Discuss Problem with contactors wired in parallel in the Industrial Electrician Talk area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

if the problem arose just after the contactors were changed, i suspect that whoever cahanged them got the connections wrong, maybe just 2 wires crossed, or maybe 1 termination is poor.
 
Make sure we can see the coil volts on a meter in the video!
 
OK update, (still no further ahead)
Meggered the cables to ground, all good
Did a continuing test between S1 and it's solenoid and s2 and it's solenoid

Also measured the hold and pull in coils within the solenoid. They were both near enough the same resistances on both solenoid 1 and 2


Just waiting on the engine pre heating before I measure the coil voltages.
[automerge]1572510302[/automerge]
OK video. S
it appears my cheap UNI-T isn't fast enough.
I'll try my fluke

Problem with contactors wired in parallel {filename} | ElectriciansForums.net
 

Attachments

  • Problem with contactors wired in parallel IMG_20191030_201756 - EletriciansForums.net
    IMG_20191030_201756.jpg
    118.9 KB · Views: 35
  • Problem with contactors wired in parallel IMG_20191031_072938 - EletriciansForums.net
    IMG_20191031_072938.jpg
    100.9 KB · Views: 30
Last edited:
The Albright contactors S1 and S2 use magnetic blowout techniques to improve their ability to break high dc currents quickly as in your application. It is important that the high current contacts are connected with the correct polarity - one of the two NO contacts will have a + beside it.

Secondly, being dc coils, I wonder if the energisation of S1 and S2 is augmented by permanent magnets in their construction - making them magnetically polarised. In which case the polarity of the dc applied to the coil will matter. I suggest you check the polarity and way the connections have been made to S2 by comparing with S1 and using your DVM; try swapping over the connections to the S2 coil.
 
Could do with seeing the full diagram,of the contactor drawing. They seem part parallel and part sequential.
I take it this is generation,and not a train? how old is the unit,and does it have LOP control?
 
The coils are parallel in the dwg, OP says they are, he's even tried paralleling them with new bits of wire. The fault stays put when the contactors are interchanged or exchanged for different ones. Therefore it seems to be something to do with the physical position e.g. magnetic interaction, possibly indicating marginal operation so that something that shouldn't normally make a difference now does.

Suppose there is a high-resistance connection and once the motor circuit closes the voltage falls to just barely enough to hold the contactors. Now suppose something is either helping S1 stay in, such as a steel casing component behind it bolstering its magnetic circuit, or something is hindering S2 staying in such as magnetic interference from a contactor adjacent. Normally these factors wouldn't affect operation but the marginal holding volts amplifies the difference. Or, as Marconi says, the polarity of S2 is wrong but I don't recall these being PM assisted.

It's all a bit far fetched given that the pull-in is 66% nominal, and drop out 10%, so there's a huge margin of hysteresis to keep it in once it's in. But I am looking for anything that doesn't violate laws of physics.

Scope trace of coil volts would be good! Also, it would be interesting to know what happens with the motors fuse out and the pull-in coils disconnected from the motors and connected in series. This would allow it to get to the point the motor load comes on to the battery, without that actually happening. Would need to keep the test brief or break the pull-in coil connections once in, to stop them cooking. Also need to make sure they actually go in and don't stick with the pinion teeth out of mesh as the motors won't be trundling round as they reach the ring gear.
 
Just thought of another worthwhile check,the drawings show a simplified layout of the two contactors,which does not always correlate to the fact they are handed.
They are,as marconi mentioned,polarity critical,in their operation,so well worth checking the markings.
 
Hmmm never thought of the coil being polarity sensitive (I'm more and ac rather than dc guy)
Certainly something to look into.

Its got to be something stupid.

I thought I found something earlier, the link between SW and 228 on solenoid 1 was wired to 227, but alas still the same when I changed it. :(


I'll keep you posted on this absolutely mystifying problem. In 20 years of being an industrial spark I've never come across anything quite like it.
[automerge]1572525749[/automerge]
The Albright contactors S1 and S2 use magnetic blowout techniques to improve their ability to break high dc currents quickly as in your application. It is important that the high current contacts are connected with the correct polarity - one of the two NO contacts will have a + beside it.

Secondly, being dc coils, I wonder if the energisation of S1 and S2 is augmented by permanent magnets in their construction - making them magnetically polarised. In which case the polarity of the dc applied to the coil will matter. I suggest you check the polarity and way the connections have been made to S2 by comparing with S1 and using your DVM; try swapping over the connections to the S2 coil.


I think you might be on to something regarding the magnetic blow out of the contactors. (I've never seen nor heard of such a thing before) but it could be that the starter motor itself has a short, which is making the contactor force itself open, but the pull in of the coil is still in effect so it pulls the contact close again. Repeating itself until the other starter motor gets the engine running.

