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What does NST mean on Altivar drives?

Published date: 07 May 2019

Issue: 
What does NST mean on Altivar drives?

Product Line:
All Altivar drives

Environment:
All

Cause:
NST is not a fault but rather a status indicating the drive is in a freewheel stop condition.

Resolution:
Causes and fixes :
 
The drive is in 2 wire control (TCC = 2C) and was powered up with an active run command.
Cycle the run command or set TCT to LEL. (IO menu, 2 wire type = level)

The drive has an input assigned to Freewheel stop, NST. 
The input needs to be active.

The drive is in 3 wire control (TCC =3C). 
LI1 must be active before the NST will clear.

The drive is being controlled by serial communication, and drive is not receiving the proper command signal. 
The drive will display NST until the correct value has been written to the command word.

A loss of a 4-20mA signal is programmed to freewheel stop. 
When the input is lost, status goes to NST. Verify the 4-20 mA signal.

The drive is in terminal control, and the STOP button on the integral or remote keypad was pressed.
While in terminal control, the STOP button functions as an E-STOP.  If the keypad STOP button is pressed, the drive will go to NST (excluding the ATV212, which will display a flashing "E"). Power cycle the drive to clear the NST.

For the ATV61/71 VFD only: If the drive is running, and the voltage applied to the PWR input terminal drops below +19Vdc, the drive will stop and display NST. 
You will need to make sure you close the +24 VDC to PWR input and cycle off and on the run command again. Make sure the factory-installed jumper between +24 and PWR is connected firmly. Or if a safety circuit is connected to these terminals, be sure the circuit is closed.  

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