Home  |  Contents 
Electronics
  Forum Index : Electronics         Section
Subject Topic: 8 KW Inverter Build Post ReplyPost New Topic
<< Prev Page of 16
Author
Message << Prev Topic | Next Topic >>
oztules
Guru
Guru
Avatar

Joined: 26 July 2007
Location: Australia
Online Status: Offline
Posts: 1341
Posted: 08 January 2017 at 9:44am | IP Logged Quote oztules

Mad,
Further testing with the inductor gives me a huge range of weird stuff.

It looks like the noise in my transformer is induced by the inductor.
By changing the inductor form iron powder to ferrite, from ecore to ring and changing the turns.. the noise and waveform imperfections changed radically.

On one setting with the ring and 10 turns the tranny was so quite I had to put my ear next to it to see if it was running. With a different ring and 10 turns, the wave from looked like your trace at idle, and sounded like a chaff cutter at idle, but straightened up a lot when loaded.

So it looks like that with removing the 4u7 and fiddling with the inductor, we can change the waveform markedly. It may be I am on the edge of decency with regards to drive, but gee, it gets very good by fiddling the inductor, and removing the 4u7 on the VFB line.

more to follow as I find out more.... gee it would be nice if I knew what I was doing too


...........oztules

Edited by oztules on 08 January 2017 at 9:46am


__________________
Village idiot...or... just another hack out of his depth


Back to Top View oztules's Profile Search for other posts by oztules
 
Tinker
Guru
Guru
Avatar

Joined: 07 November 2007
Location: Australia
Online Status: Offline
Posts: 1077
Posted: 08 January 2017 at 10:53am | IP Logged Quote Tinker

Warpspeed wrote:


A better way is to use something like a TC4452 twelve amp non inverting driver chip and a 1.0 ohm series gate resistor mounted right up close to each mosfet. We are talking about driving some very large mosfets here, with maybe up to 10nF gate capacitance.

http://ww1.microchip.com/downloads/en/DeviceDoc/20001987C.pdf

Then parallel up all the TC4452 inputs, and drive that with your IR isolated gate driver.



Looking at that spec PDF in the link above I notice a diagram with one input and two outputs from that chip.
So, with using a EG8010, I assume one requires 4 of these chips to drive the Mosfets?
Then, what is one going to connect to the extra outputs from the TC4452.

Just curious and trying to learn new electronic tricks.


__________________
Klaus
Back to Top View Tinker's Profile Search for other posts by Tinker
 
Madness
Guru
Guru
Avatar

Joined: 08 October 2011
Location: Australia
Online Status: Offline
Posts: 636
Posted: 08 January 2017 at 10:59am | IP Logged Quote Madness

Thanks OZ and Warp,

The Aero-Sharp GTI could be sick, after all they were all recalled units. I have plenty of spare bits to play with. When it was working the watts it was supposedly making did not seem to match up with its daily total, ie it was making around 300 plus watts for 2.4 hours but total daily output was 0.2 KWH. One thing that was interesting is while it was connected it made the OGI 50% quieter, this happen as soon as the AC was connected and prior to it making any power. Another thing I noticed was the power meter I have in the OGI was showing a power factor of 0.6.


Interesting about the Inductor, the one I am using ATM came from Tinker which is 3.5 turns of 4 pieces of enamelled copper bar. It is definitely a major source of noise, sounds much better now as I have removed it from being bolted to the inverter case where it sounded like it was possessed. I have the 100 mm Ferrite ring that I have played around with 6 turns on it that seemed to work well and was quiet. I have been trying to wind it with multiple strands of 2mm wire but that gets real messy. I might go to a welding supply shop tomorrow and get some welding wire for it.



__________________
Off the grid and on the cloud
Back to Top View Madness's Profile Search for other posts by Madness
 
Warpspeed
Guru
Guru


Joined: 09 August 2007
Location: Australia
Online Status: Offline
Posts: 660
Posted: 08 January 2017 at 11:14am | IP Logged Quote Warpspeed

Klaus,

It has one input, and the usual internal N channel pull down mosfet, and internal P channel pull up mosfet.
In just about all CMOS chips the drains of the two complimentary output mosfets are tied together internally, to produce a rail to rail output swing on one output pin.

But in this chip, the two drains come out to two separate pins.
Those two pins can simply be joined together and used in the normal way.

Having two individual outputs (one pull down, the other pull up) enable you to use two separate gate drive resistors which can be made very different values. You can arrange it to have very different turn on and turn off switching speeds for your large power mosfet.

That is no real advantage in most circuits, but for things like current mode flyback and boost converters, it can be handy to have a fairly leasurly noise free turn on, and the fastest possible turn off. You might want to do that if you are monitoring source current with a shunt or current transformer.