That could also explain the massive arcs you get on S2 when it pulls in. Where S1 doesn't.
I'll see about getting the starter motors changed. (apparently 3000quid a side :))
 
Last edited:
Please can we see the coil volts at the coil terminals. Pleeeeease!
 
Re# 29: That could also explain the massive arcs you get on S2 when it pulls in. Where S1 doesn't.

I have just phoned the technical department at Albright who make S1 and S2. I was told the coils do not have any sensitivity to polarity - but I would still see if it made a difference.

I asked about the nature of the arcs if the polarity at the high current contacts was the wrong way round. The magnetic arc quench mechanism expels the arc away from the contacts when the polarity is correct. When incorrectly polarised, the arc is drawn inwards causing damage to the high current switch mechanisms.

AS you observed a difference in the intensity of the arcs, the brighter display of arc appears correct for S2 and possibly is dimmer on S1 because of incorrect contact polarity. So check by voltage measurement and markings on S1 and S2.
 
Where's the 'winner' icon gone?
 
Could do with the drawing showing all four contactors,as that drawing shows battery voltage being switched,not 110v DC.
[automerge]1572560512[/automerge]
Also,does this have pneumatic start option?
 
Last edited:
hmmmnz: Re-reading my notes of the call I made to Albright, the technical said that the SW200A-33 is bespoke to original equipment manufacturer by which I assume he means whoever made the controller to start the diesel engine you mentioned. He thought it was a type used in railway locomotives. I have been unable to turn up in any search or dc contactor catalogue the SW200A-33 nor anything when searching against the Coil type 17-167 Ohms and Coil 00V.

What I wonder those is if you have the correct type of dc contactor for the S1 and S2 role because there are a myriad of variations of the SW200 type. Have you a parts list you can check against? And, I have to ask are the substitute contactors both the same part number? And identical to the ones removed?

When I studied your video clips I can't say I thought the voltage readings were unexpected - a dip in voltage as the SMs are energised and start turning, a gradual rise in voltage and then a brief reading of 170V as the SMs and the S1 and S2 are de-energised. An AVO across might show better the voltage v time across S1 and S2. Even better if you could insert the AVO in series with the coils of S1 and S2 to measure the current v time.

The SW200 can be bought with different spring stiffnesses to increase the rapidity of opening the contacts. Stiffer springs mean more power is required from the coil and thus Ohmic heating which in turn affects the duty rating of the contactor. The stiffest spring is fitted in those contactors which have the lowest duty rating. This would seem appropriate for contactors switching high current inductive loads at 110Vdc only used occasionally as in starting an engine. I wonder then if the contactor in the S2 position you are fitting have a coil which cannot provide sufficient force to pull against the spring and make a tight closure of the high current contacts - leading to the arcing - which will modulate the 110V dc supply voltage - which will modulate the current through S2 (and S1) and thus some variation in the force which is closing the contacts. And superimposed is the cranking current pulses as the piston - cylinders are compressed.

See under D and 'Duty' in:
Glossary - Albright - https://www.albrightinternational.com/glossary/

So some higher resistance in the wiring to S2's coil resulting in reduced current through S2's coil? I'd be taking a good look at the ring crimps to S2 coil and even swapping them for some new 1.5mm2 say temporarily.to bowl out dodgy paralleling wiring.
 
Last edited:
Could do with the drawing showing all four contactors,as that drawing shows battery voltage being switched,not 110v DC.
[automerge]1572560512[/automerge]
Also,does this have pneumatic start option?


The drawing shows all 4 contactors.
Scc1 Scc1 S1 and s2 are the 4 contactors in the start circuit. The batteries are 110v dc
No pneumatic start option is fitted

What I wonder those is if you have the correct type of dc contactor for the S1 and S2 role because there are a myriad of variations of the SW200 type. Have you a parts list you can check against? And, I have to ask are the substitute contactors both the same part number? And identical to the ones removed?
Yeah these are identical to the ones removed, and supplied for this job.
I've substituted the contactor from S1 and the old contactor into S1 position, they all react the same way

Problem with contactors wired in parallel {filename} | ElectriciansForums.net

Watch the video on the previous page. That's as good as I can get with the 2 meters I have available
Considering S1 pulls in fine and it's wired I parallel with S2 I doubt the voltage is the problem
 
Hmmmnz: Yes, not a voltage problem but maybe a reduced current problem through S2. Have you/will you substitute the wire links which places S2 in parallel with S1? It is not unknown for a wire to be overcrimped inside the crimp and break in such a way that there is no metal to metal contact for current flow or which produces higher resistance.

