Voltage drop to 150v for 220v 1200btu mobil air cooler while trying run via 1500w pure sine inverter

[hk5528]

Hello,
I have a setup of 1.5KW 220v pure sine inverter with 3Kw peak, and 400Ah lifepo battery, which I have tested with heat gun and run for 20-30 mins at 1.4-1.5KW w/o any issue. while I have just tried to run mobil air cooler 220v 12000btu with max power consumption is around 1.2KW I have encountered an issue. When I used with grid have no issue and max power consumption that I have seen on the meter is around 1.2KW for a/c.
Problem is happening with inverter. When the a/c compressor starts voltage drops to 150v which causes even more amp consumption. What I have thought is to if I can apply a soft starter SSR to solve this problem, may be something similar to, because I m not sure if I upgrade the inverter to 2 or 3kw pure sine would solve the problem or not? thanks in advance for reading and advices.

https://www.aliexpress.us/item/2255...662890175!sea!US!0&curPageLogUid=wkepzVJJUEZt

 

[waross]

Starting A/C on limited sources:
I have a lot of experience starting A/C sets on standby generators.
The rule of thumb i that the spare or available capacity of the generator should be three times the A/C rating.
Less than that and the voltage drop and the frequency drop seen by other loads are excessive.
An absolute minimum ratio is 2 1/2 times tha A/C rating.
At 2 1/2 times, the voltage will probably drop to about 150 Volts, but the frequency will also drop to about 40 Hz which greatly aids motor starting.
This is a feature of the Automatic Voltage Regulator called Under Frequency Roll Off (UFRO).
You won't have UFRO that with an inverter.
But the soft start is not that expensive and may work.
You are peaking at two times the A/C capacity.
Running a remote sawmill on diesel power, we were able to start large motors, about 200 Hp, with a soft start.
I can say definitely that it may work and it may not work.
Like the carney said at the circus game of chance;
"You pay your money and you take your chance."

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[hk5528]

Thanks for the reply waross,

I have only checked the AC voltage dropped to 150v from 220v, not checked frequency tbh. Which I will also check the possible frequency drop asap. But AC volt and possible frequency drop is causing in rush current as 65AMP peak, and 3kw is the exact 2 and 1/2 times of 1.2kw of mobil a/c based on your calc, probably I need something around 3kw sine inverter, may be even 24v DC instead of 12V DC.

 

[waross]

The frequency drop of a generator is because the heavy load slows down the prime mover.
I doubt that your inverter changes frequency due to load.
The point is that that is an advantage that the generator has over the inverter.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LittleInch]

Is everyone here ignoring power factor of these small motors? Whenever I've looked more closely at invertor / battery pack their headline "rating" is at a PF of 1 - i.e. reactive loads like a kettle or heater. The power able to be supplied to a motor drops to about 60% or less of the headline power rating.

Also I've never quite worked out how they rate these max normal and then "peak" outputs for invertors.

Unless you can take your a/c machine apart and insert the soft starter before the compressor then I'm really not sure it is going to work.

But your whole system is running far too close to the margins. a 12V line is running at over 250A at 3kW so you will have extra losses appearing all over the place.

Simple motor compressor starts are probably peaking short term at 5-6 times running current. Your invertor just doesn't have enough in it to provide that peak supply.

Bigger invertor.

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