Accel. time on POWERFLEX

Hi,

I would like to know if the parameter #140 (Accel time) on a Powerflex drive can be used to control a kind of timing.

for exemple : I have an exquipement running at 40Hz. Can I set the Accel time to 2 sec and if a I change the speed for 60Hz the real Accel time will be 2sec.? (I mean from 0Hz to final speed)

Thanks
Martin.

in short the explaination you provided is correct the accel time is use to control the rate of ramping

On the PowerFlex drives, when you set the accelleration time, you are setting the number of seconds that it takes to go from zero speed to whatever maximum speed the drive is programmed for (usually 60hz). This defines the slope of the ramp.

As a result, if you are going from zero to 30hz, or from 10hz to 40hz, or from 30hz to 60hz, since the speed change is 30hz in each case, the time to make that change will be one half of the accel time setting (assuming 60hz for maximum speed). From 40hz to 60hz would be one-third of the accel time under the same max speed settings.

Martin,

From experience, a 2-second acceleration time would be very fast for most motors and loads. 5 to 10 seconds acceleration time is a more achievable range to prevent current trips. Your situation may be different, though.

Ok fine.

If I have to motors both with 60Hz of max speed, if I press stop on myy panel view, do the motors are goign to stop exactly at the same time? (with the same decel. rate). the motors are not the same size.

thanks
Martin.

If both drives are programmed with the same decel ramp time, and both are going the same speed before stopping, and neither exceeds its braking capacity when slowing down, and both drives are programmed for "Ramp to Stop", then the stop time will be the same regardless of size.

DickDV said:

If both drives are programmed with the same decel ramp time, and both are going the same speed before stopping, and neither exceeds its braking capacity when slowing down, and both drives are programmed for "Ramp to Stop", then the stop time will be the same regardless of size.

Click to expand...

I 2nd this one.

Though, i do have a feeling that he is trying to create a cheap "Positioning" system by using VFDs instead of servos.
As in "Timing"??

MGuenette said:

Ok fine.

If I have to motors both with 60Hz of max speed, if I press stop on myy panel view, do the motors are goign to stop exactly at the same time? (with the same decel. rate). the motors are not the same size.

thanks
Martin.

Click to expand...

It depends. Your VFDs may shut off output at same time, but
it doesn't mean your motors will stop same time.
"Ramp to Hold" might work better.But again it's not guaranteed.