[RE-wrenches] 1/2 wave loads

Sat Dec 21 15:41:42 PST 2024

Way to complicated.  The “half wave load” is as described earlier.  It is a cheap way to get a hair drier (or other heater) with a three-way switch to have air, half power and full power.  The half power routes the hot side through a diode so that the heating element only get half power.  Full power is no diode.  This can cause trouble with some inverters, and I am sure is a terrible (noisy) load on any AC line, but it is cheap and they don’t care about the side affects. 

David

> On Dec 21, 2024, at 2:05 PM, pieter offgridenterprises.org via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
> 
> Nomenclature! After all of this discussion it sounds like “half wave load” is being used to describe a load that is only using one of the two 120 volt legs a standard 120/240 split phase inverter provides. That being the case the AC output current rating should be looked at. For example an inverter rated at 9KW might have a 37.5 amp max output current rating. That means the inverter is only rated to supply 37.5 amps per leg. So in other words 120VAC X 37.5 amps =4500 Watts, (at unity power factor) or 240AC X 37.5 amps =9000Watts (at unity power factor). If a load is connected on one of the two 120 volt line to Neutral legs and the current exceeds 37.5amps the load will exceed the inverter rating. If the power factor is not 1, then the output watts can be less than the output VA.. It is possible that what is being referred to as a “half wave load”  could more accurately be described as an unbalanced load. That being the case the total load on the inverter may be less than the specified load rating, but the load current on one “leg” maybe more than the inverter rated output current. If the leg currents are measured and found not be reasonably balanced it may be possible to correct the issue by re arranging circuit breakers in the MDP.
> Pieter Huebner
> Project Manager
> Off Grid Enterprises
>  
>  
> From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org <mailto:re-wrenches-bounces at lists.re-wrenches.org>> On Behalf Of Jay via RE-wrenches
> Sent: Saturday, December 21, 2024 10:55 AM
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>>
> Cc: Jay <jay.peltz at gmail.com <mailto:jay.peltz at gmail.com>>
> Subject: Re: [RE-wrenches] 1/2 wave loads
>  
> I can’t remember if I sent the update.
>  
> We identified the load as a Japanese bidet. Once unplugged everything is working normally. 
>  
> So whatever people want to call the 1/2 wave. It’s what multiple OEMS call it. 
>  
> If I can find an oscilloscope I’ll send along what the wave form looks like. 
>  
> Jay
>  
>  
> 
> 
> On Dec 19, 2024, at 10:11 AM, Jesse Dahl via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> 
> I think about resistive loads as “in-phase”. Half-wave seem like they would a load with a diode blocking one side of the waveform. 
> Sent from my iPhone
> 
> 
> On Dec 18, 2024, at 3:03 PM, Jay via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> 
> 
> I will add that I’ve heard privately off list that it’s actually smaller loads that seem to be the issue. 
>  
> And larger 1500 watt electric heaters seem to work ok. 
>  
> I’m wondering if anyone else has come across this issue and I guess more importantly is there a fix?  
>  
> Jay
> 
> 
> On Dec 18, 2024, at 1:52 PM, Jay <jay.peltz at gmail.com <mailto:jay.peltz at gmail.com>> wrote:
> 
> 
> Here is what I understand 1/2 wave loads to be. 
>  
> As I understand it, Heater loads are the main issue. 
>  
> Toasters, toaster ovens, hair dryers, aquarium/terraium heaters etc. 
>  
> But if there are other things pls let us know 
>  
> Jay
> 
> 
> On Dec 18, 2024, at 1:34 PM, GLBCC via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> 
> 
> What is a half wave load?
>  
> On Dec 18, 2024 13:35, Jay via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> Hi all. 
> 
> I’ve recently been made aware that the fortress inverter isn’t too happy with 1/2 wave loads.
> 
> I’m wondering if this is an issue with the AIO or solark?
> 
> Thanks in advance 
> 
> Jay
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