Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Inverter size for running fridge?
#21
>....A typical fridge in North America is single phase.
Yes - 120v
Reply
#22
Actually, half phase. Single phase would be full 240V, electric dryer/water-heater/etc.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#23
If an inverter is used, a 3 phase motor can be run from a "single" phase supply eg 120VAC

AFAIK 120V AC (1x live, 1x neutral) is still called "single phase". Isn't typical US 240V AC (2x live) called split-phase?
https://en.wikipedia.org/wiki/Split-phas...tric_power
Running off solar, DIY & electronics fan :-)
Reply
#24
As per the wiki link posted, a single wire from the power lines (1 phase-wire) goes to a transformer and 3 wires comes out. This equates to two hot wires (240V) and a split voltage of a 120V between a hot and tap. Each split is 180* out of phase with the other. This means that 240VAC is split in half and produce a split-phase circuit.
In the US, there are usually only 3 hot wires running down the lines. Each line represents a phase as power is generated using 3-phase. The 4th wire on the power line is a ground wire.

However, we're getting away from OP now.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#25
The motor is likely 3 phase if it's driven from a variable speed drive (inverter). The controller is a single phase to 3-pahse inverter.

As per what is detailed in :

Go into google and enter "W10710090 filetype:pdf" (inverter replacement part no)
Click on the "VARIABLE CAPACITY COMPRESSOR EELECTRONIC" pdf link (embraco inverter - not exact part match)
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Reply
#26
Okay, so, let's see if I have have wrapped my head around this.  The compressor might still need more amps than what the LRA has stated because it may be referring to what is supplied to it by the inverter, while the amp's that need to be supplied to the inverter may add up to more?  I tried looking around for some more specs on the inverter and found this label from one being sold on Ebay.  Does this move us closer to a definitive answer?  And thanks again, I am learning so much!

Reply
#27
As it seems available info is limited, our best guess is like mentioned earlier: allow for approx 2-3 times normal running amps for the start-up. It might only be 1.5 times.

With inverters, the units without large iron core transformers typically have much more limited real surge ability.
Units with the heavy transformers typically have much better genuine surge ratings.
So when purchasing, the weight of a unit will help figure out likely real world surge abilities.
Running off solar, DIY & electronics fan :-)
Reply
#28
Long answer....

The ratings on the label would seem to indicate the "AVERAGE" input should be limited to 3.3A max.

The output is 3 phase with varying PWM to create an effective voltage upto 230V (voltage doubler) with a varying frequency between 47Hz and 133Hz.

The 230V output is significant because what this is saying is that half of the cycle one set of capacitors are charged and then the other half cycle a separate set are charged. Taking the -ve 120V half cycle and using that to charge one capacitor(set) and then the +ve half cycle to charge up a separate set. The two capacitors are then in series to give you the effective 230V ouptut capability.

What this means for an inverter is that all of the "AVERAGE" rms current is actually delivered in a short spike towards the top of the voltage waveform. This is the effect / way that a lot of switch mode power supplies work by charging the capacitors at the top of the waveform.

With UPS units (inverters) they quote a value called "crest factor" because they predominantly supply computer power supplies which are almost always AC-->DC-->Capacity-->Switching-->DC out.

The crest factor is how many multiples rating (peak surge) the inverter can cope with under normal use and is typically around 2.5-3.0. i.e. a 1kW UPS at 120V (8.3A) would be able to supply regular sustained current spikes of 20.8A but not for more than the 1KW rms effective power.

Very few powerwall inverters have this figure. The rating is effectively a proxy as to the peak current handling capability of the switching FET's and the rest of the design.

So....long answer short.... a typical 1kW inverter should work fine but if your inverter is a basic cheap design if you were to plug in 4.5A worth of computer type loads (crest factor>2) then it may well blow the inverter even though the average load is below 1kW.

Very short.... 1kW yes, don't load it up to anywhere near 1kW with other loads.

If it's not actually an inverter driven compressor your 1kW inverter may likely pop.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Reply
#29
Inverter wise there is a key choice.   High-frequency inverters don't have surge capability whereas low-frequency inverters (with heavy transformers) typically do.      The surge capability allows for motor surge.     They both might be rated for 1000w but without surge it will fail right above 1000w instantly whereas one with surge will have some seconds where it can handle 2x or 3x overload produced by a traditional motor starting up.
Reply
#30
A oil filled 100mfd - 50mfd motor run capacitor would handle the surge and inverter will not see the big power spike.

Mount it in a sealed metal box with a 20 amp circuit breaker to prevent capacitor failure problems  ( possible fire )
Turn the inverter on first, second the capacitor , third the fridge.

For reference
https://www.ebay.com/itm/100-uF-370-V-44...Sw8Opa8jzG

https://www.ebay.com/itm/KVAR-Energy-Sav...SwRgJXgb50

Jim jr
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)