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Old 10-06-2010, 13:52   #31
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Originally Posted by Daedalusk View Post
I had previously done this voltage test myself, but discounted the reading as false. He says it is not false, but indicated ac leakage into the dc system from within the Freedom 30.
Interesting, an ac leakage of what current magnitude?
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Old 10-06-2010, 17:44   #32
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"occurring at a 120 Hz rate." That would seem to be a magic number, i.e. twice the 60Hz frequency of mains power in the US. But from the scope tracing it looks like the pulses are spaced every 40ms (4 large units, each five x 2ms units on the display?) which would be a rate of 25Hz not 120Hz, if I've done my math right?

"Is there a mathematician in the house?" <G>

No, really....120Hz?? or my math??
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Old 10-06-2010, 18:14   #33
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Its 2 milliseconds per vertical grid line, so about 8.4 ms per pulse which is 120 Hz. Which would go along with some kind of full wave rectification of the 60 Hz AC input. As far as the magnitude of the available current behind the spike, I would say it is very large given the small impact that large capacitor has on it. I'm sure there is some calculation that would give a numerical answer, but I don't have it.

We've already spent $500 on getting the thing repaired. Its unfortunate that I didn't do this before it failed so I could insist the repair facility ensure that ripple was within specifications. At this point I'm not sure its worth taking it out and shipping it back for what would probably be an expensive evaluation by the shop, and possibly a BS line about how it was all normal. I think the ultimate solution is a more modern unit when it fails again.

Chip
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Old 10-06-2018, 09:03   #34
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Re: Noisy Freedom Inverter / Charger

All,

The only way out of this kind of problem is to create a clean power supply powering only the equipment that is sensitive to DC noise. Modified sine wave inverters are noisy beasts that can drive some electronic equipment nuts.

Here is how to create a clean supply (for a 12V system). Everything you need will be easily available on Ebay. Be sure everything below is protected and fused because these large capacitors pack a wallop and can melt stuff if you short out the terminals or the downstream wiring is not fused.

1. Add up the amp ratings of the electronic devices you wish to run.

2. Get a bridge diode with an amp rating a good bit higher than the amp rating of the devices you wish to run. What you will be doing is to run house DC through it to fully rectify the house DC into a new circuit to power your stuff. Get a bridge diode with a hole in the middle that you can screw to something. It will have 4 leads. You connect the input 12V to the two opposing leads marked with ~ (squiggles). The output comes off the other two leads and will be marked + and -.

3. Get one or more huge capacitors about 70,000 MFD rated for 35VDC and mounting bracket(s). These caps will be slightly over 3" dia and 4" high. for 24V systems you want to get caps rated for at least 48VDC.

4. Wire the capacitors across the output of the bridge diode, connecting + side of capacitor to DC + side.


5. Wire an ATC or ATO fuse holder with correct size fuse slightly lower than the amp rating of the bridge diode.

6. You might need to add a fuse barrier strip to separately fuse different items you will be connecting.

7. You want to build this into a project box with a metal backplate. Mount this box in a cooler location in your boat so the capacitors do not overheat. there are various fiberglass and also waterproof boxes you can get. Do not use cheap plastic boxes.

8. Run wiring from your "clean" power supply to your devices. Be sure to not ground the minus side of the DC output to chassis ground of your rig or the noise will come back.

NOTE: This power supply will be about 1 volt less than your dirty DC voltage (due to voltage drop across the bridge diode). If your house voltage is 13.8v, your clean supply will be about 12.8v (not enough to charge batteries). When disconnected from shore power and alternator not running you will be at 11vdc or less as battery power drops. Be sure your equipment can run on that voltage. Do not try to run an inverter of this, it won't work, most inverters shut down at 10.5 vdc
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Old 10-06-2018, 11:21   #35
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Re: Noisy Freedom Inverter / Charger

Since the need was for 30 amps of 14 volt power, this is not practical. Wow. 10 years ago....
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Old 10-06-2018, 12:05   #36
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Re: Noisy Freedom Inverter / Charger

I posted it because I was wondering why I have the same problem on a Heart inverter in my Monaco RV with a piece of audio equipment. It took a few days of probing undocumented RV wiring to figure it out.

The posting might be old but people find these threads for contemporary problems.
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