Control stop/start motor with ramp

Hello guys, i would like to know if is possible keep always active the run command in a vf drive and for stopping the motor only send 0 reference. It´s possible??? because I want to program a ramp function in my plc for start and stop one motor. could someone tell me how to do this type of control please?.

What PLC?

I would still use start/stop though when command is at 0 speed.

Yes it is possible to stop a motor by sending a 0 speed setpoint, but it is not reccomended that you do that. Always isssue a real STOP command (because the 0 speed point can drift around). You can still use ramp functions, one to ramp up to set speed, and another to ramp down to 0 speed, where your PLC program then disables the RUN command (same as STOP on most VFDs).

A quick way to set a straight-line start ramp is to set the acceleration time in the VFD. For example, if you want your motor to start at 0 and ramp to full speed in 10 seconds, then set the Acceleration Time parameter to 10 seconds. There is a similar setting for Deceleration Time.

If your Start and Stop ramps are not linear, then you probably would need to set up a ramping routine in your PLC program (although many VFDS now have built-in non-linear ramp functions).

There are times that you want your motor to stop moving but still be in control and yes, you can do this. There are certainly other needs/situations that still require you to stop the drive run command.

Your drive setup needs to factor into the discussion as well.

If the drive is setup in Flux Vector Mode (encoder required), then it will hold position when you command it to zero.

If the drive is setup in V/Hz mode, then it will stop making the motor move, but will not hold position when you command it to zero (gravity or other forces may cause movement). So you are not really in control.

If the drive is setup in Sensorless Vector Mode, you may have issues at zero speed. My experience with sensorless vector mode is that drives often creep at zero command speed.

As for the ramp up/down, see Lancie1 reply.

also if held at zero speed for long times use an external cooling fan on the motor so it does not cook