11 replies to this topic

[chaterpilar]

Hi !!

What is the maximum distance ( cable length) allowed between a 100 Hp motor and its Variable speed drive...?

I want to locate the VSD panel based on this info.

Any thoughts....

Chaterpilar

[Gigger]

Hi !!

What is the maximum distance ( cable length) allowed between a 100 Hp motor and its Variable speed drive...?

I want to locate the VSD panel based on this info.

Any thoughts....

Chaterpilar

Hello Chaterpilar,

Most VSDs I have worked with allow for a cable length of 150meters if screened cable, or 300meters if unscreened cable between the VSD and motor.If a greater length is required install a output choke.

Hope this is of some help.

Gigger

[mariomaggi]

Dear Chaterpillar,
I've had some bad experiences with long lines.
I cannot recommend a general lenght for all types of inverters and for all voltages and power ranges and type of final load.
Also the motor insulation is important, in certain conditions, when voltage reflections are possible.
Regards
Mario

[jOmega]

Chaterpillar,

Each case must stand on its own merits. There is no Rule of Thumb that can be applied to all situations; not even to most situations. Each one must be examined on its own. Parameters for every case are different.

If you must have a general rule..... I don't think you could go too far wrong with keeping the motor within a meter or two of the VFD. Otherwise ..... you could add a dV/dt (dU/dt) filter at the output of the VFD. Filter connets to VFD output terminations ..... motor connects to filter terminations provided thereon.

See my post of October 1, 2006 to Boby ..... Speed Control of Slip Ring Induction Motor Using Vfd for information on such filters.

Kind regards,

jΩ

p.s. Don't forget to give consideration to IR drop in wires going out to the motor..... Voltage lost in wire run means less voltage at motor terminals....

[kens]

Chaterpillar, each drive manufacturer will state max cable length for each of their drives. Their can be a large difference in capabilities in this area. Depending on where you are situated there may be other requirements regarding RFI. The cable lengths that are allowable with regard to RFI are often shorter than the maximum allowable. This is very dependant on the local regulations. I agree with jOmega, you cant go wrong having the drive within a few meters of the motor.
Ken

[jOmega]

Chaterpillar,

Came upon this article in my library that is written by the folks at Yaskawa Drives.

Think you'll find it informative.

Kind regards,
jΩ

AC Drive/Motor Long lead Issues

[chaterpilar]

Thanks everybody for the inputs.

Chaterpilar

[jraef]

Chaterpillar,

Came upon this article in my library that is written by the folks at Yaskawa Drives.

Think you'll find it informative.

Kind regards,
jΩ

AC Drive/Motor Long lead Issues

Excellent paper, thanks jΩ.
I have similar papers provided by reactor manufacturers and they have an obvious bias towards selling more reactors. This paper seems to use a more balanced approach. What I particularly liked was confirmation of my own history with this issue, that being the initial recommendations of 300 feet, then later 150 ft., then 50 ft., now 25 ft. as the maximum without mitigation of some sort. I see know where all this was coming from. 300 ft. came from the days of Darlingtons, 150 ft. must have been the "best case scenario" promoted by salesmen when IGBTs first came out, 50 ft. was likely the correction insisted upon by the engineering departments because that was where a reflected wave COLUD start, now 25 ft. is the conservative number to be sure that there is no reflected wave regardless of other conditions. Makes sense to me now.

I have been seeing recent accounts of newer IGBT switching technologies that purport to allow longer lead lengths without additional mitigation. I am skeptical, but if I can find something in writing I will share it here. They came from salesmen, so if I apply that experience noted above to these new claims, I would suspect a reduction factor of 88% is in order!

[jOmega]

I have been seeing recent accounts of newer IGBT switching technologies that purport to allow longer lead lengths without additional mitigation. I am skeptical, but if I can find something in writing I will share it here. They came from salesmen, so if I apply that experience noted above to these new claims, I would suspect a reduction factor of 88% is in order!

JR,

Per chance, are you referring to "Soft Switching" ????

[jraef]

Yes. Schneider is one manufacturer who has gone on and on about it.

[jOmega]

Yes. Schneider is one manufacturer who has gone on and on about it.

Danfoss has had it in the VLT 5000/6000/8000 products up thru 7-1/2 hp since back in the late 90's

Doing some research on it as I recall an IEEE ISA journal piece on the subject some time ago and am looking for it . Hope to have some more to say in the near future and will post in a separate thread.

[jOmega]

JR ...

see new thread on Soft Switching.