Saturday, February 16, 2013

Compatibility issue between MS2000 inverter and Splendide 2100XC Washer/Dryer


In January we installed the new Magnum MS2000 inverter, replacing the failed ProSine 2000.   You can read more about all that here: http://mvvikingstar.blogspot.com/2013/01/a-peek-inside-magnum.html .  All had been well, until we did a test run  of the our Splendide Washer/Dryer running on the inverter - and it failed.  And if you want to get your propeller hat a spinning, read on.  If not, just know I have found some special case where there is a problem and still need to give the parties involved a chance to resolve it.  This post is just talking about what is failing...

OK, if you are reading on - here goes:  About 1/3 of the way into the wash cycle the Splendide starts moving the wash back and forth, mixing things up I guess.  And when on the Inverter it really goes nuts - lights flash, and the washer motion becomes jerky.  Clearly things are not happy.

Searching the internet found an obscure reference to a 'Known issue' between the Magnum inverter and Splendide washers.  An Email to the support department of both did get a quick response,  with each pointing the finger to the other :-)  (More on that to come I am hoping).

Always the inquisitive, I wanted to try to understand a bit better what was happening, so I broke out the Tek 222 O'Scope and started taking some 'pictures'   And here are some pictures of those pictures.  Sorry, I have not yet gotten the O'Scope connected to the Computer to directly download images, so we are doing it Old School - with a Camera.  (Ok, maybe not Old Old School - I am using a Digital Camera, not a Polaroid).


Here is the waveform of shore power, what a good True Sinewave inverter should emulate:

A 'Pure' Sinewave


Now TO BE FAIR - I have seen lots of waveforms from the Magnum that look what is above.  So lets not get the idea that this post is about an overall problem with the Magnum.   I am thinking it is really a case of when all the stars align that things go wrong.   And here is a picture of when things go wrong:

Failing Combination
Notice that kind of Hook circled in red?  What I believe I am seeing here is a problem with how the Magnum handles reactive loads, namely the inductive load of the washer / dryer drum motor.  That hook is when the machine fails.




Here is another picture, notice we still see the same flat-spot, but no hook?  Here the washer/dryer carries on:

This one seemed to work OK.


And here you can see the two images overlayed:

The Good and the Bad!


OK, so what is this all about?   Well, it appears to me there is a limitation in the Magnum inverter with inductive loads. Inductive loads are a special type of load known to cause Reactive Power to be drawn (as opposed to Real Power).  It is a major issue for shore-based power companies to deal with.  The problems, causes, and solutions are all well know.  But the application of this all is rather a dark art.  You can learn more here if you wish: http://en.wikipedia.org/wiki/AC_power#Real.2C_reactive.2C_and_apparent_powers

Back to Viking Star.  When looking at  how the Magnum handles other inductive loads (refrigerator, drill motor, drill press, vacuum)  the waveform shows a little distortion, but nothing dramatic -  and more important, no hooking.  So I am wondering what is special about the Splendide in the load it draws.  Maybe because the washer motor is on/off so much?   Maybe there is one too many corners cut in the Splendide power supply design? .  Another idea:  All the other inductive loads I tried were much larger overall then the Splendide - perhaps the problem is only when a rather light inductive load is placed on the Magnum.  Who knows, but all of this info I am sending to Magnum to see what insight / suggestions they have.


How to move forward, as we do need our washer/dryer working (and always using Shore Power is not an option!): 
  • Overwhelm the Reactive Power with a much larger Real Power load.   Turning on a Space Heater to Low does this (tested and confirmed).  But it also uses a LOT of  power.  A 100 or 60w light bulb might do the same, need to experiment.
  • Use a different inverter:  We know the Prosine works just fine - as long as it works at all.  It is reported that several 'cheap Chinese Sine-wave' inverters will also.  (This would be a sad situation where the Prosine and Chinese ones best the US Magnum...)
  • Splendide to make their washer less susceptible to waveform distortions.
  • Magnum to research this and improve their design (or perhaps I have a failed unit??)   Will see what happens next week.
  • Add Capacitance to the load to counteract the washer's inductive load and reduce the waveform distortions.
A light bulb might work (can one still buy 40 or 60w bulbs these days??), but again it is wasteful of energy.  The last point holds the most promise.   I will try to secure a motor Run Capacitor - the key here is getting just the right value and that might need experimenting.   A more advanced version is using a 'synchronous condenser', in effect an inductor motor (no, really) driving no load.  This CAN be more energy efficient than just a light bulb or heater, and has the advantage of in effect looking like a self-adjusting run capacitor.  I tried experiments this morning using the unloaded motor on a drill press and a vacuum  - both worked great. (In fact, the 3rd photo above is the 'failing' waveform de-hooked by the unloaded drill-press motor.)   A try with a small box fan that I pulled the blades off of did not work - just too small to have any real impact.

There is a 'Treasure Shop' on the Island here, and will be picking up a car Monday.  I will go there and see if I can find a small motor and/or some run capacitors to try.  I think in the end this will be the real answer.

Will post the conclusion of this invention when get more info.  Till then:  Wow:  Boats and Systems.  SO much more than the house!

.

2 comments:

  1. Interesting to see the Magnasine's "pure" sinewave so distorted. I _just_ ordered the MS2812 to install in my RV, after much debate over the far cheaper Chinese models.

    A few months have gone by since you posted this, have you made any progress, or received support from Magnum?

    Whenever my unit gets here (back ordered) I'll have to hook it up to my scope under various loads and see what the waveform looks like.

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    Replies
    1. Gordon,

      So sorry about not replying sooner - just lost track of things. In the end, Magnum only give their comment that the run-cap might help (and in our case it did), but was also very clear it was 'Not Their Problem'... Nothing more was coming from them. Another cruiser with a MS2012 tried my Run Cap solution and it did not work for him. He does not have any scope equipment, so we can not tell why. He is in the process of upgrading to a MS2812 and will be reporting on his results later this fall.

      On that: There are several 'It Works Great' and 'Wow, I have problem' comments floating around the net when using these small washer/dryer combo units. But VERY FEW come with specifics - in particular which model of the Magnum inverter is involved. To date I have a hand full of detailed 1st person reports from people, and the score is:

      FAiLED: 3x, all using MS2012 or MS2000 inverter (same 2,000w inverter, just one has an extra CB already installed)
      OK: 2x, using MS2812
      OK: 3x, using even larger Magnum inverters
      - but also using separate washer and dryer, not really the same situation.

      So, I think this 'issue' might be restricted to the small 2,000w Magnum Pure Sine inverters. We have noticed other potential issues with it (though I have not investigated it deeply), specifically:
      1) It will not start out 1/2HP air compressor (insufficient surge capacity), though the Prosine 2KW did fine and the 'surge' ratings of the 1/2Hp motor is under the 'surge' ratings of the MS2000 inverter.
      2) There is a noticeable 120v voltage drop every time our small AC powered refrigerator starts up. Enough to cause the Laptop computers to 'beep' as they switch from AC power to batteries, and then back again.

      My suspicious is: the 2,000w inverters are just designed with too much cost taken out of them, and are unable to properly support surges at startup. The Washer/Dryer really pointed this out, I was disappointed by the inability to power our air compressor, but am most suspicious of the drop that triggers our laptops when the refrigerator starts...

      And I suspect the 2800w and larger inverters do not have this deficiency....

      Maybe one day will scope the MS2000 and the Refrigerator, and compare it to the Magnum spec sheet. THAT should be interesting!

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