Which transformer

[jedimistress]

I bought my boyfriend a cement mixer for Christmas. It needs a transformer as it is a 110V mixer.

I know nothing about this. I have seen one advertised from 230V to 110V. Does this mean he can plug it into the mains? I just need to enable him to connect it to standard supply. Any advice welcome, and how much should a decent transformer cost? Anything else a bonus as I really can't understand them. Why is it a 110V in the first place? etc

[MustafaTinkl]

A 230/110 V transformer will do fine. It should look like this . It should cost �60 - �70. The reason for 110V is safety, 230/240V kills, 110V does not.

[MustafaTinkl]

That link does not seem to be working, lets try this http://tinypic.com/j9rdzt'

[MustafaTinkl]

Hmmm. Tinypic does not seem to be working for me tonight !! I'll now try this .

[MustafaTinkl]

Success !! The blue wire from the transformer just plugs into the mains with the same plug + 13 amp fuse that you have on a kettle. The red knob resets the transformer should your b/f put too much cement and sand into the mixer and overload the transformer. The 110V plug from the mixer goes into either of the two yellow 110V sockets (they have hinged caps which lift up). Thats all.

[qapmoc]

Hi mustafatinkl, Sorry to disagree with you a bit about the lethal effects of various voltages, If you are well connected to earth (standing in water for example) then 230 will probably kill you if you hold the live wire, 110v will also probably kill you if you hold the live wire, but the chances of surviving a chance contact is much better if the voltage is lower. Yeah I know this might seem like a small point but your answer could encourage somebody to think that 110 volts is safe to touch etc...when it is still switched on.
In fact we had somebody locally who died from using a electric welder in a wet environment and the voltage from those is around 45v open circuit.

[buildersmate]

An oft stated misconception. The voltage regarded as 'safe' by the Institute of Electrical Engineers is somewhere just under 30 volts.

[sddsddean]

Actually the voltage isn't that important; its the current that kills you. Anyone ever got a belt off a spark plug lead when servicing the car? Thats about 12000 volts!

[sddsddean]

Just looked on 'how stuff works' and they reckon a spark plug voltage can be anywhere from 40000 to 100000 volts, but there is naff all current which is why its 'safe'.

[jedimistress]

My dad said if I read the output I should be able to choose the transformer. The output reads 1.5kW. I have seen a few double plugged transformers with output of 3kV. Would this mean 1.5kV in each plug and not 3kV through each one?

I don't want to get it wrong. Thanks.

[qapmoc]

I think you already got it slightly wrong because you put Kv and not Kw in your last question, yeah I know somebody will say these are small points but when you are making technical questions you have to make an effort to get things right or you can end up buying the wrong stuff or paying a lot more than you need to.

So if a device takes a 1.5Kw load then you need a 1.5Kw or more transformer, I suggest that for this application where overloading at starting might happen often then at least 3.0Kw would be best (a motor can take up to six times its running current when starting).

The transformer rating is the total output regardless of how many plugs there are. Each plug has its own current rating and a 1.5Kw load at 110v is 13.7Amps so you must choose a transformer with at least 16Amp plugs fitted, 32Amps plugs would be even better but is not essential.

[MustafaTinkl]

3 KW (or 3000 W) is the total output of the transformer and can be through either one or both of the outlets - it is not divided between outlets. Any number of devices can be connected to either one or both outlets so long as all of the individual outputs of the devices when added together do not come to more than 3KW. The transformer can have two 16 amp outlets on one side, or they can be on opposite sides. 16 amp outlets are standard for these small transformers. These transformers are heavy things weighing more than a quarter of a hundredweight. In your case a double plugged 3KW transformer is best, simply because there will be more than sufficient output for the mixer and it will not run overhot and burn out (all of them become warm in operation). There is little difference in cost between a1.5KW and a 3KW unit, but the 3KW will probably last "forever". As I have previously said and again repeat the purpose of stepping down the volts is safety. At the 240V socket you should have an RCD device (not expensive from any electrical supplier). The 240V lead to the transformer should be kept as short as possible (do not use extension leads if avoidable). All extension leads should be between the transformer and the mixer, so as well as the transformer you may also need to purchase an extension lead or two with 16 amp sockets and plugs at each end for your boyfriend. The RCD will ensure that in the event of anything going wrong the current will be interrupted in a fraction of a second, which, together with the stepped down volts through the transformer, will very greatly reduce the chances of your boyfriend receiving a dangerous electrical shock.

[MustafaTinkl]

PS. The reason that I recommend 2 16 amp outlets is that, as well as the obvious of being able to connect other 110V tools whilst using the mixer, occasionally (not often, but it happens) one of the outlets unnacountably runs hot and burns out. If this happens, the transformer will continue to work perfectly well with only the one outlet.

[jedimistress]

Thanks Mustafatinkl.

Your answers are lovely and clear. I know I might write out the wrong things a little when asking but I figured someone who knows what they are talking about, or what I am talking about, would understand my mistakes.

At least I know that k for kilo is always a little k. V, W and A should have capitals. I remember that much from physics.

I will opt for the 3.3kVA output double socket site transformer. This sound ok? Thanks again. Lynsey

[jedimistress]

Thanks everyone else too for your replies.

[Evorg Enaj]

The one you have selected will be absolutely fine, Lynsey. Happy mixing, and a Happy New Year.

[stanleyman]

The 110 volt output from a transformer has a centre earth tapping giving only 55 volts to earth. This is much safer than 230 or 110 volts with an earth fault.