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Old 20th April 2017, 11:45 AM   #361
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Default Transformation

Woop - the post arrived today with 2x transformers for the Q-Watt project. Should give 41V AC off load, and 39V AC @ 420 VA.

Thanks Delange, Kay.

Pops.
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Old 20th April 2017, 08:32 PM   #362
calpe is offline calpe  Gibraltar
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Popchops, just to mention in the Elektor Q-Watt article they state: -
2 x 40v, 500VA.
Their example was a Nuvotem Talema Tx as listed in RS Components, code 223-8285, 69.

What is the VA of the Canterbury Tx, just out of curiosity?
I'm sure the Canterbury quality will do its job.
Keep us posted
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Old 20th April 2017, 09:08 PM   #363
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Bingo. Tranny is bang on target. My mains is normally really close to 240V and I'm getting 55-56V DC.

Each transformer is built on a 500VA core but wound with more copper & lower flux density. Terry rates them at 420VA. Regulation is 'better than 5%'.

Pops.
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Last edited by popchops; 20th April 2017 at 09:16 PM.
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Old 20th April 2017, 09:55 PM   #364
calpe is offline calpe  Gibraltar
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Hey popchops, that great news!
And measured with your Fluke too!
Keep us posted...
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Old 20th April 2017, 10:29 PM   #365
calpe is offline calpe  Gibraltar
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popchops, if you haven't done it, it'll be a good idea to check this out, taken from the Q-Watt article: -

Mount the plate to IC1 with enough distance from the PCB so it won’t come in contact with R1, R5 and R4.
Bend L1 a little (away) from the heat sink.
Important: the metal part of the backside of IC1 is connected to the negative supply voltage.
If only a thermal compound is used between heat sink and IC there is a big chance the heat sink is also connected to the negative supply voltage,
.

Because of this i placed a piece of thermal insulator pad inbetween IC1 and its heatsink, so that the metal part on rear side of IC1 was completely covered, and therefore the high possibility of the heatsink being at -55v was removed.
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Old 21st April 2017, 08:51 AM   #366
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Hi Calpe,

did you increase the heat sink area accordingly?

Best regards!
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Old 21st April 2017, 05:38 PM   #367
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Quote:
Originally Posted by calpe View Post
Popchops, just to mention in the Elektor Q-Watt article they state: -
2 x 40v, 500VA.
Their example was a Nuvotem Talema Tx as listed in RS Components, code 223-8285
These are wound for 230V primary so 40V version is closer to 42V with 240V input.

And the 40V rating is at full load so actually you would get 45V AC at idle in the UK. You really want 41V AC at idle.

Last edited by popchops; 21st April 2017 at 05:49 PM.
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Old 21st April 2017, 09:07 PM   #368
calpe is offline calpe  Gibraltar
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One Q-Watt (dual channel) up and working!
No issues at all of stability nor oscillation in any shape or form!

My life and my Q-Watt project were in my hands when i begun this project, I'm still alive and my Q-Watt is working fantastic!

Ive used the same case as fellow constructor popchops. A really good quality case.
The same Switched Mode Power Supplies SMPS500R's (S.M.P.S.) as fellow constructor delange. Quality products!

As popchops, i too am using the same case 3U 300mm deep case from hifi2000
https://www.modushop.biz/site/index....ory&path=66_96

Take heed of Elektors write up about the setting up of the Q-Watt (i.e. 47R resistors etc.).

After the initial switch on (with working multimeter) the Quiescent current very comfortable settles down and was then adjusted to its 30mA. The Q-Watt was left on for 15/20 minutes and the Q.Current remained at 30mA.

Having run the Q-Watt for 15/20 minutes at quite a high volume, the heatsinks of the 3U case remained quite cool.

For those interested, attached is the PDF of the LME49811, that explains its 'onboard' protections. I used an insulator inbetween the IC and the heatsink, thus removing the -55v on its heatsink.

In post #26 there is information of the thermal characteristics of the 3U case.

Post #35 explains about a better pot to adjust the Q.Current, i have these fitted.

Post #48 is an explanation for those using a S.M.P.S. so that the Q-Watt relay is switched on. Designed by 'delange', I too used this Cct.

Post #101 (and #104/146) delange explains the use of an input level pot, which i found to be an excellent idea and i too have implemented it.

I preferred to use M3 nylon standoffs for the PCB's and SMPS's.

Finally, i repeat myself to pass on my thanks to 'delange' for all his help and guidance from day one, its really great that people who have also constructed the Q-Watt go out of their way to help other constructors.
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Old 22nd April 2017, 09:58 AM   #369
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Quote:
Originally Posted by calpe View Post
One Q-Watt (dual channel) up and working!
No issues at all of stability nor oscillation in any shape or form!

My life and my Q-Watt project were in my hands when i begun this project, I'm still alive and my Q-Watt is working fantastic!
Great news. Good job. Now I need to get a shift on.
Pops.
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Old 22nd April 2017, 11:23 AM   #370
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I tested the ESP P39 soft start with both transformers (2x 420VA). Starts up fine with 3.15A slo-blo fuse. P39 was modified slightly to use 33R for inrush current limiting (3x 100R 10W). Mains current is limited to 10A for approx 0.1 seconds, shared between the two PS channels.

Temperature of the three current limiting resistors increases by 1.5 deg C each start. Takes about 90s to cool.

Will try 3A fuse and 2.5A fuse later.

Pops.

Last edited by popchops; 22nd April 2017 at 11:45 AM.
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