Could you place one of your DMM's in series with S1 and the other with S2 and compare the coil currents please?

And to humour me, could you swap over the polarity to S2's coil.
 
Last edited:
The drawing shows all 4 contactors.
Scc1 Scc1 S1 and s2 are the 4 contactors in the start circuit. The batteries are 110v dc
No pneumatic start option is fitted


Yeah these are identical to the ones removed, and supplied for this job.
I've substituted the contactor from S1 and the old contactor into S1 position, they all react the same way

Problem with contactors wired in parallel {filename} | ElectriciansForums.net

Watch the video on the previous page. That's as good as I can get with the 2 meters I have available
Considering S1 pulls in fine and it's wired I parallel with S2 I doubt the voltage is the problem
Thanks for posting the videos to the forum! - What a star. You're possibly the first genuine person to post a video (apart from me for testing). So this will go down in history for the forum. :) Thanks.
 
es, not a voltage problem but maybe a reduced current problem through S2. Have you/will you substitute the wire links which places S2 in parallel with S1? It is not unknown for a wire to be overcrimped inside the crimp and break in such a way that there is no metal to metal contact for current flow or which produces higher resistance. Could you place one of your DMM's in series with S1 and the other with S2 and compare the coil currents please? And to humour me, could you swap over the polarity to S2's coil.

I've got another set of wires doubling up the parallel circuit. But it's wired positive to one of the contactors and the negative to the other with the loops in between. So if it was that it'd also take out S1 contactor as well.

I'll flip the polarity on the coil now and see if it makes a difference
 
hmmmnz: I have asked Albright to send me the datasheet for your contactor. Watching your two videos we can see the voltage dip down to 50V in one clip and 60V in the other.

The force of a solenoid is:

F = (n x i)2 x magnetic constant x a / (2 x g2)

where n is number of turn, a is area and g is length of air gap. So, the force is proportional to the current squared or to the applied voltage squared if the coil resistance R is constant.

What this means is the the relationship is parabolic:

Problem with contactors wired in parallel parabola - EletriciansForums.net

where y is force F and x is current I.

So, the force produced by the solenoid(S1/S2 coil) increases more rapidly as the magnitude of the current/voltage increases; or the force decreases more rapidly as the magnitude of the current/voltage decreases. The effect then is if the coil of the contactor S1/S2 is first energised with a low voltage the pull in force will be lower than at a higher voltage - the contacts may not then close with sufficient force to make a good enough conduction region for the starting current. Some arcing will occur tending to push the contacts apart which reduces the starting current a little and at the same time increases the applied voltage to the coil - the contacts are then pulled together with a slightly greater force. The starting current increases once again but the contacts are not made well enough so there is some more arcing tending to push them apart. This 'hunting' continues until the start current has dropped to a sufficient level that the contact pressure can pass this current without arcing.

The long and the short of it is I wonder if the problem is not S2 per se but the out of specification drop in applied supply voltage because:

1. The 110V battery is not fully charged.
2. The battery has aged so its internal resistance has increased limiting its ability to provide high current without excess volt drop.
3. There are some high current supply (+ and -) conductors which have poor connections including on the battery.
4. The starter motors have faults or are struggling to start the diesel for some reason.

Quite why the problem only occurs for S2 I suggest (don't know) is because of some magnetic interaction between S1, S2 and the magnetic fields around the high current conductors which tends to promote the hunting effect for S2 but not/not as much for S1. Or the polarity matters in the sense it can reduce or aggravate hunting.

Can you charge up the 110V battery to see if it has an effect on the problem?
[automerge]1572605355[/automerge]
I have to go out now but here is what I have from Albright:

Type: SW200A-33

Coil Voltage (V) 72 INT DC

Coil Resistance (Ohms) 167

Pull In Voltage (V) 50.0 Maximum

Drop Out Voltage (V) 16.0 Maximum

Coil Power Dissipation (W) 31.04

Additional Features

RED ADHESIVE DOT POSITIONED ON FRONT OF TOP COVER , SAME SIDE AS

3-WAY TERMINAL BLOCK - SEE DRAWING 2155-113.

SPECIAL LABEL FITTED STATING COIL RESISTANCE, SEE DRAWING 2155-113.

SOCKET SET 2BA GRUB SCREWS MUST BE USED TO LOCK AUXILIARY PLUNGER.

All figures above are stated at 20 degrees Celsius
 

Attachments

  • sw200A-33.pdf
    250.1 KB · Views: 2
Last edited:
Hi just what type of 110v dc starters are fitted?
All the ones i have dealt with have been 24v dc,and/or pneumatic start.
 

Reply to Problem with contactors wired in parallel in the Industrial Electrician Talk area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock