VFD modelling in SKM

[lielec11]

I am trying to coordinate a breaker with a motor starting curve except the circuit breaker the contractor is using doesn't fall below the hot stall point on the TCC. However, this is assuming the motor is starting across the line. In reality it will be connected to a VFD.

1) Is there a way to model this?

2) If not, do I need to show the hot stall point at all when showing motor protection by a circuit breaker?

 

[Bugman1400]

Would like to know the specs for the breaker, motor, VFD, and source imp.....or the SKM model, if you have that.

 

[mayanees]

I am trying to coordinate a breaker with a motor starting curve except the circuit breaker the contractor is using doesn't fall below the hot stall point on the TCC. However, this is assuming the motor is starting across the line. In reality it will be connected to a VFD.

1) Is there a way to model this?

2) If not, do I need to show the hot stall point at all when showing motor protection by a circuit breaker?

Put the motor on a TCC, then from the component editor uncheck the automatic links and modify the TCC starting curve parameters using any of the available starting means. Using a full voltage start with 150% inrush replicates a current-limited VFD start.
I would've said contact SKM but their Customer Support is feeling the pinch of downsizing, or overgrowth, in my opinion.

Sounds like you're getting work!
.. continued success!

 

[lielec11]

Put the motor on a TCC, then from the component editor uncheck the automatic links and modify the TCC starting curve parameters using any of the available starting means. Using a full voltage start with 150% inrush replicates a current-limited VFD start.
I would've said contact SKM but their Customer Support is feeling the pinch of downsizing, or overgrowth, in my opinion.

Sounds like you're getting work!
.. continued success!

Things have been moving slowly but work is work. Anyway, wouldn't increasing the inrush to 150% shift my starting curve all the way to the right, making it extremely hard to coordinate with? How do this mimic a VFD start? VFD typically ramps up slowly...

 

[mayanees]

The typical across-the-line starting curve shows an inrush of 5.9 in the TCC starting curve tab while in the component editor. Uncheck the "link inrush with LRA/FLA and use a value of 1.XX which represents 1XX% current limiting. Use whatever your VFD is limiting the starting current to. Soft-starts are typically a 150-200% of fla limiter.
You can also do it with the TMS/I*SIM defaults tab in the motor component editor, but you would need to select a load and starter from the library. Then you could use a solid-state current ramp at whatever magnitude you desire.
Probably easier just modifying the across-the-line curve though.

 

[lielec11]

The typical across-the-line starting curve shows an inrush of 5.9 in the TCC starting curve tab while in the component editor. Uncheck the "link inrush with LRA/FLA and use a value of 1.XX which represents 1XX% current limiting. Use whatever your VFD is limiting the starting current to. Soft-starts are typically a 150-200% of fla limiter.
You can also do it with the TMS/I*SIM defaults tab in the motor component editor, but you would need to select a load and starter from the library. Then you could use a solid-state current ramp at whatever magnitude you desire.
Probably easier just modifying the across-the-line curve though.

nvm i just had a brain fart. i typed in 150, which is actually 1500% This curve looks more appealing at 1.5! Thanks!