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Old 29th December 2009, 01:44 PM   #511
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Originally Posted by AndrewT View Post
If we take current through a series connected capacitor to our circuit (soft start control), do we raise the power/load factor of our total household demand?
Such a capacitive load will in theory improve (= increase) the power factor, if you operate inductive consumers like CFLs, SMPSs or inductive motors in your household at the same time. The better the power factor, the more of the apparent power turns into real power and the more of it will be measured by the electricity counter.

The trick of a bad power factor is that we as consumers don't have to pay for the reactive part. That is also part of the swindle with CFLs. The energy counters that are still in use only measure real power. That is why your electricity supplier obliges you to compensate for reactive loads. E. g. here in Germany you can use up to 130 VA of reactive loads per phase without compensation. Once you pass that figure, you need to compensate to a power factor within -0,95 and +0,95.
In the near future we will all get electronic counters that can measure apparent power and calculate power factors. That means, we won't need to buy compensation plants, but will then have to pay for the apparent power and probably an additional fee for extremely bad power factors, too.

The apparent power is, what needs to be generated and what leads to heat dissipation across any impedance. This became obvious in Tripmaster's light bulb tester and in audio1st's measurements. If you work with reactive loads, all components have to be calculated to withstand the apparent current, not the lower real current. E. g. if you connected that soft-start module to a transformer with a 240 V secondary, you could not use a 2 VA transformer and think: "Hey, I have more than 100 % spare for that 0,9 W relay coil." The transformer would be loaded with 20 VA. Cables, rectifiers, wires, everything needs to be made for 20 VA, even if the electricity counter only shows 2 W of average consumption.
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Old 31st December 2009, 05:32 PM   #512
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Hi

Ive been hunting around for a replacement soft-start circuit and wondered if anyone can provide helpful opinions based on the following kits/circuits? It appears most of the kits run directly from the mains and not via a separate DC power supply.

http://avondaleaudio.com/diy-audio/soft-start-module/

Avondale supplies the PCB and relays for about £10, they also supply a pre-built board but I would rather build it it myself and save money. I will need to source the other components separately. The company is UK based.


Ska Audio SoftStart

Connexelectronic

Soft-Start Circuit For Power Amps

L C Audio Technology / Soft Start

sjostromaudio.com - SST01 Softstart for toroid transformers


Thanks
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Old 1st January 2010, 10:01 AM   #513
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Hi Richard,

I think you could just remove the rectifier from the soft start board and use it with a small 9V transformer?

Barry
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Old 1st January 2010, 04:10 PM   #514
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I'll be buying the one from Connexelectronic shortly. Of all the soft starts I've seen available, it's the best looking one at a good price. It has it's own transformer, uses thermistors, has an actual timer for the relay and has a remote input if you want to set up remote power toggling.
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Old 4th January 2010, 12:07 PM   #515
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Hi Richard,

I think you could just remove the rectifier from the soft start board and use it with a small 9V transformer?

Barry
Thanks Barry

I'll have a go at this before purchasing another soft-start
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Old 4th January 2010, 01:55 PM   #516
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I'm going order some parts today/tomorrow. What 'VA' rated transformer should I go for?
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Old 4th January 2010, 02:05 PM   #517
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give us a clue.
For the soft start alone or to power the Queen Mary.
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Old 4th January 2010, 02:08 PM   #518
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give us a clue.
For the soft start alone or to power the Queen Mary.
Just the soft start as per Audio1st previous post
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Old 7th January 2010, 09:32 PM   #519
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Hi Richard,

I think you could just remove the rectifier from the soft start board and use it with a small 9V transformer?

Barry
Hi Barry

I removed the rectifier from the soft-start board tonight and connected a 9VAC transformer, wired in parallel so as to power the soft-start separately. I then connected the AC supply from the IEC mains inlet to the s-s board and 9V transformer. The relay clicks as per normal, and I am getting 233V on the s-s output. After cutting the power I touched the 47R power resistor and it felt warm.

Click the image to open in full size.

The bulb tester doesn't glow, like it did before the mod

Is there anything else I can do to check the s-s is working correctly?

Thanks for the practical tip!
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Old 7th January 2010, 10:15 PM   #520
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Hi Richard,
Glad to hear it still clicks. Once the relay has clicked that should short out the resistor and will no longer be in circuit, leave it on for awhile and the resistor should cool down. Turn off before touching though...
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