Thread: Building an electrical control box

Originally Posted by rrobor

That I am wrong with the 3 pin regulator is your opinion not fact.

Hi rrobor,

Show me ONE manufacturers circuit or application note that has a resistor between the bridge and the filter cap.

Regards
Ray

Originally Posted by RayG

Hi .RC,

I thought you already had some spare HRC fuse holders?

For protecting the primary I would use a 100ma, HRC using the same 500v rated fuse holders as you used on the motor circuits. I note elkangarito suggests 45ma, I think you could go a little bit higher just based on the transformer being 45VA

On the secondary windings the 240v holders would be fine, 1A rating would be fine for protecting the transformer. The secondary windings are rated at 1.8 amps or so.

Regards
Ray

PS.. Ive been trying to remember the brand of a small din rail mount fuse holder... I think it was Legrand... I'll check

Go to the Legrand web site and download the terminal block catalogue Industrial - LEGRAND
look for page 129, and they list a number of different types of lever disconnect terminal blocks with fuses, the one using 5x20 fuses is the one I would think best for the transformer protection.
The part number is 371 81 (grey), or 371 82 (blue for neutral ccts). That's for the transformer secondary, you still need the higher voltage rating holder for the transformer primary.

Thanks Ray, but I was really wanting to know if the 240V holders would do after all it is 240V phase to ground... Plus they are cheap compared to 415V stuff...

Of course there is always these http://cgi.ebay.com.au/600V-10A-FS-1...item4156e58eb2

or these http://cgi.ebay.com.au/Single-Pole-R...item43a5386138

Originally Posted by rrobor

Current lags in an Inductor so there is no great surge through the relay coil, it builds up over a period so all that a resistor there will do is act as a voltage dropper and drop the coil voltage below its rating..

Hi rrobor,

Sigh... wrong again, the inrush current in a (edit, added AC) AC contactor or solenoid can be up to 10x the holding current. The thing you are missing, is that the there are actually two circuits, the electrical circuit and the magnetic circuit, when the contactor closes the poles come together and the current drops. The coil inductance is not the only factor at work.

Regards
Ray

PS.. I'll add one more thing, If you ever get swarf or foreign material jammed in a contactor so that it doesn't close the poles, the coil will soon burn out due to excessive current.

Originally Posted by RayG

Hi rrobor,

Show me ONE manufacturers circuit or application note that has a resistor between the bridge and the filter cap.

Regards
Ray

Hi rrobor,

Here is a quick way to look at lots of power supply circuits. Using google image search

power supply schematic - Google Search

See if you can find just **one** that has a resistor between the bridge and the cap.

The only **possible** reason you might do that is to try and make a low pass filter into a crude power supply of sorts.

Regards
Ray

Sorry not getting into this sort of rubbish. All I ask is the builder of this checks on the internet as to current leading and laging, its first year electronics. Once you do that find any commercial power supply you like, you will find a surge limiter in it either just before or just after the bridge, doesnt matter which
Your contactor is 1 coil and one coil will conform to he laws you can find on the internet easilly, Dont believe me, why should you, but please just check.

I knew I should have sent the SN21...and not the SN10

oh well he will have to live with 200000 operations...probably outlast the ole fart anyway......sorry RC...hehehe

Originally Posted by .RC.

Thanks Ray, but I was really wanting to know if the 240V holders would do after all it is 240V phase to ground... Plus they are cheap compared to 415V stuff...

Of course there is always these 600V 10A FS-10 Single Pole 6 x 30mm Fuse + Fuseholder (eBay item 280630759090 end time 18-Mar-11 07:35:18 AEDST) : Industrial

or these Single Pole RT14-20 380V Fuseholder for 10 x 38mm Fuse (eBay item 290534744376 end time 17-Mar-11 15:55:14 AEDST) : Business Industrial

Hi RC,
Voltage wise, 240v fuse holders are probably adequate. I'm not sure what the safety implications are, I'm used to having systems designed with door interlocks so that everything powers down as soon as you open the enclosure. Just make sure you keep safety as the highest priority, and eliminate any chance of accidental contact with live terminals when changing a fuse.

Someone else might be able to elaborate on what the regulations have to say.

Regards
Ray

Originally Posted by rrobor

Sorry not getting into this sort of rubbish. All I ask is the builder of this checks on the internet as to current leading and laging, its first year electronics. Once you do that find any commercial power supply you like, you will find a surge limiter in it either just before or just after the bridge, doesnt matter which
Your contactor is 1 coil and one coil will conform to he laws you can find on the internet easilly, Dont believe me, why should you, but please just check.

Hi rrobor,

No problems, or hard feelings, it's been an interesting discussion.

Regards
Ray

Originally Posted by rrobor

Sorry not getting into this sort of rubbish. All I ask is the builder of this checks on the internet as to current leading and laging, its first year electronics.

Well I only got as far as "Funway into Electronics 2"

And that was 20 years ago..

I think I will just use one active and Earth to get 240V and then use a wall wart.. What say ye?

Originally Posted by RayG

PS.. I'll add one more thing, If you ever get swarf or foreign material jammed in a contactor so that it doesn't close the poles, the coil will soon burn out due to excessive current.

Pardon me, It's just me being pedantic again...

All this talk about 'in-rush'!!!

This is an DC coiled relay - DC coils are resistive (impedance)current limited. There is no in-rush as such! It is a bloody inductor too! - there is no inrush current on an inductor - it is the opposite - the current exponentially builds up!!!

AC coils are inductive (impedance) current limited. When the contactor is open, the inductance is low and there is significantly higher current flow ("in-rush" if you like) due to the 'air gap'. However, when the contactor closes (and the pole piece forms part of the magnetic circuit), the inductance rises and the current drops.

Therefore, a DC contactor will be fine with "foreign material jammed in a contactor so that it doesn't close the poles" but an AC one won't be too happy.

I'll go away now.

Originally Posted by chrisp

Pardon me, It's just me being pedantic again...

All this talk about 'in-rush'!!!

This is an DC coiled relay - DC coils are resistive (impedance)current limited. There is no in-rush as such! It is a bloody inductor too! - there is no inrush current on an inductor - it is the opposite - the current exponentially builds up!!!

AC coils are inductive (impedance) current limited. When the contactor is open, the inductance is low and there is significantly higher current flow ("in-rush" if you like) due to the 'air gap'. However, when the contactor closes (and the pole piece forms part of the magnetic circuit), the inductance rises and the current drops.

Therefore, a DC contactor will be fine with "foreign material jammed in a contactor so that it doesn't close the poles" but an AC one won't be too happy.

I'll go away now.

Hi Chrisp,

Don't go away, you are correct... I had AC contactors on the brain, for some reason that escapes me...

I'll also apologise to rrobor for confusing the issue.. AC with DC contactors.

Regards
Ray

Originally Posted by RayG

I'll also apologise to rrobor for confusing the issue.. AC with DC contactors.

and Also to eskimo.....I too am confused...all this impedance/inductive and resistiveness stuff ????

I'll just stick to ac relays and the like....but I do note that some time delay relays I now get are ambidextrous...they accept ac/dc 12-240v input all at the same terminals without flicking anything...and dont you 2 go on about how they work...i dont care...they just work and thats all I need to know...clever little things they are

Originally Posted by eskimo

...and dont you 2 go on about how they work...

Hi Eskimo,

And I had a three page write-up prepared on how they work...

Regards
Ray

PS

Originally Posted by eskimo

.
and Also to eskimo.....I too am confused...all this impedance/inductive and resistiveness stuff ????

Ok, you too.. BTW, it's reactance, but that would be joining the pedantic club.