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inverter power
By guruji, Section Controls Posted on Tue Jun 10, 2008 at 06:37:09 PM MST
300w inverter

Hi guys I have a 300w to 500w inverter.I tried to run my washing machine on it rated 340w with 200amp battery bank but invain.Sometimes I was thinking cause I need a bigger fuse.
Any help please?
Thanks

inverter power | 12 comments (12 topical)

Re: inverter power (3.00 / 0) (#1)
by boB on Tue Jun 10, 2008 at 01:03:25 PM MST

Where the heck you find a 340 Watt washing machine ?

boB

Re: inverter power (3.00 / 0) (#12)
by elvin1949 on Tue Jun 17, 2008 at 08:01:21 PM MST

boB
Mine is 720 watt.
1953 Kenmore wringer washer.
Going to turn it into a gas powered machine.
later
Elvin

[ Parent ]

Re: inverter power (3.00 / 0) (#2)
by Opera House on Tue Jun 10, 2008 at 01:49:57 PM MST

When motors start, the initial current is usually that of the rated locked rotor current. I wanted to use an inverter on a small fridge. It only used about 100 watts running, but initial current is about 17A. A 500W inverter goes into instant shutdown since it thinks it detects a short. That 100 watts takes a 1,000W inverter minimum to run it. You likely need one rated at 200W.

Re: inverter power (3.00 / 0) (#3)
by Opera House on Tue Jun 10, 2008 at 01:51:29 PM MST

That should read 2,000 watts.

Re: inverter power (3.00 / 0) (#4)
by DaveW on Tue Jun 10, 2008 at 01:57:35 PM MST

The start surge for a motor driven device may be 4 to 7 times the run load. You have to overcome the start surge to get the device to run. Overfusing the inverter will most likely ruin the inverter, may start a fire, and still probably won't develop enough output current at the right voltage to do any good. Overfusing any device is an invitation to problems, overfusing an inverter is a bad idea.
DaveW

Re: inverter power (3.00 / 0) (#5)
by richhagen on Tue Jun 10, 2008 at 11:33:38 PM MST

Don't increase the size of the fuses on the inverter! They are there to protect the circuit and should have been sized by the designer to keep the device safe. If you increase their size the most likely result will be a ruined inverter with an additional possibility of property damage or personal injury.

I have an 1100 watt sine wave inverter that will not reliably start my washer - although I can generally make it work with a large enough capacitor across its leads. Once running the washer only draws about 250 Watts or so, but starting the motor takes many times a multiple of that and I don't see any way that small inverter of yours is going to accomplish that.

My washer runs fine on my 4000 watt Xantrex SW4048 inverter though. I suspect that any of the Xantrex SW or XW series inverters in your local flavor of AC would work as well as any of the Outback FX or VFX inverters, but they are likely much more expensive than your small inverter. Rich
'A Joule saved is a Joule made'

Re: inverter power (3.00 / 0) (#6)
by guruji on Wed Jun 11, 2008 at 05:04:16 AM MST

Hi DaveW is there an electronic device to overcome the start surge that you were mentioning?Or can one put a big capacitor to overcome it?
Thanks Dan Fink for publishing this and you guys for response.

Re: inverter power (3.00 / 0) (#7)
by Opera House on Thu Jun 12, 2008 at 02:16:07 PM MST

Capacitors just won't do it, especially on the input 12V. I did a little experiment with a 500W inverter by placing a bank of 12,000uF on the high voltage of the inverter. This capacitor alone is enough to light a 100W lamp for several seconds. That didn't give enough surge to start a 100W motor. The inverter shut down when it detected a current surge. Even adding an extra delay didn't work. I decided it wasn't worth going further. I purchased a 1200W inverter for $17 and will see how that works.

Re: inverter power (3.00 / 0) (#8)
by joestue on Thu Jun 12, 2008 at 02:53:48 PM MST

the thought occurs to me that a high impedance 12v supply would have a better chance of starting the motor, if the UVLO don't turn off the inverter. the reduced voltage would cause a likewise reduction of output V and I. many of these 12 volt inverters turn off at 10.6-8, to protect the lead acid.

if you can find the output current transformer, you can increase the typically 10uF cap after the rectifier to 50 or more. if the inverter measures current in real time, you can't do much, especially if it is uProc controlled.

the 12v side fets won't mind the extra current, provided normal operating temp isn't extremely high....

[ Parent ]

Re: inverter power (3.00 / 0) (#9)
by richhagen on Thu Jun 12, 2008 at 03:03:15 PM MST

It seems to me that capacitors would largely be useful in making up a bit for slightly undersized cables from the battery to the inverter during the start up surge if sufficiently sized. They (24,000 microfarad at 75V) did have a noticable positive impact on motor startup in my washer using the 1100 watt Exeltech, but only marginally, and not consistently reliably. It would not start it at all without the added capacitance. That inverter has small, maybe 10 guage leads to it. Rich
'A Joule saved is a Joule made'
[ Parent ]

Re: inverter power (3.00 / 0) (#10)
by not benjamindees on Thu Jun 12, 2008 at 08:57:42 PM MST

"I did a little experiment with a 500W inverter by placing a bank of 12,000uF on the high voltage of the inverter."

Are you saying a capacitor of that size on the inverter output still wasn't able to start a 1/8 hp rated motor?

Because I can see how putting a capacitor on the input size would provide little benefit. A battery bank large enough to power a washer for any period of time should be able to source enough current to start a typical washer motor. As richhagen said, only undersized cables could really cause a problem on the input side.

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[ Parent ]

Re: inverter power (3.00 / 0) (#11)
by guruji on Mon Jun 16, 2008 at 11:11:19 AM MST

Hi Benjamin so if I add capacitors to the motors I can lower consumption too?
When you said capacitors to invertor where they should be installed?
Thanks.

inverter power | 12 comments (12 topical)

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