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### Power Inverter Shut Down

09/17/2012 4:52 PM

Hi,

I have a solar power system of 300W.Battery bank of 12V/200AH and an inverter of 600W power output.The inverter specs are:Power output Cont.) =600W,Peak power =1200W,Nominal input voltage 12V(10-15V). Nominal output Voltage=220V,f =50Hz,output waveform=modified sine wave,Eff=85-90%. Today I have bought a new fridge with the foll. specs:Total eff.volume(L)=206, Rated voltage=220-240V, f=50Hz, Gross input power 80W,Consumption=0.81kWh/24h. When I have connected it to this inverter, it switches off automatically (I have tried many times), from the inverter's manual I have, if this happen, it means that the connected device has more wattage than the inverter's output power or when the temp. of an inverter exceeds 60 degree due to prolonged use. Pls help.

Thobias

Pathfinder Tags: MODIFIED SINE WAVE off grid POWER INVERTER
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Guru

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#1

### Re: POWER INVERTER SHUT DOWN

09/17/2012 5:32 PM

AC motors like the one in your fridge need sinusoidal or sinusoidal-like (modified sine) alternating voltage from a source capable to provide more than 10 times the motor rated power, to give you a reliable motor start. My quess is that your inverter is not up to the task for either of the above. S.M.

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Good Answer (Score 2)
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#5
In reply to #1

### Re: POWER INVERTER SHUT DOWN

09/17/2012 11:02 PM

sorry sm, i did'nt mean to repeat your ga.

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#13
In reply to #1

### Re: POWER INVERTER SHUT DOWN

09/18/2012 8:51 AM

OK sir,

The inverter's manual recommends that for inductives loads, the cont. power of an inverter should be at least 3 times cont.power of the device to be connected on it.But what does it mean when the fridge manufacturer prints that the cross input power is 80W? while the compressor itself is rated as 1Hp,that's 750W!

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#14
In reply to #13

### Re: POWER INVERTER SHUT DOWN

09/18/2012 9:29 AM

Either there is a missprint or a zero missing from the nameplate (did not read it properly?). 800W for a 1hp compressor motor(That is if the name plate is saying 1 HP electrical consumption, and not 1 HP cooling (old facion jargon...).

If 800W, then 2,400W would be needed as per your manual! More likely for a fridge: even if the 1 HP is cooling power. 80 W is really a very very small fridge.

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#18
In reply to #14

### Re: POWER INVERTER SHUT DOWN

09/19/2012 6:18 AM

Thanks,

Let me put down all the name plate data at the rear side of the fridge:

Climate: WRZS-208.SX

Total effective volume(L): 206

Freezer volume(L): 69

Rated voltage: 220-240V AC

f :50Hz

Gross input power: 80W

Star lebeling:4

Consumption: 0.81kWh/24h

Freezing capacity(kg/24h): 2

Refrigerant charge(g): R134/81.

But the compressor on it is rated: 1hp=750W.If the Gross input power is 800W,the consumption can't be like the above,even if there is a thermostart!, for 24hrs.Let me add this,Our electricity utility company,rate the refr.at 300W and this is an old estimate,nowadays there is more efficient fridge.Sorry for putting this:The money I have paid for this device is US\$ 325.

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#19
In reply to #18

### Re: POWER INVERTER SHUT DOWN

09/19/2012 6:28 AM

"Consumption: 0.81kWh/24h"

The consumption figure, on face of it, appears to be erroneous. A fit case to take-up with the manufacturer & energy star labeling authority.

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#20
In reply to #18

### Re: POWER INVERTER SHUT DOWN

09/19/2012 6:29 AM

Do you have the means to actually measure the current?

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#23
In reply to #20

### Re: POWER INVERTER SHUT DOWN

09/19/2012 7:18 AM

Yes, I can do this,But to take this device somewhere else.At my home is off grid.

The system is operating smoothly,without this fridge.

