I need to wire two vfds at a distance of 800ft. I need to wire two shielded cables (4-20ma) and to control signals. I am planing to hardwire both vfds in two separate conduits, one for analog and one for discrete signal. How the distance can affect the signal? Should I increase the cable gauge? Should I use another wiring method (telemetry etc...)?
Wiring VFDS
- Thread starter Abe5gt
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cadpoint
Senior Member
- Location
- Durham, NC
So after I fill all the required fields and calculate the voltage drop. How do I know which wire to use?
cadpoint
Senior Member
- Location
- Durham, NC
I reckon you contact the sale engineer of the contactor your going to trip and ask the engineer what the contactor can tolerate for voltage drop and still function? Then re-figure!
ptonsparky
Tom
- Occupation
- EC - retired
FWIW, I have used #12 out to a SSR. The relay operated at 5-30 DC. I was at 600` but pivot guys go 1300+.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
BTW I hope the 800' isn't from the VFD to the motor. The reflected wave will be horrible.
http://www.yaskawa.com/site/dmdrive.nsf/link2/MNEN-5JFQPL/$file/AR.AFD.05.pdfhttp://www.yaskawa.com/site/dmdrive.nsf/link2/MNEN-5JFQPL/$file/AR.AFD.05.pdf
ptonsparky
Tom
- Occupation
- EC - retired
Yes the control station
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
You might be better off running ethernet out there instead of 4-20mA. A FO line won't care much about 800 feet. There might even be ethernet out there already that you can use. WiFi or radio ethernet is an option.
- Location
- Bremerton, Washington
For the 4-20 mA portion, its a matter of ohms law - what the total loop resistance is, and the voltage of the power supply. Each device (VFD, panelmeter) is typically 250 ohms in series.
There should be chart showing power supply voltage vs distance. Its a series circuit and voltage drop is typically not an issue unless you are going thousands of feet. 18-2 or 16-2 STP should be fine. Ground the shield only at the power supply end. I would use PLTC or TC
There should be chart showing power supply voltage vs distance. Its a series circuit and voltage drop is typically not an issue unless you are going thousands of feet. 18-2 or 16-2 STP should be fine. Ground the shield only at the power supply end. I would use PLTC or TC
- Location
- Bremerton, Washington
Voltage drop on 4-20 mA is typically not a concern. You first get the total loop resistance, each device is typically 250 ohms. Then maximum distance is determined by the power supply voltage, typically 24 VDC. Then get the resistance of the wire for the distance. You'll find that with 4-20 mA you can go a thousand feet easy with 18 gage. I normally use 18-2 STP. Bond the shield at the power supply end only.
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