MPP LV5048 weird activity

TKB4

Solar Enthusiast
Joined
Dec 2, 2019
Messages
208
I currently have 2 MPP LV5048 s in parallel. I have a 5 ton 2 stage scroll compressor HVAC unit that I only use in stage 1 which is about 3 1/2 ton equivalent. I know the single MPP wont start it so I obtained 2 more to use in parallel . I have only connected one more at this point . I read inrush for HVAC at close to 100 amps so I ordered and installed a hyper engineering soft start kit and the inrush dropped to 24 amps and it runs in cooling mode on about 11.3 amps in stage 1. I then connected the HVAC unit to it and it and the 2 parallel units do start it and run it.

The problem is it isnt running as smoothly as on grid power and when its running the lcd readouts on the LV5048 s show continually changing outputs both watts amps and battery voltages etc. The AC out wires form the individual units also shoe much higher current than the 11.3 amps it runs on from grid power. Checking main battery cables its is drawing more than expected amps to generate the 11.3 amps at 240v .

This makes me think the hyper engineering soft start is either trying to change the phase angle continuously or maybe creating some radio wave type interference that is affecting the LV5048 s. Either way I am not powering the HVAC with it till I get something figured out. If it was just during startup I would think its just "dirty" power due to THD s at near the inverters limits etc but it continues while running too. I also thought if that had something to do with it I would try paralleling the third unit and see if higher potential amps would help. Maybe somehow its using most of the power from just 1 LV5048 and adding some from 2nd causing master to be closer to max? Any settings to adjust other than just paralleling? I currently have 60 Kwhr of Li Ion batteries connected also as well as 12,300 PV watts connected. It makes no difference whether day or night either.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,779
After the first 300-500 msecs for startup the hyper engineering soft starter is not involved. Did you allow it to do its training startups on grid power first? A/C compressor fan should not go through soft starter.

Sounds like a problem with the inverters with some kind of unstable operation. Might be battery cabling voltage drop. Also might be the inverters don't like the A/C power factor. High freq inverters don't take poor power factor as well as low freq inverters. There is actually reverse current flow during portion of AC waveform cycle with inductive power factor that can cause instability in the inverter's high freq DC to HV DC converter.

Do you have your battery cables taped together in parallel. This reduces their series inductance which can create oscillations and more stress on inverter.

There is a way to improve A/C power factor but you need to measure what it is first. Likely in range of 0.85.
You can try putting a 40-50 uF run capacitor on compressor side of relay contactor, but before softstarter, to see if it improves situation. Don't leave it as without knowing actual requirement for PF correction it can create problems with over correction at certain operational conditions. For permanent install you will also need a surge limiting thermistor in series with PF correcting capacitor to avoid too much stress on relay contactor contacts.

Power Factor AC meter 1.jpg
 
Last edited:

syclonedriver

Solar Enthusiast
Joined
May 16, 2021
Messages
78
Another test would be to place a resistive load on the inverter after the compressor starts. Something like a space heater or some large incandescent bulbs. Probably have to use 2 space heaters in series to make it work with 240v. If this reduces the issue its probably power factor related.

I wonder if a ground loop would cause this behavior?
 

TKB4

Solar Enthusiast
Joined
Dec 2, 2019
Messages
208
I currently have 2 sets of 20 Kwhr of 56 modules of Nissan Leaf cells connected to 2 parallel LV5048 s there are two 2 gauge welding cables connecting to each of these terminals
Then the 2 paralleled LV5048 s are also connected with same type cables to the same terminals . So 4 negative cables and 4 positive cables to each terminal with one pair from each battery bank and one pair from each LV5048

I could try with just one battery bank connected to see if that helps.
After the first 300-500 msecs for startup the hyper engineering soft starter is not involved. Did you allow it to do its training startups on grid power first? A/C compressor fan should not go through soft starter.

Sounds like a problem with the inverters with some kind of unstable operation. Might be battery cabling voltage drop. Also might be the inverters don't like the A/C power factor. High freq inverters don't take poor power factor as well as low freq inverters. There is actually reverse current flow during portion of AC waveform cycle with inductive power factor that can cause instability in the inverter's high freq DC to HV DC converter.

Do you have your battery cables taped together in parallel. This reduces their series inductance which can create oscillations and more stress on inverter.

There is a way to improve A/C power factor but you need to measure what it is first. Likely in range of 0.85.
You can try putting a 40-50 uF run capacitor on compressor side of relay contactor, but before softstarter, to see if it improves situation. Don't leave it as without knowing actual requirement for PF correction it can create problems with over correction at certain operational conditions. For permanent install you will also need a surge limiting thermistor in series with PF correcting capacitor to avoid too much stress on relay contactor contacts.

View attachment 63348
Yes I have used the soft start for months prior to trying the HVAC with the inverters. The compressor fan is inverter type and is all in one package unit so it is being powered by the same source. The battery cable lengths are 8 feet total ( 4 feet on each side of the terminals ) This behavior also occurred when PV input was over 7,000 watts and will even show charging batteries at times while the behavior is occurring. See my other pos also
 
Top