Radial wiring?

[dmroeder]

Today at work, there was a discussion on what "Radial Wiring" is and how it applies to 3 phase. I looked around on the internet about the subject and I couldn't find a clear answer. I was wondering if someone could help me out, or point me in the right direction to understanding Radial Wiring?

What I gathered was that if you had to wire 3 motors (3 phase) in a "radial" circuit, I would come from somthing like a main breaker and daisy chain to each motor (haveing to use the same size wire that feeds the breaker). As opposed to coming from a distribution block to each motor (where I could size the wire for each motor). Am I on the right track? Or did a bunch of garbage leak out my fingers onto the internet?

 

[tim in pa]

the term radial usually implies that legs come out from a (common) point at differant angles. in other words, ph A would have several wires coming from it to several motors, then the same for ph B and ph C. i can't imagine. daisy chaining 3 ph motors. the first legs would have to carry the current for all the motors, etc. but, i don't believe i have ever heard the word radial used with electrical wiring before.

 

[dmroeder]

Thanks for the reply Tim. A customer of ours requested "Radial" wiring on all motors 5HP and below. I was kind of lost. Some people thought that it meant we had to use certain types of connectors. I couldn't really make any sense of it. Everything that read on the subject had to do with single phase wiring.

After some clarification from the customer, it turns out what they wanted was no breaks from the control panel to the motor.

 

[Outrage]

Radial, is a term used commonly used in the UK to demote the situation of daisy chaining outlets fed from one end only (as opposed to a ring)Typically used in single phase domestic wiring.

At work we have a radial 3phase cable that runs alongside our conveyors feeding our Moeller ASI motor starters that are mounted next to the motor on each segment of conveyor. It's a good system that drastically reduces the number of individual cables all fed from a single source. All our motors are relatively small and they are sequenced start and stopped so the cable is relatively small.

Cheers,

Lee

 

[dmroeder]

Thanks for the reply Outrage.

So you make a run to the first starter, then from the line side first starter, you run to the second starter and so on? Am I understanding this correctly?

 

[Tark]

After some clarification from the customer, it turns out what they wanted was no breaks from the control panel to the motor.

If 'no breaks' is referring to no disconnects, I would make sure this doesn't violate the Disconnecting Means of the NEC.

 

[dmroeder]

Tark,

There is a main disconnect located inside the control panel where all the motor starters for the piece of equipment are located. It is lockable from the outside of the panel.

I believe they were making sure that we don't run motor wiring through JB's (which we don't anyway). All the motor's are within 12 or so feet from the control panel.

 

[Outrage]

Hi DM,

In our application our supply cable runs to a "T" tap off point where it branches off to supply our first motor starter with the other leg continuing on to the next tap off etc etc. In simple terms your supply cables comes into the motor starter terminals and from the same terminals leaves the unit to continue on to the next. Power does not flow through the Load (Output) side of the starter to the next unit, only from the Line (input) side to the next unit. (If the terminology across the pond is the same!).

You're application appears to be different from mine (reading your latest posts). In that my contactors are remote from my main panel whereas your contactors are all in one place feeding remote equipment. The differences are that my main panels are relatively small with one power and one network cable that services all motors whilst your panel will no doubt be larger and have a power cable individually feeding each motor.

If the motors are only a short distance away you might as well cable them all invividually direct from the panel. Mine cover a large area. If this is what is required it would have been simpler for your customer to say wire them direct with no JB's/local isolators inbetween etc - I suspect he's mixing his terminology!

Hope this helps and i've not confused matters,

Lee

 

[dmroeder]

Thanks for the information Outrage, I appreciate it.

I understand that you wouldn't be tapping off the load side of the starters.

This is not my project, I just overheard the discussion. I wanted to make sure I understood exactly what was going on before I gave my input. I heard a pretty wide range of definations for radial wiring. I didn't want to cause a fuss without having at least some idea of what I was talking about!

Your application makes sense, and ours doesn't. The guy running the project is making assumptions on the subject and I wanted to make sure that things were clear. We have been bit pretty badly for missing what we thought were minor details.

We do wire our starters individually, it just threw me when I saw this in our specification sheet for this particular job.

Thanks for everyone's time.

 

[ndzied1]

For those wondering, Outrage is probably using something like this:

http://www.moeller.net/en/industry/switchgear/switch_protect/drives_decentral/rapid_link.jsp

I don't believe it has UL approval for use in the states.

Disclaimer, I work for a Moeller Distributor.

 

[PeterW]

For those wondering, Outrage is probably using something like this:

http://www.moeller.net/en/industry/switchgear/switch_protect/drives_decentral/rapid_link.jsp

I don't believe it has UL approval for use in the states.

Disclaimer, I work for a Moeller Distributor.

Those are the exact units we have here for our conveying systems. The devices are plug only connections for 415VAC and ASi.

Both the above are supplied from flat cables with the 'spike' type connection adaptors (yes even the 415VAC).

 

[Outrage]

Hi Norm,

Yes they are the units, makes a big difference being able to use distributed control like this for me. Most of the previous companies ive done projects for were stuck in their ways and preferred massive MCC's and loads of cabling.

PeterW, it looks like we have the "Cheeper" version of the power supply cabling, ours is round cable and enters tap off's with screw terminals and a plug and socket for the starter supply - although the ASi network uses the profiled cable and the vampire connectors. Does your power cable run exposed down the side of the conveyors? ours is all contained in trunking which may explain the differences of cable.

Cheers,

Lee

 

[PeterW]

Does your power cable run exposed down the side of the conveyors? ours is all contained in trunking which may explain the differences of cable.

I'm actuially sat next to a panel at the moment with a conveyor the other side. The cable runs in basket type tray, and is cable tied to the side of the basket (inner) by using some plastic inserts that fit into the basket frame.

Its actually run in round cable from the panel, which fits into an adaptor on the basket where the drives start, one side round cable the other flat profiled which has female sockets attached 'vampire' style at every motor.

The cable to the motor has a plug at each end as the motor also has a female socket at the connection box.

On a recent job we also used inverters that replaced the connection boxes and sat on the motor.

 

[Outrage]

We also have the integral pumps/invertors although ours are only on our packaged plant pump skids which are Danfoss I think - seems to me to be the way to go but as always you can't tell some companies i guess!

Cheers,

Lee.

p.s. who's manufacture are your conveyors and what industry are they in?

 

[PeterW]

The inverters we used were Danfoss, unfortunately we were the guinea pigs for these types of drives and had apprx 200 conveyors set up with them before we found out there were build issues.

They did replace all 'suspected' faulty units, more than 150 of them. We also tried Siemens as a fall back in case the new ones failed.

The new ones were OK as were the test Siemens ones, but the next project, another 400+ drives were built with convensional panel mounted inverters.

I would imagine they are fine now, we just got caught out by a budget manufacturing system when they were first introducing these drives.

The company I'm working for now is a large Dutch company manufacturing conveyor systems for Airports baggage handling. All state of the art control.