Is there any way to time delay to revert to AC mode in the the Kodak OG 7.2 KVA. Problem is there are surges and power drops as mains power is resumed after a period of load shedding. Is there a way to delay the AC draw so as only to revert to that mode once the power has stabilized?

 

3 hours ago, DGH said:

Is there any way to time delay to revert to AC mode in the the Kodak OG 7.2 KVA. Problem is there are surges and power drops as mains power is resumed after a period of load shedding. Is there a way to delay the AC draw so as only to revert to that mode once the power has stabilized?

 

Hi DGH, when the OG7. 2 is in battery mode while grid is not available, the grid is internally disconnected  by the grid/safety relay, both live and neutral. 

When the grid becomes available again, the relay does not energize immediately. The machine first monitors the grid for being within limits, then it synhronize the inverter itself to this grid, then only it operates the relay and ties the grid ti the inverter and loads. 

The parts exposed before the relay is typically surge protection. 

So i dont think you need to delay the grid for the machine's sake, unless there appears some obscenely  high voltages, in which case it might hurt the surge protectors themselves. 

 

Edited July 22, 20233 yr by BritishRacingGreen

I had a symilar problem, but even a 32 min delay would not solve my problem.

I was really under the impression that my Inverter - with enough battery backup (10kW), is the best solution to bad power inputs and to protect all appliances (fridges, computers etc. downstream with clean stabelised pure sine wave power within it's specs.

It was late night and my system was setup as SUB, and in Batt-mode at that stage because of the "load shedding".

The switch back to Line-mode after Loadshedding was a mess, and Inverter settled in Line-mode, but giving me between 90 and 110V on the Output side to my home. Only my 4W LED lights remained on. When the TV switced off, I rushed outside and switched Eskom OFF, and forcing it back to Battery-mode.

I understand that the inverter (because of the low power input settings of 90 - 280V)  was allowed to switch back to line mode, but the least I expected was that:

1) The inverter should either stay in battery mode where it had enough power to supply to the house.

2) or, simbly blend in some battery power to conform with the output specs of the Kodak OG-7.2 (specified output voltage of 230V +- 5%).  

Do I maybe miss something?

Spending all this money and still have the same risk of damaging electronics, fridges etc doesn't make sense.

If this inverter really can't supply clean power reliabilly up to spec (or rather nothing at all if in trouble), then what else will do the job.

Any suggestions would be appreciated.

Regards,

Gerhard 

31 minutes ago, GPvdB said:

I had a symilar problem, but even a 32 min delay would not solve my problem.

I was really under the impression that my Inverter - with enough battery backup (10kW), is the best solution to bad power inputs and to protect all appliances (fridges, computers etc. downstream with clean stabelised pure sine wave power within it's specs.

It was late night and my system was setup as SUB, and in Batt-mode at that stage because of the "load shedding".

The switch back to Line-mode after Loadshedding was a mess, and Inverter settled in Line-mode, but giving me between 90 and 110V on the Output side to my home. Only my 4W LED lights remained on. When the TV switced off, I rushed outside and switched Eskom OFF, and forcing it back to Battery-mode.

I understand that the inverter (because of the low power input settings of 90 - 280V)  was allowed to switch back to line mode, but the least I expected was that:

1) The inverter should either stay in battery mode where it had enough power to supply to the house.

2) or, simbly blend in some battery power to conform with the output specs of the Kodak OG-7.2 (specified output voltage of 230V +- 5%).  

Do I maybe miss something?

Spending all this money and still have the same risk of damaging electronics, fridges etc doesn't make sense.

If this inverter really can't supply clean power reliabilly up to spec (or rather nothing at all if in trouble), then what else will do the job.

Any suggestions would be appreciated.

Regards,

Gerhard 

I feel your pain, but yourOG7. 2, and most other makes and models are not designed to cleanup the grid, except for some special machines thats actually designed for that purpose. And the ONLY one I know of is the Axpert KING, which converts the grid to dc, and then reconstruct it to AC. 

Interesting - thanks.

