Marine DC to AC Inverter Instant Overcurrent Start SURGE Limitation - CHECK THE DETAILS - TRY BEFORE BUYING?

Subject: T&T: <mfg deleted> inverter, one more comment

I would like to add one comment to the discussion on the <mfg deleted> inverter.

I have the <mfg deleted> MS2812, "rated" 2800 watts AC continuous at 60 Hz.  3900 watts 5 seconds rating.

I selected a dingy davit with 110 VAC power (1 HP).  Normally operate from the genset, I wanted to be able to power from the inverter in case of a failure with the genset.

I assumed that the inverter power would be more than adequate for a 1 HP motor.  1 HP = 746 watts, but a single phase low horsepower motor is rather inefficient, I would guess around 1000 watts running.

The inverter will not power the davit.  Not a phase angle issue, or a sine wave issue; it is the locked rotor current that the inverter sees for milliseconds (ms) at startup.  When I investigated, the locked rotor current on a 1 HP motor exceed 80 amps.  Nearly 10 KW!

If you read the fine print in the <mfg deleted> spec, the MS2812 is "rated" 70 amp surge for 1 ms; 40 amp surge for 100 ms.

My inverter control panel showed a fault message, I think it was "AC overload", and shuts down the inverter.

>From my manual, I note that the MS2012 is rated 50 amps for 1 ms, 33 amps for 100 ms.

So, you may not be seeing an issue with "pure" sine wave or not; and you may not be seeing a phase angle issue.  You may be overloading the inverter due to the start current of the motor in your washer.

Apparently, the design of the <mfg deleted> inverter allows for less "instant" overcurrent than some other manufacturers with a similar "continuous" rating.

If you could find some way to "borrow" a MS2812 and try operating with that unit, it might solve your problem.

On the other hand, the MS4024 (28 VDC input) is rated 120 amps for 1 ms, 84 amps for 100 ms; thus shoud be able to start and run a 1 HP motor.  Does not do me anygood, unless I wanted to convert the boat to 28 volts--not in the present plan.

Overall, I like the <mfg deleted>, and would (and have) recommend it.  Appears to be well built, and is repairable, unlike some other inverters.

It does have one other design feature that I don't like:  If for some reason, your charge cycle gets interrupted, you have to wait until the battery voltage drops below 12.6 volts before the charger will re-start a full charge cycle (bulk charge).  According to their tech support, no way to bypass and force a charge cycle, you must wait until the battery voltage drops.  When at anchor and doing a daily recharge from the genset, I have run into this problem a couple of times.

Chet

BOTTOM LINE - CHECK THE INVERTER SPECS CLOSELY - IF POSSIBLE TRY IT WITH THE ACTUAL DEVICES YOU INTEND TO USE IT WITH BEFORE YOU BUY IT.... lol