Freaky freaq drives

[dadeo]

GOT a weird one I do. got 3 1336 AB drives controlling three 15 hp motors with 120 volt input cars in them . motors about 200 ft from drives. Three wire stop starts. Control wires and load wires ran in same pipe. The problem is when more then one drive is turned on they don't stop.getting 30 to 52 volts back on the start wire keeping the drive running. meggered all wires and motors all clear.feel there is a voltage induced in the conducters.I know control wires should be in a separate pipe or even shielded cable .BUT why now? told this was like this for yrs . WHAT CHANGED ?????

 

[petersonra]

Re: Freaky freaq drives

in a 3 wire configuration the voltage on the start terminal is not what turns off the drive.

it is the lack of voltage on the stop terminal that truns it off.

 

[dadeo]

Re: Freaky freaq drives

MOMENTARY POWER ON THE START STARTS THE DRIVE . ANY LOSS OF POWER ON THE STOP DROPS IT OUT. just like a stop start on a mag starter THANK YOU

 

[petersonra]

Re: Freaky freaq drives

maybe a dropping resistor on the stop terminal.

 

[dadeo]

Re: Freaky freaq drives

Ty we thought of that and thought about using shielded cable but because of the leanth of the run and the amount of bends probably easier to run seperate pipe for the control wires

 

[ron]

Re: Freaky freaq drives

I don't know the answer, but 200' from the drive to the motor seems very long. Most VFD manufacturers that I've talked with suggest approx 100' max unless you install mitigating filters for reflected wave harmonics. The lead length depends on the voltage and operating frequency of the transistors.
http://www.yaskawa.com/site/DMDrive.nsf/applicationData/AD4079/$File/AD4079.pdf#search='vfd%20harmonic%20long%20lead'

 

[dadeo]

Re: Freaky freaq drives

Ron ty for the link . I have heard the term ringing but didn't really get it thought it was if you put the line and the load wires in the same pipe this explains it well ty funny how this was running for yrs lol or was it?????? thanks again

 

[masterinbama]

Re: Freaky freaq drives

AB recommends sheilded cable on the motor leads on long runs.If you are using the terminals on the drive without an isolation relay then your control voltage is 30v dc from the drives internal dc buss.It doesn't take much current on your motor leads to induce this much voltage.Even with sheilded motor leads I have had to put in isolation relays so I could make the control voltage 120 AC.

 

[don_resqcapt19]

Re: Freaky freaq drives

I have seen that before. It takes very little current for the control circuit and you have induced current from the motor leads. I have often used the same installation as that and most of the time, it does not cause any problems. In the few times where it caused problems, I have added a control relay or a pilot light. The pilot relay serves the same purpose as a dropping resistor and is wired in parallel with the control board input. The relays have a higher current requirement then the control boards and also work. The relays are installed at the drive and the field wires control the coil, and the contacts interface with the drive control board.

As far as the motor length requirements, we have well over a 100 drives installed with motor leads over 150'. We do not use filters or reactors or even drive rated motors. We have not experienced any problems. We also use 110 volt controls that are installed in the same raceway as the motor leads. The control wires are #14s and the motor leads are #12 or larger as required by the motor load.

don