Marketing brocures tends to tell only the nice side of a product, knowing that not everybody has the knowledge or experience to ask the right questions in advance, only to then discover the bad part of the product by accident when it is to late. 

To me as a retired mechanical engineer I was always under the impression that a pure sine wave inverter was disigned to provide clean on spec power to protect computers and sensitive equipment against bad power. But the loophole is certanly that it must run only from batteries and not have direct Eskom input as an option?

Sad but true! 

2 hours ago, GPvdB said:

Interesting - thanks.

Marketing brocures tends to tell only the nice side of a product, knowing that not everybody has the knowledge or experience to ask the right questions in advance, only to then discover the bad part of the product by accident when it is to late. 

To me as a retired mechanical engineer I was always under the impression that a pure sine wave inverter was disigned to provide clean on spec power to protect computers and sensitive equipment against bad power. But the loophole is certanly that it must run only from batteries and not have direct Eskom input as an option?

Sad but true! 

It seems you are spot on but I a small way these are termed as off grid inverters. 

Thanks @BritishRacingGreen I for one thought that all the high voltage MPPT Voltronic type that can blend do it by taking AC and converting to DC and then filter the output back to AC. It just shows you how wrong can one be. 

2 hours ago, Scorp007 said:

It seems you are spot on but I a small way these are termed as off grid inverters. 

Thanks @BritishRacingGreen I for one thought that all the high voltage MPPT Voltronic type that can blend do it by taking AC and converting to DC and then filter the output back to AC. It just shows you how wrong can one be. 

Yes, even the high pv voltage machines are gridtied internally, so even when they blend dc sources to to the grid, thats 'pushed' against the grid, but the grid content remains raw and distorted. 

When one comes to think about it, the raw grid has a very low impedance, and its very difficult and expensive to smooth the rough edges with filtering. It would have been great if one could add a 50hz notch filter, which would restore the original pure 50hz, but imagine the size of such a beast.

Even surge protection means nothing if there is not a downstream  fuse or breaker to trip when its clamped, otherwise it will melt if it tries to arrest the entire grid source. 

 

Edited July 23, 20233 yr by BritishRacingGreen

1 hour ago, BritishRacingGreen said:

Yes, even the high pv voltage machines are gridtied internally, so even when they blend dc sources to to the grid, thats 'pushed' against the grid, but the grid content remains raw and distorted. 

When one comes to think about it, the raw grid has a very low impedance, and its very difficult and expensive to smooth the rough edges with filtering. It would have been great if one could add a 50hz notch filter, which would restore the original pure 50hz, but imagine the size of such a beast.

Even surge protection means nothing if there is not a downstream  fuse or breaker to trip when its clamped, otherwise it will melt if it tries to arrest the entire grid source. 

 

Thanks as always. 

Does your inverter have UPS/APL setting ? You could try to change to UPS, as it accepts a narrower range of input voltages and transfer time will be shorter when grid voltage is stable (which probably won't happen after load shedding anyways, but still...).

 

Yes, that was my first change I made - Setting 03 to UPS (input 170 -280V).

I just woner why they didn't give me a choise to set it to what I want.

I am now investigating devices that switch off bad mains within your own setting range and return grid power only after it is back within your setting limits. 
So cheap it should be part of the inverter?

R 375 (TakeAlot)

Description

Specification

Rated voltage :220V

Operation voltage range: AC80V~400V(Single Phase)

Rated frequency:50Hz

Rate current:1A-63A adjustable

Under-voltge action cut-off value: 140V-210V

Over-voltage action cut-off value: 230V-300V

Uand

Range of time delay: 1s-600s

Voltage measurement accuracy:1%(Not exceeding 1% of the overall range)

Rated insulation voltage: 400V

Output contact: 1NO

Protection degree: IP20

Or another one:

 

 

According to me these under/over voltage cutout switches will have the same reaction time as the inverter internal voltage cutout switches, so it wont improve the powers quality, or in other words, there will still be milliseconds long high voltage spikes the entire time you are connected to the grid, especially when they turn on and off other parts of the grid for load shedding .

The cheapest way to filter these surges is to install fast responding surge protection in all the db's with plug top surge protectors for all the sensitive devises.