Trace MSW ??'s

shokman

I have read links on hear about MSW vs PSW, I have an old Trace 2012 inverter that came with cabin purchase 10 years ago. Cabin is in a small collection of off grid cabins/homes. I have been encourage to upgrade to 24V system with new inverter. However there are several systems here with modern $2k + PSW inverters that have had their share of issues and having been told by person who sells installs, them to not expect much more than 10yrs service. I have spent $'s originally on heavy wire to minimise 12v line losses and been using "the tank" which is probably 30+ yrs old with no apparent issues. Yes AM radio is noisy and digital clocks are about as time concious as I am. Using an older flat screen TV for several years now with no apparent problem. My question is, want to purchase a new smart TV and wondering if it would be affected by MSW.
Marc

706jim

I doubt that the TV would be affected by MSW current. I have a fairly new TV and it runs just fine off my old Trace DR1524. I spoke recently with the designer of this unit complimenting him on its reliability. I've used it since 1994 and it still works great. Yours is even older but seems to be doing great. I think the newer high frequency inverters aren't nearly as tolerant of overloads or surges.

BB.

It does not always "work"... But you can use a Kill-a-Watt type meter and measure the power factor your your loads--Especially those loads running on your MSW inverter.

https://en.wikipedia.org/wiki/Power_factor

Many modern AC power supplies used on computers and such are "power factor corrected". Those type of power supplies are usually pretty tolerant of running on MSW waveforms. I would suggest that devices with PF >0.90 should be work well. Those with PF <0.80 are at a risk of running hot/failing on MSW inverters.

Power Factor is basically the ratio of current used to run the device vs total current used by the device. A PF=1.0 is "perfect" and all AC current used by the device is used to power the device. A PF=0.50 means 1/2 the current powers the device and the other 1/2 is "wasted"...

AC power math is actually quite complex... But a couple of pretty easy to understand examples.

Imagine you are pulling a car down the road with a rope. And you want a 100 lb pull to move the car forward. If you stand in front of the car and pull, 100% (PF=1.0) of the force you use to pull goes into moving the car forward.

Now, stand 60 degrees off to the side of the car... Cosine 60 degrees = 0.5 (PF=0.5) or 1/2 the force goes into pulling the car forward, the other 1/2 pulls the car sideways--But because of the wheels, the car does not move sideways. If you need 100 lbs of force to move the car forward, then you need to pull on the rope with 200 lbs of force to do that--And the rope needs to be 2x stronger.

Similar... Say you "jerk" on the rope... Pull at 400 lbs for 1 second and rest for 3 seconds. The rope needs to be 4x stronger (rated for 400 lbs) to put an average of 100 lbs of force on the car to move it forward.

MSW is (more or less) a square wave with sharp "edges" as the voltage goes from zero to XXX volts back to zero volts. Those "sharp edges" can cause issues with various electrical devices (transformers, induction motors, older AC power supply inputs, etc.). And those issues usually involved "wasted heat" in the components and devices.

There are lots of equations for power:
Power = Voltage * Current
Power = Voltage^2 / R
Power = Current^2 * R

The thing to notice is heating goes with the square of the voltage of current through the device. If you double the current, the self heating goes up by a factor of 4x... So if you have a PF of 0.5 which means an average of 2x more AC current flow, the resistance of the wire/devices/diodes/etc. get 4x more waste heat.

With induction motors--They turn their RPM based on the line frequency of 50 or 60 Hz... MSW wave forms have a base frequency of 50/60 Hz, but MSW also has higher frequencies (Harmonics) too (those higher frequencies are because of the "sharp edges"). That current still goes into the motors--But does no "useful" work (turning the shaft). So instead those "circulating" currents generate waste heat. About 20% of the energy in an MSW inverter's output is >60 Hz.

Older/simpler AC power supplies frequently use a Diode(s) connected to a capacitor(s) to change AC to DC voltage/current. This "clips" the current from the peak of the wave form (sine wave peaks, or the "sharp edge" of MSW inverter output voltage). Which means that diode/capacitor set can overheat bay taking "too much" current on those sharp voltage edges.

