value.

[esp1]

output power is 1.25W. we used 10E,1w fusible resistor. it got blowed & diode in the bridge rectifier connected in the neutral path also got blowed.then we used 20E,1W fusible resistor, again same thing happened. can u assist me what to do further? ther e is no current meter. my question was is there any relation b/w primary peak current to choose the value of fusible resistor or fuse. if not how to calculate fuse value.

Hi,
If its blowing the bridge rectifier, the problems not with the fuse link.    I would suspect you have a short on the output of the charger. Have you tested across the output terminals with a ohms meter. [ WITH THE MAINS POWER DISCONNECTED]

Also, does it blow fuses when no battery is connected to the output??

Also, is the charger rated at the same voltage as the battery, example:  12Vcharger, 12Vbattery??

Also, is the input mains selection for the transformer set for you local mains supply voltage???

[pradeeba]

hi,
Actually there are 8 boards. 6 are working fine. only 2 boards are giving the problem. fuse blows when no battery is connected to the output. power suuply o/p is 5V & battery for battery 3.6V is needed.

[esp1]

The 2 boards that are blowing fuses, have you done a resistance check on the output pins.
I sounds as though you have short on the boards, especially as they blow with no battery connected.
Do you have a circuit you can post, it will make it easier to suggest a repair.

Are the 3.6 Vbty  for mobile phones?

[Ante]

Are the output connectors switched?