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Thread: Drill Sharpener
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28th June 2014, 07:19 PM #31Philomath in training
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This is my ebay special - Ray suggested that I get it so I could run things like a 110V Biax. I think it was around $70. I must admit I've voided my warranty by opening it and putting a longer supply cord. Originally it was only around 400mm long. Now I have 2m.
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Michael
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28th June 2014 07:19 PM # ADSGoogle Adsense Advertisement
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28th June 2014, 08:18 PM #32
Looks better that I might have guessed for that price, the key thing is the approval.. N16265, must be some of the other ones that look similar are solid state perhaps?
Originally Posted by Chris cba_melbourne
The relevant SAA clause is this one.. from AS 3000:2007
So to power a 110V rated appliance from a 240v input autotransformer is illegal.
Ray
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28th June 2014, 10:34 PM #33Cba
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You are perfectly right Ray. It is illegal using it to power an appliance, that itself is not rated for in our case 240V.
However, the manufacturing, selling and using of an autotransformer is perfectly legal in Australia. The end user is left to find out by himself, if or if not AS3000:2007 4.14.4 is applicable to the particular appliance to be attached.
In this case, the Darex Drill Doctor intended for the American and Japanese market is only fitted with an approval label for 110-120V. It must therefore be hooked up to an isolation transformer. Sorry for having recommended otherwise.
This is an article I found that may help for those considering importing an US appliance to Australia:
http://www.armory.com/~stacey/aus-us-power.html
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29th June 2014, 01:36 AM #34GOLD MEMBER
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29th June 2014, 02:52 AM #35
Hi Cba, Guys,
I don't disagree at all. The whole idea was to provide a quick and dirty way of providing a power source to run the machine.
All the points made by Cba are perfectly valid ! A step down transformer would be the correct way to go, and provide isolation from the incoming supply.Best Regards:
BaronJ.
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29th June 2014, 02:59 AM #36Best Regards:
BaronJ.
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29th June 2014, 08:10 AM #37Philomath in training
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Yes, it is heavy!
The centre tapping can be seen as the white wire in the last picture soldered on to a tag secured to the case using the fuse holder (also visible in the 3rd picture). The factory can't be able to afford coloured wire, this thing is so cheap. It does the job and works but I can't say that the quality of workmanship fills me with great confidence.
Michael
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29th June 2014, 10:15 AM #38GOLD MEMBER
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29th June 2014, 12:50 PM #39Cba
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If you ground the center tap, the the appliance (say a handheld drill) still sees 110V. But if you touch either live wire (say because the power cord breaks), you only get zapped with 55V - which will not kill you, even if you were working barefoot on a wet floor. If you take both live wires each in one hand, then you would of course still feel 110V - but that is rather unlikely to happen inadvertently.
If you think at a construction site, where extension cords get on a daily basis dragged about unfinished concrete floors and around sharp unfinished edges, you appreciate the high risk. On Victoria construction sites the law does not require to use insulation transformers, but all electric tools and extension leads need to be safety tested and tagged every 3 months.
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29th June 2014, 01:26 PM #40GOLD MEMBER
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But(as I understand it), if you have no center tap and no earth connection on the secondary you are isolated of the supply(i.e no potential to ground. To something like 6.5kV if I remember correctly). So to use your analogy you can hold either wire while standing barefoot on a wet floor and you wont get zapped at all. Though you'll still get 110V if you manage to get across both lines. In either case case(of being across both lines) an RCD isnt going to save you. Though I assume the chances of getting across both lines at near as damn it exactly the same time would have to be pretty slim......which maybe why the secondary is earthed.........I guess with an isolated secondary, the bigger the system gets, the more chance of two opposite faults* going undetected and meeting(through someone) increases.
Stuart
*along the lines of two pistol drills one with A shorted to earth, one with N shorted to earth. Either fine to use by itself, just dont pick up one in each hand.
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29th June 2014, 03:20 PM #41Cba
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29th June 2014, 06:26 PM #42
The only reason is that the UK regulations require a center tapped ground. I'm open to either argument, we used to argue this back and forth for years without ever acheiving a consensus... my argument is that if all the mains is floating with respect to ground, you can never get electrocuted by a fault to ground, unless you have two faults, one to ground and one to you. If all mains is referenced to ground ( like in Australia ) then only one fault is required to get zapped... so to mitigate that risk we mandate the use of RCD's .... One reason (perhaps) to reference mains to ground is to minimize lightning strike damage... the discussion then usually moves on to solar storms and coronial mass ejection.. then I make the sign of the cross and slowly back away... Oh.. and most portable power tools aren't earthed anyway. So go figure.
Ray
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29th June 2014, 09:23 PM #43GOLD MEMBER
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Sure the path maybe there but if you're across both lines and happen not to be earthed there wont be any current to earth. No current to earth no imbalance to trip the RCD
Might even make sense for 110V. Not sure I see the point with 240V though.(which is why they are using 110V tools I guess )
I can see what you say about going around in circles lol
Will be a good time to be in the transformer business..... or will it?
Stuart
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29th June 2014, 10:20 PM #44Cba
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29th June 2014, 11:48 PM #45GOLD MEMBER
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