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how to design fuse for 20watts and 40watts cfl bulb

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neezan

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Actually i don't know how to desing fuse for 20 watts cfl bulb. What i am doning , i have supply 220v to a room and the condintion is in a single room it can use a cfl bulb of 20 watts only, if a person in a room use cfl bulb more than 20 wats it should blow the fuse, acordind ti my basic knowledge i have calculate fllowing:
give,
V=220volts
P=20 wats
consider power factor for cfl=0.6
therre fore current flow throug circuit is I=20/(220*0.6)=0.1515Amps current
CAN ONE FIND 0.15 Amps fuse in market? Acyually i canot find it..
how to design this 0.15 amps fuse?
 

0.16A (160mA) is a standard rating.

Don't forget the CFL draws a surge current when switched on so use a time-delay fuse.

Brian.
 

HOW ONE CAN MAKE OR MANUFACTURE time-delay fuse?
 

neezan said:
HOW ONE CAN MAKE OR MANUFACTURE time-delay fuse?
Click to expand...
Use a 555 timer circuit to switch ON a relay after 2 seconds the switch for the CFL is switched and wire in such a way that the fuse comes in series to the CFL circuit...Cheers
 

You can try with a 0.15 to 0.18 A/250 V polyfuse. An thermal circuit breaker with similar nominal current should also work.
Both are at risk of being damaged, if the bulb fails with a short.

By thw way, are working as a prison warder?
 

Why not just buy one - 160mA time-delay fuses cost almost nothing and are easy to get hold of, it is a standard 'off the shelf' rating.

Are you really asking for a fuse or is it a current limiter you want? I mean, do you intend to cut the power if 20W is exceeded by blowing the fuse so it needs replacing or do you want to prevent more than 20W load being drawn by dropping the voltage so the current is limited to 150mA? If the latter, be careful, CFLs misbehave if the voltage is too low.

If it is a prison cell light - consider LED lights, they are more reliable, use safer voltage, use a voltage less suitable for other purposes and are relatively non-toxic.

Brian.
 

i am really asking for a fuse that cuts the power if 20W cfl bulb is exceeded by blowing the fuse so it needs replacing?
Is it possible to turn of the circuit when load is greater than 20W?And if the load is 20W cfl bulb or lesser the ciruit is turn on and supplyes regular power supply?
Nijan

Added after 23 minutes:

Can one any tell me that wheather my calculation for 20 watts cfl bulb is correct? Also plz tell me what is the fuse required for 40watts fuse....
 

Hi,
There is something called resettable fuse which cuts off the supply if current flow is greater than the rating and after some time current is allowed to flow again if it is within limits.
I got some from Tyco from Delhi. There are some called "Polyfuse" from Littelfuse and Bourns and some other manufacturers as well.
en.wikipedia.org/wiki/Resettable_fuse
Hope it helped.
Tahmid.
 

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