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#25
In reply to #23

### Re: POWER INVERTER SHUT DOWN

09/19/2012 7:46 AM

If feasible, hire a bank of 24 V battery, have it connected in parallel to the existing battery & take a test run. While you are at it, measure the starting & running current. If found successful, you can weigh your future options.

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#27
In reply to #25

### Re: POWER INVERTER SHUT DOWN

09/19/2012 8:46 AM

Intriguing.

You sure about that? 24V parallel 12V.....

What's your proposed objective?

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#30
In reply to #27

### Re: POWER INVERTER SHUT DOWN

09/19/2012 10:14 AM

I think I am getting old faster. My short term memory, now it appears, is failing me. Must see my Doctor sooner.

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#28
In reply to #23

### Re: POWER INVERTER SHUT DOWN

09/19/2012 8:48 AM

I'm guessing that taking the fridge elsewhere is a bit of a hassle.

Is there no generator at your location? How about a TSW invertor you could borrow?

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#24
In reply to #18

### Re: POWER INVERTER SHUT DOWN

09/19/2012 7:36 AM

Thobias,

I tried to google the model WRZS-208 and it seems that it is a Westpoint Refrigerator make (Originally??). But the makers now are in China. It has been replaced by the model 240 litres, which is being supplied without compressor and pump (?). I think that the Chinese produce and supply the Fridge as such, in minimum quantity, for some OEMs to add the compressor etc. The price quoted for such delivery is ~ US\$33.

Now to come back to your issue: Since I could not get any electrical specs for your model and neither for the 240L model, And considering that maybe the nameplate on your fridge is original, I am more inclined to believe that the compressor was added to the fridge later, and might be too big! (replaced the original size ???).

1- As the details show that the 80W is consistent with the cooling capacity claimed,

2- Can you see if the compressor has any spec stating the voltage and the Amps?

3- Reasons: An 80W consumption will, at best, give 150 Wh cooling or nearly 500 BTU/h. If the fridge efficiency is 50%, then you would expect the 2Kg of freezed water.

4- A 1hp (Electric) at 240V will have an Amp rating of ~4A, and probably will draw a peek of 12 to 20 A (depending on installation and make...) when starting, for ~ 2 seconds if all is well (2400 to 3800 W).

5- Check: If the fridge runs OK when on the Mains Grid, Measure the Peek demand with a digital meter, and the running Amps.(Without the Inverter, directly on the Mains power supply). This will definitely conclude the required Amps and confirm wheteher the inverter you have at hand will be able to cope with it.

--- Cheers

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#31
In reply to #24

### Re: POWER INVERTER SHUT DOWN

09/20/2012 4:46 AM

Laa Lucke,

It is true,a Westpoint Refrigerator.I agree with your thought that this compressor was added later.Because the specs are totally confusing regarding the true situation.

The specs for compressor seen are :f=50/60Hz,Voltage( V)=220-240V,Power= 1hp

I will connect it to the main grid and measure the starting and running quntities.

But from other comments of our fellows,say that the modified sine wave inverter can not operate such a device even if the size of it is correct,can you comment on this sir?

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#33
In reply to #31

### Re: POWER INVERTER SHUT DOWN

09/20/2012 7:55 AM

Thobias,

First thing first: Do the Trials to get the correct amps drawn by the compressor so that you could decide if the inverter is adequate.

Even if the output is a modified sine wave, it will be able to drive a motor if the size is small enough not to surge too high when started.

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#17
In reply to #13

### Re: POWER INVERTER SHUT DOWN

09/18/2012 1:46 PM
• "But what does it mean when the fridge manufacturer prints that the cross input power is 80W? while the compressor itself is rated as 1Hp,that's 750W!"

As mentioned, something is dreadfully wrong in these two values, and I would venture to say that it is the 1HP value. 80W is approx. 1/10th HP, which you may be mis-reading when it says .1HP and would be relatively consistent with a small 206 liter energy efficient refrigerator from what I have seen.

