WHY OH WHY ?

[Lampie]

Why are all the electrical machine parts(like centrifugal motor switches and table & sweep relays in the chassis)if they have double contacts, ALMOST ALLWAYS connected serial instead of parallel when you get them from the manufactures?
In my opinion this is reducing the switch/relay contacts life about 75% and give you more problems with the starting and keep running of your motors.
I have learned many years ago on school that if you devide the current between two switches or relays you will have less current at each contact(50%)running through the contacts, causing less burnmarks.
Also if one of the swithes does have a problem, the other contacts are out of the circuit too!
Is this making money or is there a special reason for this?
Please say I'm right or give me another good explanation why I'm wrong!(company's ?).
Thanks

Lamp the Bamp

Martin

[ July 24, 2001: Message edited by: Lampie ]

[Majke]

Re: WHY OH WHY ?

Good question Lampie, I re-wired relays in Limbricht and it worked out fine.
I guess it is the Amarican way of thinking [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img] Why easy if it can be done difficult [img]/content/btubb/images/%%GRAEMLIN_URL%%/wink.gif[/img]

[Jimmy Jam]

Re: WHY OH WHY ?

An easy way to think about it is 115V takes twice as many Amps as 230V. So the 115V contactors are wired in parallel to cut the current in half.
If yours were wired parallel, ours would have 2 sweep and 2 table contactors!
[img]/content/btubb/images/%%GRAEMLIN_URL%%/eek.gif[/img]
Fun stuff

[Lampie]

Re: WHY OH WHY ?

[QUOTE]Originally posted by Jimmy Jam:
[QB]An easy way to think about it is 115V takes twice as many Amps as 230V. So the 115V contactors are wired in parallel to cut the current in half.
If yours were wired parallel, ours would have 2 sweep and 2 table contactors!


------------------------------------------

J.J.
I understand why the 110 V countries have more problems than us, but why all the work to make a less good product before shipping them to the 230 countries? We don't have problems with parallel wired relays or switches, two switches wired serial gives us even more problems than one single switch...

Martin

[Jimmy Jam]

Re: WHY OH WHY ?

Martin, I know what your talking about but don't have an answer. It's like having the front desk/masking unit/circuit breaker all controlled by a imaginary master switch that turns them on & off at the same time. If you want the machine on, all of the switches get turned on by switching the master. If you want it off, all of the switches get turned off by switching the master. Why would anybody design it that way? So that all those switches would have to simultaneously be switched on and off at the same time instead of just having a single switch?
Who knows?

[Lampie]

Re: WHY OH WHY ?

Quote:]Originally posted by Jimmy Jam:
Martin, I know what your talking about but don't have an answer. [/QUOTE]
-------------------------------------------
J.J.,
This is an honest answer!
Are yours wired serial too?
Just another question...

Martin

[Jimmy Jam]

Re: WHY OH WHY ?

I love these trick questions lil-helper. [img]/content/btubb/images/%%GRAEMLIN_URL%%/cool.gif[/img] My N.C. S&T relay circuit is like yours, parallel [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img]

[ July 29, 2001: Message edited by: Jimmy Jam ]

[the old dirt man]

Re: WHY OH WHY ?

Quote:]Originally posted by Jimmy Jam:
I love these trick questions lil-helper. [img]/content/btubb/images/%%GRAEMLIN_URL%%/cool.gif[/img] My N.C. S&T relay circuit is like yours, parallel [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img]

[ July 29, 2001: Message edited by: Jimmy Jam ][/QUOTE]
GEE IS THAT IT [img]/content/btubb/images/%%GRAEMLIN_URL%%/confused.gif[/img] CRUD [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img]

[Lampie]

Re: WHY OH WHY ?

[QUOTE]Originally posted by Jimmy Jam:
[QB]I love these trick questions lil-helper. [img]/content/btubb/images/%%GRAEMLIN_URL%%/cool.gif[/img] My N.C. S&T relay circuit is like yours, parallel [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img]
-------------------------------------------
I hope you mean your N.O. circuit...

Martin

[Jimmy Jam]

Re: WHY OH WHY ?

I think they call it a combination circuit when it contains series and parallel elements like 115V SS chassis motor relays do.
BTW if you look at the block diagram the N.C. circuit breaks into parallel at the resistors. Hey, I'm learnin too.
Click here for naked bowling babes

[Lampie]

Re: WHY OH WHY ?

Like King would say "BUMP"

[TheGMan143]

Re: WHY OH WHY ?

I agree with the idea of wiring the contacts in parallel... I did the same thing with the shur-pik relays. They have 2 sets of contacts in them, but only one side is used. I rewired the harnesses to use both sets of contacts, and contact burnout problems dropped off almost completely.

[Andrew]

Re: WHY OH WHY ?

Our 8270 machines are 115V (although this is OZ and we have a step-down xformer on each machine 230-115).

The S&T contactors are wired parallel, backend relays are wired series (two contacts).

(Actually, we are now converting our backend relays to solid state - the same solid state relays used in our decommissioned AccuScore-Plus monitor power supplies, and also found in AccuScore I and II curtain-wall chassis).

Our Magic-Y s/piks use Potter-Brumfield M relays (11 pin) (but look like they were rewired a while back). I know several other centres locally that have/had m realys in their s/piks too, and one that had backend (Allen-Bradley 2 pole) relays. Not sure if they are all wired in parallel though.

Yes, current flow is reduced (and therefore life extended) when you use relay contacts in parallel. But I wonder if there's another reason why series is preferred (like our backend relays).
The only thing I can think of is when a contact fuses causing a relay to get stuck 'on' - series would still turn off, parallel would remain on (although, how would you know with a series wired relay - it would seem to function normally).

Anyway, sorry for the sermon.
:-)
Andrew.