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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: energy in UK
Date: Thu, 17 Apr 2025 16:57:50 -0700
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On 4/17/25 1:50 PM, Carlos E.R. wrote:
> On 2025-04-17 21:05, KevinJ93 wrote:
>> On 4/17/25 2:28 AM, Don Y wrote:
>>> On 4/16/2025 6:55 PM, KevinJ93 wrote:
>>>> On 4/16/25 3:49 PM, Don Y wrote:
>>>>  > On 4/16/2025 3:11 AM, Martin Brown wrote:
>>>> <...>
>>>>  > Here, the issue is the high PEAK demands that the ACbrrs place on
>>>>  > individual
>>>>  > subscribers.  We could probably get by on a 3-5KW plant -- but, 
>>>> only if
>>>>  > we could store and deliver for large loads (I think the ACbrr is 
>>>> ~14KW).
>>>>
>>>> That's a very large residential A/C. Our 4-Ton unit (48kBTU/Hr) 
>>>> takes about 5kW and suffices a 2,900 sq ft house in northern 
>>>> California. (Don't you like all these antiquated units!)
>>>
>>> That's the startup load.  An inverter for a (pure) solar solution would
>>> have to tolerate that for some large fraction of a second/seconds.  
>>> I.e.,
>>> you would NEED to be grid-tied in order to support such large loads,
>>> even temporarily.
>>>
>>
>> 14kW startup is about 60A LRA (locked Rotor Amperage). A single Tesla 
>> Powerwall 3 battery is rated for 185A LRA and it is very common to 
>> have two or more Powerwalls in a system which increases the available 
>> short term power. Our A/C has a 104A LRA spec.
> 
> What would happen if the inverter on the battery pack doesn't have that 
> peak capacity?

The inverter would trip and power would be cutoff until reset.

> I mean, an inverter might simply limit the maximum peak current without 
> destroying itself, keeping itself all the time within safe limits. Would 
> the motor still start, albeit slowly? Or would it stall and overheat? 
> Perhaps motors could be designed co cope. I know my AC unit has an 
> inverter inside to control the motor, so does my fridge.
> 
> ...