×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Long leads between VFD and motors
6

Long leads between VFD and motors

Long leads between VFD and motors

(OP)
Application: 300 ft + of cable run between a 460v VFD and a 1/8hp gearmotor. 2 of each gearmotor and drive powering a mobile device. Obviously, motor protection, such as a line reactor is required. But, do they have to be located next to the motor? Are there any new, smaller devices out there? The mobile device is small and real estate is at a premium.

Any suggestions?

RE: Long leads between VFD and motors

I would think that you could put the small dv/dt capacitors/damping resistors at the motor and the line inductors at the VFD.

RE: Long leads between VFD and motors

2
1/8hp?  I'd consider going 240v instead of 480, then all those problems dissappear. . . .

Voltage drop probably wouldn't even be a problem for a motor that small (might want to double-check that though).

RE: Long leads between VFD and motors

If you are using un-shielded cable, then 300ft(100M) is usually ok without an output reactor. I would check with the VFD manufacturer and ask them. As peebee says, might be worth going 240v then the peak-peak volts is reduced and, assuming your motor is wound 240-460V (delta-Y), then this motor would have greater protection. Where volt drop is concerned, as your application is driven via a gear motor it is likley constant torque, so ensure your cable diameter is adequate to cope with any potential volt drop otherwise running at slower speeds may not have the torque needed, especially 1/8hp.

RE: Long leads between VFD and motors

peebee has an excellent suggestion, one that I've used for these small motors numerous times with great success.  A single transformer take 460V down to 230V to feed both drives will likely weigh less that the two reactors you would need at 460V.

If you decide to use reactors, place them next to the drive.  They protect the motor equally well anywhere in the motor leads but, next to the drive, the protect better against ground pulse currents.

RE: Long leads between VFD and motors

I agree with Peebee proposition. Lowering the voltage will improve the motor insulation withstanding spikes. The motor must be reconnected for 230 Volts.

RE: Long leads between VFD and motors

Check latter portion of recent thread "Using Explosion Proof Motor on Distorted Supplies" on this site re the issue of VFDs and long cable lengths.

As you will read sinus output filter are better than simple output reactors depending on the type (and carrier frequency) of the inverter.

The explanation is too long to give again here.

Hope it helps.

ICEMAN

RE: Long leads between VFD and motors

Sinus output filter?  Sounds like a Kleenex!  ;-P

RE: Long leads between VFD and motors

Have you considered using a reflected wave trap?  I've used the Cutler-Hammer RWT with success in the past.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources