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Author Topic: Inverter rating for Motor surges  (Read 5629 times)
timbo
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« on: December 05, 2007, 11:59:49 AM »

I am looking to buy a 48V DC to 230V AC TSW (true sine wave) inverter to run my house.

I use less than 12 kWh/day (500W ave.) but occasionally up to 1500W during the evening....thats the easy bit.

The 1kW inverter supplied with my turbine trips out and needs resetting if I connect ANY motor to it (fridge/freezer/well pump/washing machine/vacuum cleaner).

I know there is a starting surge on any motor but just how big is it?

Also, the shape of the surge? in terms of peak current and power?

The Victron/studer etc inverters all seem to have surge ratings of double the continuous rating for a few minutes, but I think that a motor surge could, (for a few mains cycles), easily exceed twice the running power of the motor.

The well pump is rated 1kW and the vacuum cleaner 1400W.

What is your experience?

Tim.


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4m^2 wet solar panel, wood stoves. 10kW roof mount P.V. grid connected.
6kW Kingspan turbine expected soon.
RichardKB
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« Reply #1 on: December 05, 2007, 12:11:21 PM »

Hi see the graph on this link.

http://www.lmphotonics.com/m_start.htm

Rich
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tony.
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« Reply #2 on: December 05, 2007, 12:46:50 PM »

direct on line charging can be up to 9 times the running current : depending  on the motor.
star delta can be up to 5 times Undecided

regards
tony


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timbo
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« Reply #3 on: December 05, 2007, 01:56:37 PM »

Hi,

Thanks, I am not surprised by these figures of a current suge of x5 to x9.

Does this mean however, that a 10kW inverter is needed in any home with a 1200W vacuum cleaner OR, the specification on a typical inverter is incomplete and they can cope with very high but brief surges, without tripping off?

What do people here use and do they have problems with inverters tripping out when they clean the house?

Tim.
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4m^2 wet solar panel, wood stoves. 10kW roof mount P.V. grid connected.
6kW Kingspan turbine expected soon.
tony.
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« Reply #4 on: December 05, 2007, 04:08:53 PM »

I wouls say some of the better inverters ie xantrex and other brand names who have a proven ttack record and a technical help dept would help.

I imagine the biggest inverter most peopple in the uk would use be 3kw.
Dont quote me on it Grin

tony
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billi
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« Reply #5 on: December 05, 2007, 10:09:26 PM »

Hello

 the victron units i use  havent had a problem jet  .... will see  (but have two  in parallel  of 3 kw )

i think they can do even more then double for the second or so for starting....  example pump

but not too sure  they did indicate on the leds  overload but still were fine ...

 perhaps get one inverter that you can add one of the same later to double or tribble for three phase...

regards Billi



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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
timbo
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« Reply #6 on: December 05, 2007, 10:21:29 PM »

Thanks, that Victron 3000W unit looks very nice indeed. At the moment I am torn between that at 900 and the COTEK 2000W at 430.

:-(


Tim.
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4m^2 wet solar panel, wood stoves. 10kW roof mount P.V. grid connected.
6kW Kingspan turbine expected soon.
billi
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« Reply #7 on: December 05, 2007, 10:29:07 PM »

hi

here they have specials on victron

mainly  inverter/chargers combis ( i have two )  so for the same monney you get a charger as well to connect a small generator or the grid to top the battery and assist the inverter when more power needed

all the best

http://www.onboardenergy.com/acatalog/victron_special_offers.html



sh :-Xt forgot you need 48 volt option sorry...
« Last Edit: December 05, 2007, 10:57:38 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
camillitech
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« Reply #8 on: December 06, 2007, 08:04:08 PM »

Hi timbo,

if you have a washing machine unless you want to run round switching things off when you use it i would say 2000w is too small, there seems to be no proper standard for rating inverters so i would steer clear of any manufacturer that does not give you surge data, and continuous data, some manufacturers seem to think that 20mins is continuous Huh with inverters you get what you pay for. from personal experiance studer and trace are what i would choose and i,ve heard good reports of outback, victron and sterling, all these people supply proper data to back up there claims. I run a trace 4.5kw 48v it will produce 4.5kw all day, 5kw for 10 or 20 mins, 7kw for a couple of mins and it will surge to 12kw, I think the others are not quite as good but comparable. the cheaper ones however would be calling themselves 7 or even 12kw models with performance like this.

good luck, paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
timbo
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« Reply #9 on: December 07, 2007, 08:47:59 AM »

Thanks for the useful advice.

I have just ordered a Victron 3000W inverter. It seemed to say good things about surges although none of the top makes really seem to have addressed the real life surges you will see in a house in their specifications.

Tim.
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4m^2 wet solar panel, wood stoves. 10kW roof mount P.V. grid connected.
6kW Kingspan turbine expected soon.
RichardKB
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« Reply #10 on: December 07, 2007, 12:20:14 PM »

The types of thing that may cause problems is if you are using the washing machine which is heating the water and then the fridge/freezer decides to start up, or you have an old CRT TV or monitor that when powered on does an automatic degauss this may tip the inverter into overload.

Rich
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camillitech
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« Reply #11 on: December 07, 2007, 06:22:44 PM »

Thanks for the useful advice.

I have just ordered a Victron 3000W inverter. It seemed to say good things about surges although none of the top makes really seem to have addressed the real life surges you will see in a house in their specifications.

Tim.


i don't think you'll be dissapointed timbo Grin

good luck, paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
billi
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« Reply #12 on: December 07, 2007, 10:51:10 PM »

hi timbo

nice one

in case you need help or advice to connect it or other things----- the victron helpline or customer support on their website is very good

much more easy ----better than the company i bought it from...
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Phil
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« Reply #13 on: January 18, 2008, 05:21:40 PM »

Yes I also use a Victron and have had no problems unbeatable at that price !
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