Need help setting VFD parameters

[k3tchup ch1ps]

I'm trying to get my VFD setup dialed in, and I have a quick question about the motor's ramp times.

I know the acceleration and deceleration parameters are super important for a smooth start and stop, but I'm trying to avoid just punching in random numbers.
Does anyone have a simple formula or a rule of thumb they use to correctly calculate the starting and stopping times for an induction motor? I want to make sure I'm doing it right.

Any help would be great!

 

[waka.chi]

I usually just match the ramp times to the load and let that guide me. Start with something conservative, like 5 to10 seconds on acceleration, then change until it feels smooth without tripping faults. Decel is trickier, go too short and you'll hit overvoltage, so stretch it out unless you've got a brake resistor, hehe
Goodluck

 

[EE_Goodman]

I'm trying to get my VFD setup dialed in, and I have a quick question about the motor's ramp times.

I know the acceleration and deceleration parameters are super important for a smooth start and stop, but I'm trying to avoid just punching in random numbers.
Does anyone have a simple formula or a rule of thumb they use to correctly calculate the starting and stopping times for an induction motor? I want to make sure I'm doing it right.

Any help would be great!

You're right not to just punch in random numbers since that's a good way to trip the drive.
There's no single magic formula here though because the ideal ramp time depends on a bunch of factors which are the motor's inertia, the load's inertia, and the torque required.
A solid starting point is to look at the motor's full-speed run-up time.
You can often find this in the motor's technical data sheet or on the nameplate.
Then a good starting point for your acceleration ramp time is to set it to 2-3 times this value.
As for deceleration, it's more about the application.
If you have a highly inertial load like a flywheel, you'll need a longer ramp time or even a braking resistor to safely dissipate the energy.
A basic starting point is to match the deceleration time to the acceleration time.
Then from there, it's all about observing the motor's performance and tuning.
It's good to make just small increments when you adjust the ramp times up or down until you find the sweet spot where the drive doesn't fault and the motion is controlled and stable.