I am on holidays here and working on drawings for my students. The particular item is for the student to create a wiring diagram from supplied schematic. As I was creating both some questions arose as to how to create a correct schematic for the students to use. I am looking for someone to show me their version of a single start/stop circuit with two motors. Both motors 1 start when the start button is pushed but when the stop button is pushed motor 1 stops right away but motor two continues to run for a few seconds more making use of a TDOD.
It was while I was creating the answer key/completed wiring diagram that I had some concerns/questions about a correct schematic. I am using Visio to create these and not sure that I can put them here for you to view.
Thanks for any info.

GerryB;

Welcome to ECN!!!

I can compile a drawing per the functions outlined in your message, and post it here later.
It is a simple drawing, so look for the posted drawing sometime tomorrow.



You will need to convert the Visio drawing file to a common graphical file type, in order to post the drawing.
Usable common file types include .GIF, .JPG, and .PNG - color and gray scale.

See if your version of Visio allows for a "Direct" file save in one of the Three above file types. Otherwise, use the "Export" command, and export in one of the above Graphic (Raster) file types.

If you have further questions, feel free to reply by either of these options:

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• E-mail to support@setelectric.net

Scott

GerryB;

Attached to this Thread is a simple Schematic, per your criteria.

Schematic of: Start / Stop AC Motor Control, for Two (2) 3 Phase Induction Motors.

To keep things simple, I compiled the drawing as described below:

1. Both Motors fed from One (1) 3 Phase 3 Wire Circuit,
2. Single Disconnect Switch for both Motors,
3. Control Circuit at "LINE" Voltage,
4. Motor Overload Relays (at control circuit) are separate through that Motor's Starter Circuit,
5. Motor Starters do not include Auxiliary Contacts: each Starter is driven from Control Circuit.

Let me know if there are any questions or comments.

Scott

p.s. If you would prefer to obtain the Schematic "At Original Size", or in another file format, contact me via the contact options listed in the previous reply message.

Just 2 safety and practical considerations:
1.) The circuit above would likely need 2 additional fuses going to the control ladder. The top 3 are sized for the motor load and wiring. The 2 additional would be sized for the relay and contactor coil loads and the smaller control wiring.
2.)TDRs that delay release tend to be very expensive (and large) vacuum Agastats. It would be more practical to use one of the 11 pin octal style relays purpose built or switchable to delay release. In that case, pins 2 and 10 would be across the ladder and and the CR1 contact would go to the control pins of TDO.
Joe

Nice catch!

I concur with Joe, per the suggestion of using the Octal Style Relay, and to include Fuses in the Control Circuit.

Scott

Just to be picky:

Almost no overload relay produced in the past 30yrs has (3)individual contacts for the control circuit. Most manufacturers drawings show only one.

I would use the more generic term 'electronic' timing relay instead of an 'octal' style. Becareful with your timing relay terminals, not all allow you to bring 'line voltage' to the off-delay timing 'control' contact.

I assume this is a 240V or 208V system, 480V control circuits are no longer favored by most industry standards.

I also just use 1, N.C. contact with "OLS" above it to show the overload contact.

Personally, I don't like to use ladders above 120VAC. Looking at Newark's online catalog, they show 32 timers that work at a coil voltage of 120VAC. (Only 1 at 208VAC) Digging further, Magnecraft makes a, TDRSRXP-120V 11-pin octal style that Newark sells for $35.02 and a TDRSRXB-120V rectangular base for $47.37. In contrast, the only Agastat that they show is >$400. That was the point that I was trying to make. The CR1 contact of the modified circuit would be a dry contact across pins 5 & 6 on the octal base and pins 2 & 5 of the rectangular base relay. The relay would be set to the "D" function and there is a broad delay range from milliseconds to hours, set via dipswitches.
Joe