Command Loss and Maintain Motor Operation

Command Loss and Maintain Motor Operation

Application Description

In the case where the VFD speed command reference is lost, there may be applications that require the motor to operate at a certain speed.  In other instances the motor may need to be brought to a stop.  Within the Command Loss function, there are two ways to stop the motor; including cast to stop and decel to stop.  In this Application Note we will look at how to keep the motor operating if there is a command loss.  In the LSIS VFDs the speed reference is set by the parameter named Frequency Command.  It can be the Keypad, Digital Input, Communications (RS485), or the Analog Input.


Setup/Programming Required
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The programming for the G100, S100, H100, and iS7 are all very similar.  It involves programming the Command Loss parameter and the Lost Preset Frequency.  

Setup/Programming Process

G100, S100, H100 & iS7:

Protection Group (PRT/Pr)
Set PRT 12 (Lost Cmd Mode) to 5 (Lost Preset).
Set PRT 14 (Lost Preset Frequency) to the desired frequency to operate the motor at if there is a command loss.


 C100:

When using the C100 there are several steps used to allow the drive to do the same thing.  This is due to the C100 only allowing the drive to stop the motor within the Command Loss parameter.
       Main Command Source:
  1. Set the digital input P3 to 22 (2nd Source).
  2. The freq control source must also send a signal to the drive’s P2 input.
  3. Set drv2 to Fx/Rx1 (must jumper P1 to CM, this is hard wired Run command)
  4. Set Frq2 to V1 (0-10V) or any other value (in this case the drive would be getting the Cmd Source from the V1 analog input)  

      Command Loss Control:
  1. Set drv to Fx/Rx1 (same as Drv2)
  2. Set Frq to Keypad
  3. Program the keypad frequency command to the value needed to run when the V1 and P3 signal are lost.  Do this when P3 is not activated.
NOTE: When setting up the C100 to operate this way, the drive will not recognize a command loss, it will just switch from the drv2 source to the Keypad (drv source).  The only way the drive will perform this way is if it loses the P3 (2nd Source DI signal).