You may not want to have a 12 amp gate drive pulse put a 12 amp turn on spike into your source mounted current shunt. So very limited gate drive current at turn on fixes that articular problem.

Edited by Warpspeed on 08 January 2017 at 11:16am


__________________
Cheers, Tony.
Back to Top View Warpspeed's Profile Search for other posts by Warpspeed
 
Tinker
Guru
Guru
Avatar

Joined: 07 November 2007
Location: Australia
Online Status: Offline
Posts: 1077
Posted: 08 January 2017 at 1:02pm | IP Logged Quote Tinker

Madness wrote:

Interesting about the Inductor, the one I am using ATM came from Tinker which is 3.5 turns of 4 pieces of enamelled copper bar. It is definitely a major source of noise, sounds much better now as I have removed it from being bolted to the inverter case where it sounded like it was possessed.


Did you locate the exact source of the noise?
I should think the enamelled copper bar is stiff enough to resist any vibrations.
The E core halves *must* be clamped very securely otherwise they definitely are noisy. I use 1mm neoprene rubber pieces under the top clamp to get an even pressure without stressing the ferrite.

Also, the 3 1/2 turns, whilst they are locked together with epoxy also should not move in any way on the core once the choke is assembled.
I did that on mine by epoxying dowel halves (cut like a D) to the inside of the coil turns since with such stiff copper bars there is no way to wrap them tight around the bobbin.

I will experiment more with my choke once more Mosfets arrive to do some testing.

I would say using insulated welding cable can make a tighter wrap as the many strands are much more flexible but its at the expense of a fair bit less copper cross section area.

Interestingly, on the chokes I removed from that 'well known Australian manufaturer's inverter they used many in hand of relatively thin wire to cover the ring evenly all way around in a single layer. The whole lot must have got rather hot by the burnt appearance. The ring cores - 4 stacked ones - were perhaps powdered iron, they did not look like ferrite. I tried them with several turns of multistrand wire but had noise issues and a higher idling current.

__________________
Klaus
Back to Top View Tinker's Profile Search for other posts by Tinker
 
Madness
Guru
Guru
Avatar

Joined: 08 October 2011
Location: Australia
Online Status: Offline
Posts: 636
Posted: 08 January 2017 at 1:31pm | IP Logged Quote Madness

Hi Tinker,

The inductor is all rock solid, It has wood pieces in each end and epoxied so there is no movement in it. The level of noise dropped by a very large factor by having it suspended by a couple cable ties rather than clamped to the Inverter case. So the noise did not come from something loose in the inductor.

I am going to use the welding wire on a Ferrite Ring 100X65X20, it could take wire up to 30MM diametre. Using this with a single core Toroid I could get idle current down to 0.26A with 6 turns on it. I will get 90MM square wire which will wrap around the ring very easily. Once I get this Inverter sorted out I am planning to build another and use 90 mm wire for the primary, the 70mm I have on it ATM has room to spare and the wire can be compressed to fit more turns around the in circumference if needed. The OD between 70 and 90 is only a few mm.

__________________
Off the grid and on the cloud
Back to Top View Madness's Profile Search for other posts by Madness
 
Tinker
Guru
Guru
Avatar

Joined: 07 November 2007
Location: Australia
Online Status: Offline
Posts: 1077
Posted: 09 January 2017 at 10:48am | IP Logged Quote Tinker

That's interesting madness, I assume there was magnetic coupling to the metal case that made the noise.
My E-core choke is bolted to a 12mm plywood base which in turn screws to the case. But so far the inverter did not run long enough under load to worry about noise from that part .

I just ordered a ferrite ring too, a little bigger (120x80x25) than yours and a little more expensive. This one has a fair number of buyers for some reason.
More room to wrap wire around too and another excuse for more experimenting.
I wonder what happens if there is a choke in each primary leg?

A new batch of HY4008's turned up today, all measured 3.0 mOhm and passed my 75VDC drain/source test. I did not push them to 80V as at 75V a tiny current (O.0000001A) started to flow which is as per spec sheet.

We'll see if I get that thing to behave as expected with these Mosfets.



__________________
Klaus
Back to Top View Tinker's Profile Search for other posts by Tinker
 
Madness
Guru
Guru
Avatar

Joined: 08 October 2011
Location: Australia
Online Status: Offline
Posts: 636
Posted: 09 January 2017 at 12:27pm | IP Logged Quote Madness

Hi Tinker,

I think the noise is a physical connection, plus the case is made of 2 Aero Sharp cases welded together so the part where they meet could be vibrating against each other making it worse.

