PowerFlex 70 digital input issue

Hi,

I have a PowerFlex 70 that I have digital inputs one and two configured for Start and Stop-CF respectively.

When I have bring the Start input high and the stop low, there is a stop asserted from the digital inputs on the VFD. When I bring the start input low and the stop input high the stop asserted goes away and the drive is shown as stopped but ready.

I am already controlling the VFD through a 20-Comm-E so I know it works.

Why is my start input causing a stop to be asserted at the VFD?

The default configuration of the Digital Inputs on a PowerFlex 70 is:

Input 1 = Stop/Clear Faults
Input 2 = Start

The "Stop/Clear Faults" function on the discrete input terminal functions as reverse logic. When the input is low, the discrete input asserts a Stop command.

See the example on page 1-13 of the PowerFlex 70 User Manual for the default "3-wire" start/stop wiring circuit.

I have to remind myself of this when I am also using a network interface, because the network interface asserts a stop when the Stop bit is 1.

Ah ha!

Thanks a ton. I'm so use to networking drives that I never bothered to notice the reverse logic on the stop command.

You rock.