Anyway, Usually devices with "good power factor" (>0.90 or so) work OK on MSW inverters. And those with poor PF run hot and/or eventually fail. It was the old 80/20 rule... 80% of the stuff works "OK", and 10-20% does not--And you cannot tell by looking the device to know (you can sometimes get "buzzing" in devices from MSW input--But that is not always bad--Just sometimes a distraction).

Refrigerator compressors run near rated power all the time (more heat in motor, they run hot and can fail)... A power saw runs for a few seconds at power (cutting wood), then is not used (repositioning wood or turned off). "Cheap/small" power supplies tend to run hot ("power bricks" in cords, transformers hanging on wall outlets). Better/newer supplies tend to be power factor corrected (last few decades, more laws requiring PFC for devices to "save energy").

This website does a very nice job of explaining AC power and generators/inverters as used for Movie Equipment.. Sinewave and MSW issues are also discussed:

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

-Bill

Photowhit

I'm pretty much ignorant of how an LED TV works, perhaps Bill can fill in the gaps, but I think they, in essence, work on DC for the tuner and then back to AC for the screen. Somewhat like a laptop. I think some even have external 'warts' to converter Ac to DC. This will usually bode well for a square or stepped wave inverter. I think many/most are built with this internally.

I also suspect that there might be an inverter to the actual screen. I've burned up an inverter for a laptop computer screen before, but like I said it's not my end of the pool. I did replace the inverter and only used the laptop with the battery installed. I think that added a buffer, but I was living on a tiny solar array nearly 20 years ago and didn't want to leave the laptop charging when I turned it off. Today, my Lenovo automatically quits charging to prolong battery life. If they knew it might help people living on solar they'd make it an add-on and charge double...lol

Here's a power supply for a 32" Samsung LED TV;



https://www.amazon.com/UN32J4500-UN32J4500AF-UN32J4500AFXZA-BN44-00837A-A4819-FDY/dp/B07RGJCS26/ref=sr_1_3

shokman

Thanks guys! I think I’ll take my chances with new tv and sound bar but now wondering if PF will be on tv or in accompanying literature lol

BB.

PF... Almost zero chance of being listed.

Strangely, have seen quite a few twisty florescent bulbs that listed 0.55 PF or so.

Many of the electronic supplies and equipment that list 110-240 VAC are power factor corrected (good thing). Will run in 110 thru 240 VAC).

Supplies that list a single voltage (120 VAC or 240 VAC) or list 120/240 (auto or manual voltage select between the two voltages) are not power factor corrected.

Bill

littleharbor2

My neighbor here in Baja has an old Trace U2512 MSW inverter. It has served him well over the last 25 years or so. He has Directtv and a large LED TV He has tried everything to get his tv to put out an HD picture. It occurred to me that his inverter's square wave output might have something to do with the problem.  He's gone thru every setting on the tv and hd receiver and fine tuned his dish to no avail. 

Thoughts?

BB.

What is happening with the TV? Is it not receiving over the air HD/Digital signals? Not better than 480i from DirecTV?

Does he have a genset he can try (turn off the MSW inverter and run the TV+Sat receiver from genset)?

-Bill

Dave Angelini

There was a reason even 25 + years ago that people who lived offgrid, wanted sine wave electronics.

littleharbor2

BB. said:

What is happening with the TV? Is it not receiving over the air HD/Digital signals? Not better than 480i from DirecTV?

Does he have a genset he can try (turn off the MSW inverter and run the TV+Sat receiver from genset)?

-Bill

The guide channel has a small hi def icon on each channel that is coming through as hi-def. He has not a single icon.

I'll run the generator option by him. Don't think he has tried that. His generator has only been used as a direct hook up to his 220 volt air conditioning unit.

BB.

Has your friend called Directv and see if their account has HD, and he has an HD Capable receiver (older receivers may not?)?

In times past, one could also send a re-authorization request too and make sure that the proper profile is loaded/authorized....

Is he pointed at the correct satellites and getting the correct channels/signal strength expected for the content desired?

I don't know anything about Sat-TV--... Just some things that a quick search brought up.

-Bill

littleharbor2

 Bill, Yes to all the above.