Yes it's frustrating when you spend a heap of time on something and as soon as you power it up it sh@ts itself. The Hy4008w's I got tested the same 3 mOhm also but they behaved just the same as the 4110's which is wy I am now working on the drive side as they all work fine with 3 FETs on each leg but not 6.

I got some 95 mm welding wire today, that fits comfortably with 6 turns in the ring. But I have not had time to run it yet, I have Wednesday off so will get to it then.

In the EG8010 data sheet they show using two chokes for a bipolar setup rather than the unipolar setup we are using. If you have not done it have a look at either side of the choke with your CRO, there is some serious white mans magic happening those things.

__________________
Off the grid and on the cloud
Back to Top View Madness's Profile Search for other posts by Madness
 
oztules
Guru
Guru
Avatar

Joined: 26 July 2007
Location: Australia
Online Status: Offline
Posts: 1341
Posted: 10 January 2017 at 11:04am | IP Logged Quote oztules

Have not progressed too much further, the darn thing works too well.
With the 4u7 clipped off the VFB, and a small ring with 5 turns for the inductor, the thing ran 5kw and was virtually silent. 6 fets/leg 4011

No I don't know why, it is just perfect.
This is using the inspire boxes... the curves were a problem but not any more.




It is running over 5kw, very very quiet, and the temp seems much lower than I remembered before the small changes.

Will try to get more sens out of it/me tomorrow.

......oztules



__________________
Village idiot...or... just another hack out of his depth
Back to Top View oztules's Profile Search for other posts by oztules
 
Madness
Guru
Guru
Avatar

Joined: 08 October 2011
Location: Australia
Online Status: Offline
Posts: 636
Posted: 10 January 2017 at 11:29am | IP Logged Quote Madness

Hi Oz,

I have time tomorrow to do some more fiddling also, so off with the 4u7, I gave my new Ferrite ring choke a quick run but it was like a stair case on leading side of the wave. Suspect the 95 mm wire I used is not wound tight enough, so I will see if I can get it tighter, if not I will put cable ties on it to pull the wire on the inside of the ring out against the ferrite.

Also I have a board ready to try with speed up caps across the gate resistors to see if they have any positive effect.

Another job is to swap the main PCB in the Aero Sharp and see if it play more nicely.

__________________
Off the grid and on the cloud
Back to Top View Madness's Profile Search for other posts by Madness
 
oztules
Guru
Guru
Avatar

Joined: 26 July 2007
Location: Australia
Online Status: Offline
Posts: 1341
Posted: 10 January 2017 at 12:34pm | IP Logged Quote oztules

So, you have found the inductor makes a big change too. I suspect the transformer may too ( only small I think), will test tomorrow or next.

This unit was bit noisy compared to others I have built, ran very well, and kicked 20kw, but a bit noisy with a glitch shown before.

As the glitch changed shape and size, the noise changed appreciably.

Now, very quiet, except for heat gun and freezer. Like I said seems cooler for the same loads by about 10C... not sure if it's the weather or the 4u7 and inductor combo... or something else, but cooler is betterer.

All units out in the field have had no failures, and some have been out there for near a year, with no interference from me. Every one seems to now own jugs, pie makers, microwaves and electric hot water services, NBN satellite modems ( constant 50 watts 24/7 ) and toasters etc...... and they don't seem to be afraid to use em.

One of the island ones will soon have an extra 1.5kw all day for the desalination unit out there..... all very civilized.

Hopefully that picture above will help those using inspires... the curves are not a problem.... just chop them off, and join like the aerosharp boxes.


..........oztules

Edited by oztules on 10 January 2017 at 12:36pm


__________________
Village idiot...or... just another hack out of his depth
Back to Top View oztules's Profile Search for other posts by oztules
 
Madness
Guru
Guru
Avatar

Joined: 08 October 2011
Location: Australia
Online Status: Offline
Posts: 636
Posted: 10 January 2017 at 8:59pm | IP Logged Quote Madness

oztules wrote:






Hi Oz,

This photo shows one definite difference between your boards and mine. Those long legs, the board I have that is working the best is TO220 4110 FETs with legs about 12 mm long. All the rest are TO247 and they are in the board as far as they can go which leaves only 5 mm of exposed leg above the PCB. All these boards work fine with 3 FETs on each leg but with a full house they have sharp spikes in the waveform.

__________________
Off the grid and on the cloud
Back to Top View Madness's Profile Search for other posts by Madness
 


If you wish to post a reply to this topic you must first login
If you are not already registered you must first register

  Search the forums using Google.
<< Prev Page of 16
In the news...
 
Post ReplyPost New Topic
Printable version Printable version
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Powered by Web Wiz Forums version 7.8
Copyright ©2001-2004 Web Wiz Guide

This page was generated in 0.0762 seconds.
Privacy Policy     Process times : 0, 0, 0, 0.08