Motor Operation in the Plant

You should read the operation manual before attempting to operate any control system....You will find there are optional set up configurations to suit your needs and preferences....check with the distributor for any clarification needed...

http://ecatalog.weg.net/files/wegnet/10-17346.pdf

Thanks for your mention but it is not what I want to know.

Detail condition is as below;

a. DOL

b. Motor starter is composed with M.C., MCCB, TOL and ZCT

c. Control mode: Local (field), Remote (DCS)

d. LCS has Local-Remote Selector switch and Start/Stop push buttons

The point is whether the motor stopp or still run during the position change of Local <--> Remote at the LCS.

Thanks.

If there is a contactor involved in the DOL starter, a changeover action will trip the starter and the motor will stop. No two ways about it.

Thanks your reply.

I think so too. But in operation view, an operator makes motor run with 'LOCAL' mode and if he wants to change the operation mode from 'LOCAL' to 'REMOTE', should he stop motor and start/run it again in 'REMOTE' condition?.

I've no idea for it.

Normally yes, you would need to restart. However, if it is very important that the motor must not stop during the changeover from Local to Remote, you must use a "make-before-break' switch as has been mentioned by Tornado. Some care needs to be taken to ensure the continuity of supply to the contactor coil. For example, bith local and remote controls are ON for a short while (the overlap time) which is human-dependent.

Ideally the only thing that your LCS (Local Control Station) should change is the source (L/R, Local or Remote) of the contact closures that tells the motor to start, run, or stop, but a lot depends upon the sophistication of the overall control system.

The speed at which the L/R switch is operated should have no effect on the outcome, as a matter of good design switches for that purpose are very fast acting and do not allow for indeterminate state transitions. If you have a chance look behind the panel at those selector switches (not when the panel is energized!) to see how robustly they are built to prevent "teasing" by an operator.

You will have to look beyond the switch to the control circuitry to see what course of action a change of state will initiate.

I would get some who knows!!!! to look at the associated Electrical Drawings for the control circuit and see if the motor is running it is latched in by its own or start Pilot relay indepent to the select switch.

I would also look and see if the Selector switch effects Power to this Pilot relay. If it does you are in Guess territory i.e will the coil drop or hold or not.

If it has been design weirdly you might also check if it drops power or is on the shunt trip to the circuit breaker???? Very unlikely and a very poor design.

Check the PLC to see if there are any interlocks the control switch is wired to that might feedback.

In other words get someone to check the electrical drawings, You have not provided enough information to give you a answer

I am attaching the one sample circuit.

I am understanding my concern is the practical matter.

Hope to see you guys good feed back.

Thanks.

It would appear from your diagram that the remote is a simple on off switch rather than a momentary push button. If this is the case, then it will work but with serious reservations as you will have negated one of the primary advantages of a DOL starter which is "no volt" protection.

If it is a momentary type, then the circuit won't work correctly as the button would have to be held actuated. It may be some form of process control, but "no volt" concerns may still be an issue.

The big problem that I see with the circuit (assuming the remote is an on-off switch) is that in a case where the C/O switch is in the remote condition, whilst the motor can be stopped via the Off, fault or E-stop contacts opening, it would immediately restart upon their re-closing, and that could be highly dangerous, particularly if the fault contact is a thermal overload which could reset without notice.

With that circuit, the contactor will release upon operating the C/O switch. Although it is possible to operate them quickly enough to beat the coil drop-out, it's not recommended design practice.

I don't see that circuit as being best design practice, and is possibly highly dangerous as described above.

It will depend on whether the Local/Remote switch is make-before-break versus make-after-break, whether you press the "On" button while making the switchover, and perhaps other details.

By the drawing of the circuit you provided your remote will not function as desired. The hold relay will not provide power to the coil when switched to remote position.

Not knowing the application not sure of the safety aspects of this change. A lot of times local start up can be to ensure safety of plant personnel.

With personnel safety in mind you may not be able to stop the motor with the selector switch as wired.

Do a proper remote with a start and a stop. And before change please review all aspects of personnel safety. If you can't see the motor and all aspects of motion the motor will engage. Then you can't see the personnel in the way.

At least with a stop button you can stop it if you hear them scream!

Most likely why the Line-of-Sight rule was put in place in the US.

Also, the nature of the motor load is not given.

He has used the wrong symbols in the diagram but it looks like he is trying to latch the ON switch using the NO contacts of the "88" coil.

If this is really what you have.....

If you don't want the contactor to drop and stop the motor when you change from remote to local, hold the local "on" button in when you flick the switch.

it depends on your control design and motor location local option is only installed where is need of visual presence (to check the all-clear) and if it is the in-process serial sequence so the dcs will monitor the back forth sequence to be in appropriate position.

but in some places/plants must you have to start the motor in local mode and then hand it over to automation .