So then why would this little 80W compressor motor cause your 1200W surge capacity inverter to shut down? I'd venture to say the inverter values are grossly inflated, it is MUCH more common in that industry. Those little ref. compressors have a "kick start" accessory in them, which is an over sized capacitor to give in more starting torque because it is a closed head system. The charging current of the capacitor is causing your cheap inverter to shutdown because it cannot differentiate a 1 cycle capacitor charging inrush current spike from a real surge.

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#29
In reply to #17

### Re: POWER INVERTER SHUT DOWN

09/19/2012 9:11 AM

Thanks for your comment sir,but why do you say a "cheap inverter"?, I bought it last year for US\$ 125,is it cheap?(modified sine wave type),pls give from your exper.how it could cost.

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#32
In reply to #1

### Re: POWER INVERTER SHUT DOWN

09/20/2012 4:56 AM

Dear SM,

Thanks for your comment,Other fellows say that for this device to operate(all inductive loads for this manner) need only pure sine wave inverter,pls can you comment on this?

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#34
In reply to #32

### Re: POWER INVERTER SHUT DOWN

09/22/2012 10:34 AM

In most cases an appropriately sized, modified sine inverter can be used on an AC motors like the one of a fridge (with a bit lower efficiency and torque and some extra noise, if you want the small print) S.M.

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#35
In reply to #34

### Re: POWER INVERTER SHUT DOWN

09/24/2012 4:26 AM

SM,

Thank you.

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#2

### Re: Power Inverter Shut Down

09/17/2012 5:59 PM

Your solar power is available only during the day. Your battery has only 2400 W hour which means, for example, it can deliver only 24 W for 100 hours, 240 W for 10 hours during night. This is what is available to you. Forget for the moment the specs. of your inverter. Your fridge starting power demand can hit 600 W or more for a few seconds. You have also other loads connected to the inverter. Please disconnect all other load, keep only one light load connected. Then try out your fridge when you have max. out put from solar panel. This, I believe, will work out. Let us see the result. Wait for 24 hours more, to get some more views/feedback from other members of the forum. By the way, how old are the batteries?

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#3

### Re: Power Inverter Shut Down

09/17/2012 6:51 PM

This should work with a pure sine wave inverter...

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#4

### Re: Power Inverter Shut Down

09/17/2012 11:00 PM

your refrigerator needs alot more amperage when the compressor is starting than it would need while it's running.

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#6

### Re: Power Inverter Shut Down

09/17/2012 11:29 PM

600 W is way too small of an inverter. I ran my house with a 2500 watt steady state, 5000 watt peak inverter, and separate 1200 watt inverter for the computer system. I had a standard electric refrigerator, which was the biggest electrical load. Using a toaster or electric coffee pot was not feasible, but I found ways around those problems.

Your 12 volt battery bank is 12 volts when no current is being drawn. A load with a motor, such as refrigerator, will draw enough current to drag a small battery bank below the low voltage shutdown for the inverter. The inverter will trip off, the battery voltage will come back up with no load on it, and you'll be wondering why it shut off. Inverters are designed to shut down at under-voltage or over-voltage. I experienced the same problem. Again, the solution is more battery capacity. Again, if finances are tight, I would recommend you go to a place that sells reconditioned fork lift batteries. The one I got for 500 dollars weighed 1500 pounds, was as good as new (12.8 volts after sitting idle for a month with no charger connected at all during that time period) and cost me 500 dollars. I considered it a real bargain. 200 AH isn't squat for an off the grid system. You need a LOT more.

These suggestions are not meant to contradict the above answers, merely supplement

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#7

### Re: Power Inverter Shut Down

09/18/2012 1:31 AM

Is it a true sin wave or modified sin wave invertor?

Does the invertor turn off immediately when the fridge tries to start or after a period of continuous running ?

