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Slipring Contacts

05/12/2020 4:31 AM

I am designing a cable reel for a mining application the voltage is 1000V AC and the current is 360 Amp and I am looking for a design for a slipring contact. The rotation is bidirectional. The rotating speed is very low about 1 rotation per hour. I could not find what I am looking for on Google maybe someone can give me some pointers. I have in mind a brass or bronze ring of 250mm diameter and 40mm wide with Tufnol dividers and spacers. Would a brass wiper contact be acceptable? For the spring action I am considering copper leaves.

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#1

Re: Slipring Contacts

05/12/2020 5:48 AM

<...pointers...>

The sorts of things that are used at rotating restaurants might be applicable, as the rotation speed is of the same order.

Examples include the CN Tower in Toronto:

and the Post Office Tower in London:

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#2

Re: Slipring Contacts

05/12/2020 6:44 AM
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#12
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Re: Slipring Contacts

05/13/2020 2:52 AM
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#13
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Re: Slipring Contacts

05/13/2020 3:45 AM

Thanks it looks promising, I will contact them.

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#3

Re: Slipring Contacts

05/12/2020 7:01 AM

<...brass wiper contact...acceptable?...>

The rest of the forum is not in a position to review the suggestion in view of the end Client's criteria and determine acceptability.

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#4

Re: Slipring Contacts

05/12/2020 11:20 AM
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#9
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Re: Slipring Contacts

05/13/2020 1:53 AM

I am not in the cable reel business and I do not intend to go there but the application we have is very special and non of the reel manufacturers have anything close to it.

We have been in contact with reel manufacturers without success.

This reel does not only have to hold cables but hoses as well. Furthermore it must track a machine and either reel in or out depending on the situation. It will be PLC controlled and will have to cope with harsh underground conditions. This is not an off the shelf item and the quantities are low.

Thanks for your interest.

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#15
In reply to #9

Re: Slipring Contacts

05/13/2020 5:25 AM

On the BE 45R drill the cable reeler was driven by a reduction drive from a drive motor but in payout as the drill drove the cable reeler was in freewheel with drag and only drove in rereeling mode.

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#19
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Re: Slipring Contacts

05/14/2020 5:10 AM
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#10
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Re: Slipring Contacts

05/13/2020 2:02 AM

I am not looking at going into the reel business.

Thanks for you interest but the reel suppliers you mentioned make toys. We are looking at something much bigger.

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#5

Re: Slipring Contacts

05/12/2020 3:04 PM

Why design when simply purchasing is an option?

My only design suggestion is to distribute each connection across multiple slip ring contacts. This way loosing only one contact momentarily will not interrupt service.

Since this is for mining application you may have to encase the contacts to meet explosive gas concerns.

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#6

Re: Slipring Contacts

05/12/2020 4:39 PM

The mining environment is very harsh and your speed is very very slow which is very hard to design for, your better to just look at slipring manufacturers to supply or custom build something, especially if the slipring has to transmit a PWM signal from a variable speed drive.

We used to build something similar but with a much smaller rating (and a lot of trial and error) and it was a real headache. Brass wiper likely won't work, at the least you will likely need multiple proper carbon brushes (of a certain grade) to ensure low contact resistance due to the slow speed.

This is quite a hard application, talk to slipring manufacturers for advice and a solution.

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#7

Re: Slipring Contacts

05/12/2020 10:43 PM

BE already have mastered this application for drills, shovels and draglines.

They use a bronze shoe under coil spring pressure.

Maybe you could get a look at one of their setups or maybe stop trying to reinvent the wheel (slipring).

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#11
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Re: Slipring Contacts

05/13/2020 2:05 AM

Sound interesting but who are BE?

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#14
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Re: Slipring Contacts

05/13/2020 5:22 AM

Bucyrus Erie is BE, they make cranes, drills, shovels, Draglines.

The bronze shoes run on steel slip rings and work on various voltages though I have only maintained ones on 6.6KV.

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#17
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Re: Slipring Contacts

05/13/2020 9:27 PM

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#8

Re: Slipring Contacts

05/13/2020 12:14 AM

I agree with the others that it is probably better to use a commercially available slipring assembly.

If you do plan on making something yourself, pure copper is certainly NOT appropriate for spring material. There are many alloys of copper available; Unfortunately, the alloys which are "springy" are generally poorer conductors than the softer alloys. You'll need to choose an alloy to make a compromise between stiffness and conductivity.

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#16

Re: Slipring Contacts

05/13/2020 6:19 PM

Copper loaded carbon brushes on a copper slip ring would be a good starting point,it should be no problem on a ring of the dimensions you quoted. Check with the carbon brush Mnf re current carrying capacity so you can design the layout. There are plenty of off the shelf brushes of the type you need.

Your main problem is to insulate the sections for 1000V AC and enclose in appropriate housings.

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#18
In reply to #16

Re: Slipring Contacts

05/14/2020 1:47 AM

Thanks Garth.

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#20

Re: Slipring Contacts

05/14/2020 5:43 AM

<...pointers...>

These behemoths had articulating pipework, carrying steam at boiler pressure:

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#21

Re: Slipring Contacts

05/14/2020 12:23 PM

If these are continuous slip rings, I am accustomed to copper slip rings running against graphite brushes. These will need to be maintained oil free and sealed against contamination by nonconductive particles, oils and greases. I have also seen silver slip rings run against graphite as well in more demanding installations.

You might want to consider using liquid metal brushes against a metal slip ring. These are used in high voltage/high current contactors which are self renewing to avoid contact arcing and burning. Commonly the liquid metal is contained in an inert atmosphere to prevent any oxidation. In the past I have seen these using mercury as the liquid metal, but there are other low melting point alloys available to meet ROHS requirements.

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