Author Topic: How bad would it be to run a 70W Sodium setup off modified square wave inverter  (Read 1318 times)
HomeBrewLamps
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How bad would it be to run a 70W Sodium setup off modified square wave inverter « on: September 23, 2018, 02:55:23 AM » Author: HomeBrewLamps
I am wanting to to this but I'm curious as to how harmful this is to the inverter.... I don't care about the gear as much as I do the inverter itself.. If the gear developes a bit of heat that's fine because it will be air cooled for sure.. I was thinking of using my 70 choke gear..
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funkybulb
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Re: How bad would it be to run a 70W Sodium setup off modified square wave inverter « Reply #1 on: September 23, 2018, 09:01:06 AM » Author: funkybulb
I have ran 70 watt cooper MH on a Vector 1200 watt inverter.  problem was it killed ignitor after a month of service.  I had return the light back to store got a refund
other than that running preheat fluorescent to electronic
ballast. even ran 400 watt mercury vapor on it.
 
make sure you run small incandescent load on it
with inductive loads
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Medved
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Re: How bad would it be to run a 70W Sodium setup off modified square wave inverter « Reply #2 on: September 23, 2018, 09:36:39 AM » Author: Medved
In any case make sure there isn't any PFC capacitor connected paralle to the ballast input or its primary winding (in case of a PF corrected HX autotransformer ballast). If the sodium ballast has a PFC capacitor on its input, the inverter is heavily suffering from high current spikes. These may overheat the transformer and/or transistors. Usually the inverters having the switching transistors on the secondary side will refuse to drive it and shut off (they will detect it as a short circuit, which the capacitor on a rectangular shaped voltage essentially is; the designs using inverter chopper on the primary and then the transformer will dissipate this short circuit energy in the transformer, overheating it).

Then it depends, if the inverter design really counts with inductive loading.
You should keep in mind the current phase lag translates into rather high AC current component on the DC side of the inverter chopper.
If it is a type having an inverter on the low voltage side and then the trasformer, you will see high 100/120Hz saw-tooth shape AC current in the battery input, loading the battery. But what is most important here, the steep current edge causes rather voltage spikes across any inductance between the battery and the inverter. So you have to make sure these connections are short and do not form large loop. Problems are mainly with buses, where the battery is in the rear close to the engine (many bigger RV's are build on some originally bus platform, so keep that in mind), just the +24V wire going to the "ignition switch" is already way too long (there you should mount the inverter in the rear, switched via a relay or a remote power switch input).
If it is the type where first the battery voltage is converted to 170/324V (for a 120/230V AC) and then using a transistor bridge making the MSW AC out of that, the reverse current (part of the sawtooth) has nowhere to go except when there is sufficiently large capacitor on the 170/324V DC bus. Not all inverters have that, there are many that have there just small film capacitors (HF filtering for the step up DCDC), don't forget the "IT equipment" does not cause any phase shift, so many inverters sold as "for phone chargers/notebooks" may just be lacking such capacitor.
And even if the capacitor is there, it has to be sufficiently rated. Generally you have to look, how much reactive power the inverter allows. If there is no such rating, there is rather "high chance" it has no tank capacitor at all so it will fail rather soon.
So your possibilities are:
Either choose an inverter sufficiently reactive rated (a 70W HPS requires at least 200VAr tolerance; it is about the same VAr's for both "120V world", as well as "230V world" lamps and their ballasts; you are looking for long term rating) by its maker,
or reverse engineer the inverter circuit and determine
- What system is the inverter
- If it has sufficient capacitor on the DC bus (at least 200uF for a 230V/50Hz unit, 350uF for 120V/60Hz unit), include the ripple current rating (you have to find its datasheet; 1Arms/100Hz for the 230V, 1.8Arms for the 120V).
- If it does not feature that capacitor, you may add it to the circuit (you have to determine the power DC bus connections; he rating see above)
- If it is the system using the low frequency transformer and you can not connect it close to the battery, you may substitute the close battery connection by a sufficiently large electrolytic capacitor (40mF/20Arms for a 12V input device, 20mF/10Arms for a 24V device; "mF" i really a milifarad according to the standard so pretty large bank, not as many ignorants tend to label "microfarads")
Of course, multiple capacitors in parallel means their capacitances, as well as ripple current rating sums up (so you may use 20 pieces of "2200uF/35V" in parallel for the 12V unit mentioned above; you will very unlikely find a reasonable priced single unit for the total rating, the common practice is using a bank of smaller units, e.g. 20 units in parallel are nothing uncommon in power electronic).
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HomeBrewLamps
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Re: How bad would it be to run a 70W Sodium setup off modified square wave inverter « Reply #3 on: October 03, 2018, 08:46:40 PM » Author: HomeBrewLamps
Thankyou.... I've decided that I will save the inverter for another project and buy a proper sine wave inverter....
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:colorbulb: Scavenger, Urban Explorer, Lighting Enthusiast and Creator of homebrewlamps 8) :colorbulb:

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Re: How bad would it be to run a 70W Sodium setup off modified square wave inverter « Reply #4 on: October 06, 2018, 10:25:07 PM » Author: HomeBrewLamps
I actually have a new question... What if I obtained a 70 watt HPS electronic ballast? Would that be able to function properly on a modified sine wave inverter?
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Re: How bad would it be to run a 70W Sodium setup off modified square wave inverter « Reply #5 on: October 07, 2018, 03:32:13 AM » Author: Medved
I actually have a new question... What if I obtained a 70 watt HPS electronic ballast? Would that be able to function properly on a modified sine wave inverter?

The electronic is the same type of load as the computers most of the inverters are designed for, so in the theory it shoul work.
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