What are your ambient conditions? How's the airflow on the invertor (steady and unrestricted)?

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#21
In reply to #7

### Re: Power Inverter Shut Down

09/19/2012 7:00 AM

It's modified sinewave,it switches off immediately.

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#26
In reply to #21

### Re: Power Inverter Shut Down

09/19/2012 7:48 AM

Modified sin wave (MSW). You may be stuffed then.

I had an experience with a small pump motor whose plated requirements were well under the MSW invertor's rating that would not spin up and just growled.....many years ago. No big deal that time as it wasn't a requirement just something I tried. (note to self then was, from now on use TrueSW invertors only)

The fridge was 12Vdc if I remember correctly so there was no avenue for disappointment there.

The harmonics of MSW outputs is the snag.

The issue of running and starting motors with MSW invertors is discussed on the internet if you care to Google it for yourself.

There's still a question about the plated specs of your fridge. Measure the fridge current using a known "good" source if you can.

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#8

### Re: Power Inverter Shut Down

09/18/2012 4:56 AM

In summary, for this refrigerator and all the other loads hung onto them, the inverter and the solar eqipment upstream of them are both undersized.

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#9
In reply to #8

### Re: Power Inverter Shut Down

09/18/2012 5:37 AM

The invertor has a big question mark hanging over it for sure ( OP needs to start answering some questions), the panels and batteries are fine.

6hrs of sun per day x 300W = 1.8kWh of harvested energy daily.

12V x 200Ah = 2.4kWh of energy storage.

He only needs 0.81kWh of energy per day for his fridge (apparently) and can endure a bit over 2 days at a hit without good insolation once the batteries are fully charged.

It is possible to run out of juice at night if he has a series of poor insolation events without pause to recharge fully, but that plagues any battery storage system regardless of prime source. Not really a show stopper.

OP's only problem here is the invertor.

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#11
In reply to #9

### Re: Power Inverter Shut Down

09/18/2012 6:34 AM

The problem arises when the fridge kick starts. OP has not answered to the age of battery query yet. One cell with high internal resistance will bring the entire battery bank to it's knees. One can not use all the power of the battery - 2,400 W.

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#12
In reply to #11

### Re: Power Inverter Shut Down

09/18/2012 7:31 AM

The problem arises when the fridge kick starts. The OP needs to confirm this but it does seem highly probable that this is the case here.

If one (or more) batteries was as compromised as this then there would be other problems and probably not intermittent. Even if the batteries did do this then the solar panels have enough power alone for running (maybe not starting) the fridge through the invertor if the sun is shining.

Op doesn't need 2400W for running. Starting may need 400W if the start load is 5x, if it's 10x then the invertor will bog down.

That battery would have a 2 hr power rating of 1200W. Plenty. 200Ah is (usually) the C2 rating.

What is the start current for a small 80W fridge I wonder?

OP, plug your fridge into the utility supply and see what it actually pulls on start. Stop everybody guessing.

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#22
In reply to #11

### Re: Power Inverter Shut Down

09/19/2012 7:08 AM

The batteries are new ,the time taken since installed is about 6months.This was done(switched ON the fridge) while other loads were off.

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#10
In reply to #8

### Re: Power Inverter Shut Down

09/18/2012 6:09 AM

Correction - go with #9↑.

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#15

### Re: Power Inverter Shut Down

09/18/2012 10:26 AM

The motors in general have a start(run) current up to rated current in many times. may be ten times .as number #1 said .and your inverter has a protection of the overcurrent when the load current(start current) exceeds the overcurrent value automatically your inve switches off.

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#16

### Re: Power Inverter Shut Down

09/18/2012 11:12 AM

That's it then. Your invertor is too small.

I didn't tweak at the tiny power rating you quoted for your fridge

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#36

### Re: Power Inverter Shut Down

12/10/2012 11:58 AM

would large capacitors provide the starting current needed?