Motor connectivity to PLC

ramrap.r · Jul 9, 2006

In present configuration We are laying 8 wires 4 For Feedback & 4 For Start & Stop Output from Motor feeder to PLC.

Now, in future I want to save on this Cabling cost. Is their any method is there where we can send all this signals with less cables.

Any help in this regard will be highly appriciated.

Thanks.

rdrast · Jul 9, 2006

Yes there is, no there isn't, and Maybe.

I don't know what you are doing, but if I assume you have a motor control center somewhere with buckets, then you can often either order them with a networkable control system (like DeviceNet), or you can put a cabinet right next to the MCC with remote I/O drops.

Both will cut down on the actual command/status/control power/control common signal lead wiring, but depending on the actual number of motors might be more expensive an option.

A $1000 remote I/O drop might not be worth it for the control of one motor, but could be very cost-effective for 5, 10, or 20.

PeterW · Jul 9, 2006

Also depends on PLC, device net is predominantly AB, if you use another system like siemens then asi would be a possibility.

Both types would also cater for all your other I/O signals like PEC's, proximity switches, valves, etc.

JohnW · Jul 10, 2006

ramrap.r said:
In present configuration We are laying 8 wires 4 For Feedback & 4 For Start & Stop Output from Motor feeder to PLC.

Now, in future I want to save on this Cabling cost. Is their any method is there where we can send all this signals with less cables.

Any help in this regard will be highly appriciated.

Thanks.

What are you using as a motor feeder? I would normally only use 4 or 5 wires. 24vdc, ovdc, start, running, (stopped optional).

rsdoran · Jul 10, 2006

I read it that he had 4 motor starting devices, probably contactors, that needed one wire for each start and aux contact. Technically there should be a 9th wire for the common/neutral involved.

AS-Interface is designed for this purpose, it uses a 2 wire cable that can transmit power and signals to devices. For more info on AS-i look here: http://www.as-interface.com/

There are fielbus systems too:
Controlnet: http://www.controlnet.org/

Devicenet, which is not primarily AB;
http://www.odva.org/index.htm

Ethernet I/P information is at either controlnet.org or odva.org.

Profibus: http://www.profibus.com
Profibus offers free web training;
http://www.profibus.com/pb/support/train/#index_9

CANopen; http://www.canopen.org/

ramrap.r · Jul 11, 2006

Thanks for raply

JohnW said:
What are you using as a motor feeder? I would normally only use 4 or 5 wires. 24vdc, ovdc, start, running, (stopped optional).

Thanks for your reply. For Feed back of motor i.e Run & Trip We are using 24 V DC while for O/P We are using 230v AC.

JohnW · Jul 11, 2006

In that case you need 5 wires:

24vdc, run, trip

230vac start signal and 0vac (or n)

I use 24vdc only on PLC i/o and fit interface relays to switch higher voltages.

Your 5 core cable must be rated at at least 300v insulation.

rdrast · Jul 11, 2006

You know, the first question we ALL should have asked, is:

How far is it from the MasterControl (pushbutton, PLC, etc) to the Starter, and then How far is it from the Starter to the Motor.

{edit}
And, if there is a PLC being used, what kind?

rsdoran · Jul 11, 2006

rdrast said:
You know, the first question we ALL should have asked, is:

How far is it from the MasterControl (pushbutton, PLC, etc) to the Starter, and then How far is it from the Starter to the Motor.

{edit}
And, if there is a PLC being used, what kind?

I am curious. Why do we need to ask that AND what difference does it make what PLC is used?

PeterW · Jul 11, 2006

In the UK, the local isolater must be within 1m from the motor (unless its part of a machine with a single isolation).

We're using some nice kit at the moment. The contactor (interlocked with the safety system) and breaker feeds up to 10 conveyors each. The local starter is a sealed klockner moeller unit, with sockets for power, ASi and two 3 wire sensors. The KM unit has a dip swith setting for overload current.

The power and the ASi are all fed from flat cables run in tray, the ASi has the usual clamp connectors for 24V and ASi, whilst the power has a socket that has a base and hinge effect that when screwed together with the flat power cable in between does similar to the ASi, so a cable with a plug at either end is made to size.

The motor is started from the ASi signal.

It makes a very compact and tidy installation.

rdrast · Jul 11, 2006

RSDoran, Just needed to clarify for a couple reasons..
--If you are only 10 feet away, there isn't a whole lot you can do about cabling costs.
--If using a Siemens PLC, then a remote Profibus combination starter would be the way to go.
--If AB, then a DeviceNet starter would be the way
--If XYZ, then some other network might be better.

Also, if it's just one motor, then any network is probably additional cost, but if it is several, networks might be the best.

Just "I want to reduce cabling costs" is not enough information to respond to in any meaningful way.

rsdoran · Jul 11, 2006

Just "I want to reduce cabling costs" is not enough information to respond to in any meaningful way.

I agree wholeheartedly with that statement.

BUT

I disagree that DNET is the best option for AB and Profibus for Siemens, it all depends on the situation.

The cabling issue is also a "it depends" situation, it all depends on the number of I/O whether a bus communication system is warranted.

JohnW · Jul 11, 2006

PeterW said:
In the UK, the local isolater must be within 1m from the motor (unless its part of a machine with a single isolation).

Where does this come from? In MCCs the "fault free zone" is 3m and we routinely have up to 20m between local isolator and pumps. We often have 300m from starter to local isolator.

VSDs in form 4 MCCs or a single form 1 panel do not as a rule have a local isolator due to the hazard of open circuit with the drive running and EMC issues with local isolator connections.

ramrap.r · Jul 12, 2006

Thanks RSdoran for your reply.

Plc we are using is AB Contrologix with controlnet. But cost of Devicenet is higher then the total cabling cost. Also the distance between PLC & MCC is almost 50 meter & We want to hook up nearly 50 Staters.

So I want any open architecture solution which really can save someting & will be less time consuming.

Thanks once again

rsdoran said:
I agree wholeheartedly with that statement.

BUT

I disagree that DNET is the best option for AB and Profibus for Siemens, it all depends on the situation.

The cabling issue is also a "it depends" situation, it all depends on the number of I/O whether a bus communication system is warranted.

JohnW · Jul 12, 2006

Probably your best solution is to use remote i/o. Fit the remote i/o modules in the MCC and hard wire to that from each starter. Or use an intelligent starter system like the ABB UMC22 or AB E3+ or Siemens Profibus. Or if the Starters are in a form 2 MCC a good solution is Telemecanique Tesys-U with parrallel connections to a comms module for profibus. Also the siemens Simocode Pro if you have individual starter sections.

Even so 50 metres isn't that far to use multi-core cables. It would require 5 x 50 cores.

You have to offset cable installation time and cost against the extra hardware cost of remote i/o or smart starters and a comms network.

We find that using smart starters reduces MCC build time by about 60% but the hardware costs are much higher. Our customers generally use smart starters where they require additional control and/or data from a machine.

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