what resistor?????

[bambam01]

Hello i have an American 110-120v appliance that i have a voltage dropper for use with 240v UK, however the dropper i have is emitting 122-123v and this making the appliance not function correctly.

The reason why the voltage dropper is emitting this voltage is not because it is faulty, it is because the 240v mains that comes to my home is actually 244-245v due to being in close proximity to the thing at the top of my road that the electricity comes from.

i want to use a resistor to take down the voltage from 122-123v to around 115v but i have no idea what kind of resistor i would have to buy to do this could anyone help me choose which one i would have to use???

many thanks!!

 

[audioguru2]

The value of a resistor and its power rating is calculated from how much current there will be in it and how much voltage there will be across it. You didn't say how much current so we can't calculate a resistor.

An appliance made for 110V to 120V should work fine with 123V since it is only 2.5% high.
Probably you have a simple rectifier that reduces the power (not the voltage) to a heating appliance and it is not made for electronic appliances. You need a step-down transformer instead tat can supply enough current.

 

[bambam01]

Hello

the markings on the label say v 100-120. Hz 50/60 va200 it also says Int 4min./8min. what ever that means i don't know, can current be worked out from this?

the appliance has a small digital display when it is turned on it indicates "hi power" which is the reason i suspect it doesn't work properly it works ok for 20 seconds or so.

so i just need to take some of the volts of it to see if this is the case or not.

Many thanks
                                                       

 

[audioguru2]

Its power is 200VA so if the voltage is 115V then its current is 200/115= 1.74A but is it continuous? You can't calculate a resistpr unless it is continuous.

Int 4min./8min. means intermittent duty cycle of 4 minutes on then 8 minutes off to let it cool.

What is it? What does it do?

 

[bambam01]

hello

its a curring light like what the dentist uses to set white composite fillings... it has a 100 wot bulb.

you press the button and it lights up with a fan to cool the bulb for about 20-30 seconds.

if i can get about 5volts of the mains supply to it i think this would make it work, as it keeps shutting down to soon.

 

[audioguru2]

A 3.3 ohm resistor would reduce the voltage 5.7V. It would get very hot with a dissipation of 10W. Use a 15W resistor and insulate its wires well because it is a shock hazzard.

 

[bambam01]

thanks for your help!!!!!