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Author Topic: Electrician question on power ratings.  (Read 2977 times)

tigertiger

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Electrician question on power ratings.
« on: May 15, 2016, 02:13:20 PM »

There is an electical appliance rated as
380 volt, 16 amp and 2200 Watt.


There is an option to step the voltage down to
220v, 16 amp.


My question is, will the wattage also change?


TT
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g6swj

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Re: Electrician question on power ratings.
« Reply #1 on: May 15, 2016, 02:57:14 PM »

Calculations:


Watt = volt x amp
Amp = watt / volt
Volt =  watt / amp


So the original ratings 380 volt, 16 amp & 2200 watt do not seem to equate. What is the appliance?
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petermun

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Re: Electrician question on power ratings.
« Reply #2 on: May 15, 2016, 03:31:12 PM »

The main question is: Is it vac or vdc?  Pete
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Corposant

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Re: Electrician question on power ratings.
« Reply #3 on: May 15, 2016, 05:31:22 PM »

TT

Assuming AC! Your information presumably comes from the plate on the appliance. Normally one would expect mention of only wattage and voltage - wattage being an indication of energy consumption. The 16 amps would be a recommendation for the supply circuit (very generous!).

As g6swj points out, running off 380 volts the current draw would be approx. 5.8 amps and running off 220 volts, 10 amps.

The mention of 380 volts implies, to my mind, a three phase supply - which (assuming the appliance has a motor) would imply two sets of windings - for three phase or single phase operation.

If you can supply more information about the appliance, I'm sure you will get advice from the forum experts!

Mike
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NFMike

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Re: Electrician question on power ratings.
« Reply #4 on: May 15, 2016, 05:49:56 PM »

Is that really 2200W, or is it 2200VA?

NoNuFink

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Re: Electrician question on power ratings.
« Reply #5 on: May 15, 2016, 08:05:27 PM »

3 phase motor?   IIRC  380V is the line voltage for a 220V system
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TomP

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Re: Electrician question on power ratings.
« Reply #6 on: May 15, 2016, 10:26:11 PM »

380v I would expect to be 3 phase, 16a will be recommended protective device rating 2200w is the power it will pull. If it is 3 phase current draw is worked out by power divided by 1.73x voltage X power factor roughly 4A at that voltage @ .8 power factor. If it is a 3 phase motor you can get an inverter for single phase but it's cheaper to replace the motor. If you reduce the voltage to that motor power will stay the same but current will go up, if you do have 3 phase 220v it will pull approx 7A @ .8 power factor, and might need a 20A protective device??
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tigertiger

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Re: Electrician question on power ratings.
« Reply #7 on: May 18, 2016, 03:23:39 PM »

Sorry for the delay in reply I have been away for a few days.


The machine is an industrial dust extractor. In China industrial voltage is 380v normally. 16A was the recommended circuit, not the rating (sorry).
In China there are usually only two ratings of circuits/plugs/sockets etc. 16A and 10A. I have both in my workshop.


The manufacturer offered the machine, adapted at 220V for those who do not have 380v.
I chose this machine as it is half the price of the nicer looking, 1500W, non-industrial version; and the footprint is only 10cm bigger for length and width.
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Corposant

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Re: Electrician question on power ratings.
« Reply #8 on: May 18, 2016, 05:07:40 PM »

Hi TT

Presumably your question is really "Which supply circuit should I use?" The manufacturer recommends 16A, so that would seem the obvious choice (personally I think the 10A one would be fine - most unlikely to drop out the breaker/ blow the fuse.).

The slightly more worrying thing, when reading your post in March, was that there was no mention of an earth connection - only a brown and black wire. Dave M and Brian60 gave sound advice at the time.

Slightly surprising that the manufacturer offers a 3 phase machine "adapted" for single phase operation.

Mike
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Netleyned

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Re: Electrician question on power ratings.
« Reply #9 on: May 18, 2016, 05:15:19 PM »

I think 16 Amp is the best for a 220V 2200W  appliance (10A)
Startup current may be a bit more than !0A


Ned
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tigertiger

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Re: Electrician question on power ratings.
« Reply #10 on: May 19, 2016, 03:10:42 AM »


Firstly, thanks to everyone for your answers  :-))

My question was also related to performance/power.
Will the machine still perform at 2200w. This would affect airflow and subsequently extraction.




TT
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Corposant

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Re: Electrician question on power ratings.
« Reply #11 on: May 19, 2016, 10:22:00 AM »

Sorry TT - so much advice but nothing to tell you what you actually want to know!  {-)

Without knowing how the machine was adapted for 220V operation (e.g. did they fit a different motor), I don't think its possible to give a theoretical answer. The simplest option would be to ask the manufacturer - but the answer may depend on whether you spoke to a salesperson or a technical person!

One thing you can do is measure the current draw with an (AC) ammeter and apply Jonathan's calculation (which as Plague points out will give you VA!). This, however, will not tell you how the machine performed on 380V!

Having taken delivery of the machine (and presumably paid for it), you obviously want to know whether to send it back and buy the prettier, more expensive one! - sorry can't help you there.  :((

Mike
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inertia

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Re: Electrician question on power ratings.
« Reply #12 on: May 19, 2016, 11:00:59 AM »

If you have a 380v (3-phase?) supply and the extra money then buy the industrial one. If not then it's Hobson's choice, irrespective of any other considerations. Makes sense to me anyway.
DM
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inertia

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Re: Electrician question on power ratings.
« Reply #13 on: May 19, 2016, 12:27:44 PM »

If you have a 380v (3-phase?) supply and the extra money then buy the industrial one. If not then it's Hobson's choice, irrespective of any other considerations. Makes sense to me anyway.
DM
OK - so you've already bought the 220v one.  :embarrassed:
Logic says that if the 380v one has the same performance (aka power) as the 220v version but is twice the price then they ain't gonna sell many of 'em. Also something tells me that if you put a lower voltage motor into an existing machine then it is not going to be as powerful, all other things being equal. Tom's maths is impressive and undoubtedly bang on the mark (oops - sorry, Mark...) but applied commerce and a touch of cynicism should provide the same answer without the pain of research.  It usually works for me.  O0

All you need do now is forget that there ever was an alternative to the one you bought, or feel a little smug that practically no other modellers have an industrial dust-extraction system in their workshop anyway!  <:(

DM
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NFMike

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Re: Electrician question on power ratings.
« Reply #14 on: May 19, 2016, 03:01:39 PM »

Firstly, thanks to everyone for your answers  :-))

My question was also related to performance/power.
Will the machine still perform at 2200w. This would affect airflow and subsequently extraction.

TT

If it's a synchronous motor then it will try to run at it's natural speed, which will spin the fan at something like the correct speed too. However, that will require the same power regardless of voltage which means that on the lower volts it will have to draw significantly more amps as described by tomp in post #6 above.
If it's not a synchronous motor then the lower volts may mean it runs slower but drawing similar current, and obviously that will impact the fan performance.

microgyros

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Re: Electrician question on power ratings.
« Reply #15 on: May 19, 2016, 09:59:53 PM »

The reasonable enough factor of 1/3 power reduction came upon a first search hit http://www.finewoodworking.com/workshop/qa/three-phase-machines-in-shop.aspx

I am reading the information supplied by TT to likely mean that a 2.2 kW 3-phase (induction motor) extractor is available as a factory assembled 220v version which has a bolted on panel with a single to 3-phase start/run circuit. The defect in Martin's extractor was a loose wire within what looked like a home made unit.  Link?


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