For a DOL motor you don't need to show the starter just a circle with the motor number or drive Number e.g. P-101 for pump 101.
For a VFD a box beside the motor with the tag No inside e.g. VSD-101.
We don't usually show any electrical details i.e. Stop/Start buttons or interlocks unless they are something special otherwise it clutters up the drawing. You can show generic motor control on the cover sheet to show typical controls.
P&ID stands for Process & Instrument Diagram (not electrical)
The interlock logic is too complex to show on the P&ID this should be on a separate document
Roy
You can choose how you want to display these things as long as you don't stray from any adopted specs or standards, and display them on a legend sheet so everyone can know what they are.
I agree with Roy that representing these can clutter a drawing, but my current client wants them on their P&IDs.
Their P&IDs will show a VFD or starter as a box, appropriately tagged, with several panel-mounted ISA devices (circles with lines through the middle, aka bubbles or balloons) for each function.
Starter coils themselves usually aren't shown, but if there is a Hand-Off-Auto (HOA) or On-Off switch associated with the starter, it will be shown as a hand switch (HS). Similarly, if there are indicating lamps to show when the motor is running, they will be shown as YL (event, state, or presence, Y, and light L). Some kind of feedback is usually provided to the control system in the form of a YS for an auxiliary contact on the starter or an IS if a current switch is provided.
Since VFDs usually have a start/stop or enable (or both) that can be indicated with one or more HS, as needed. If there is a fault relay, it can be represented by UA (multivariable alarm, since drives typically have more than one fault that will operate the single relay), or YA, since the drive is in a faulted state.
If an external speed reference is sent to the drive, this is indicated with a bubble designator that ends in Y, since it is converting (Y) the signal into speed. The first letter of the loop will be the identifying letter of whatever is being controlled by manipulating the speed (temperature, pressure, flow, etc.). If the measurement transmitter output is sent to the VFD directly so that the speed control is done by a control loop in the VFD itself, a device with a tag that ends in C can be included, e.g., if the fan speed is being used to control pressure from a pressure signal sent directly to the VFD, label the device PC.
My client has defined the standard VFD block for the type of VFD they use and the way they connect it. It always has the same bubbles, and is included on a legend sheet so that everyone always knows what it is. It has four bubbles: a HS for a HOA switch on the VFD cabinet, a HS for the remote Start/Stop signal, a YA for the fault alarm, and *Y for a external speed reference (substitute the process loop variable in for *). Standard starter blocks for MCC buckets have three bubbles: a HS for a HOA switch, a HS for the remote Start/Stop signal, and a IS (current switch) for proof-of-run feedback.
xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
The firm I work for designs plants for large multi-nationals all over the globe.
I looked back at several projects showing the same pump with VFD for different clients. This VFD typically has a manual controller in the DCS.
As you can see by attached we taylor the P&IDs to suit the client. Sometimes we show lots of detail other times not.
As Xnuke says you can really do anything so long as you convey the information. We do a spreadsheet showing all the interlocks.
Regards
Roy
