Fieldlines.com || square/sine/modified sine

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products

square/sine/modified sine
By Budgreen, Section Homebrewed Electricity Posted on Tue Jan 27, 2004 at 11:59:01 AM MST
best guess?

hello all.
I have a perplexing question to ask. is it possible to tell the output from an inverter without a scope? reason I ask is that I have acquired an older (1989) 800W ups unit, it is an alpha-800 power source and runs from 36v. I will be adding this into my basement system mainly because it has a functioning charger and if I can keep 36v of my batteries charged thats great. but the main problem I have is trying to figure out what waveform it uses and without a scope i'm at a loss! best I can tell is the output stage is using bipolar transistors going into a large transformer and I would imagine it could have a sinewave drive but not sure without tearing it to bits to trace out the board. also the manual is no help, just says not to run highly capacitive or inductive loads because it won't handle the surge.

square/sine/modified sine | 5 comments (5 topical)

Re: square/sine/modified sine (none / 0) (#1)
by RobD on Tue Jan 27, 2004 at 01:05:36 PM MST

Hi Bud, Yes, You can do it with an AC meter that is not true rms the voltage will show 20 to 30 volts lower if it is mod sine. Compare it to the reading from your standard outlet. RobD

Re: square/sine/modified sine (none / 0) (#2)
by Victor on Tue Jan 27, 2004 at 01:27:49 PM MST

Hi Bud;
I suspect a square wave. This would read about 11% high with a non rms meter. If your meter can capture 1ms peaks, the square wave should be approx 120 v, sine or mod.sine should be about 160 volts.

You might rectify the output and charge a lightly loaded capacitor , 1 k.ohm or so ,to deturmine the peak voltage. I'm trying to say that the resistor would be in parallel with the cap to bleed off noise spikes.

Victor

Re: square/sine/modified sine (none / 0) (#3)
by RobD on Tue Jan 27, 2004 at 09:12:17 PM MST

Bud and 5KW,
I just did an interesting experiment. I took a plain Jane new inverter and put a scope, a standard meter and a super RMS meter on the output.
Here's what I got. The scope showed 140 volts peak voltage with a 6 ms high and 10.6 ms off (approx). The HP true RMS bench meter read 116.12 volts and the Fluke standard meter read 110.3 volts.
Some of the old inverters were 50% duty cycle and like 5KW said yours might be this type, I remember seeing some of the old Best inverters that ran SCRs and big transformers being like this. If that's the case you might very well see slightly higher voltage than the 115 most inverters are set at. It's a hard call but you might try taking a digital thermometer and measuring the heat of a running motor through the inverter and than through the house AC line. If the motor runs hotter through the inverter it's probably a square wave. It is possible if it was a commercial unit that they ran it pure sine. You can check the drive devices and get back with the numbers, this might be a clue.
RobD

Re: square/sine/modified sine (none / 0) (#4)
by Jerry on Tue Jan 27, 2004 at 10:00:37 PM MST

Hi Rod D
Is use a 2500 watt mod/sin at work on my stores RE system.

I've notice that 2 pole and 4 pole AC induction motors run on this wave form but 6 pole and 8 pole AC induction motors just grolw and maybe turn at 1 rpm.

The 2 ands 4 pole run ok but they are noisyer than on grid power.

JK TAS Jerry

Airheads Page

[ Parent ]

Re: square/sine/modified sine (none / 0) (#5)
by Budgreen on Thu Jan 29, 2004 at 01:21:16 PM MST

it uses 2 large bipolar transistors to drive the xfmr. it was a backup for a phone system and dsl router untill the last blackout.

[ Parent ]

square/sine/modified sine | 5 comments (5 topical)

Menu

· create account
· How to use the board
· FAQs
· search the board
· Google search the board

Login

Make a new account

Username:

Password:

Total Views

85 Scoop users have viewed this posting.

Related Links

· Also by Budgreen

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest © 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!