What is basic troubleshooting procedures for NLP on an ATV61 or ATV71 drive?


17 August 2022

What can I do to resolve NLP on the display of my ATV71 or ATV61 drive?

Product Line:


Drive will not run.

WARNING: the person performing these tests will be exposed to AC Voltage up to 690 VAC and DC voltages up to 1000 VDC.  This should only be performed by a properly trained person while wearing appropriate PPE.  Consult the Product Installation Manual for details before attempting.

Check Line voltage phase to phase on the drive terminals.
Verify if the jumper is connected between PA (+) and PO terminals.  Larger HP drives may have a DC Choke connected between these terminals.
Check the DC bus voltage between PA (+) and PC (-)
Check the DC bus voltage between PO and PC (-)
Go to monitoring 1.2  (Drive Menu) verify mains voltage equals line voltage. 

DC Bus Voltage should be approximately 1.414 times the Line Voltage.
If voltage measurement from PA to PC is not correct, the input bridge of the VFD and the input line power will need to be tested.
If the Voltage measurement between PO and PC does not match the voltage measured between PA and PC there is an open or loose connection with the Jumper or DC Choke.
If the Voltage measurements are correct but the Mains Voltage displayed in the monitoring menu does not match, there may be a loose connection inside the VFD.  This can also be caused by distortion of the input line power called Flat topping.
If the Mains Voltage displayed in the monitoring menu shows "No Measure" power down the drive and verify the ribbon cable connection to the main control board of the drive.  This cable will connect to the Power Board on smaller HP drives and to the Motor Control Board on large HP units.

If NLP remains after confirming good voltage and good connections, the drive will need to be repaired or replaced.

US customers can contact DPSG (Drive Products Support Group) for further assistance at 888-778-2733, option 2 for Technical Support and then option 4 for AC Drives and Softstarts.
Customers in other countries should contact their local Schneider Electric support.