question for VFD control

hi guys

I am working on setting up a MCC for some of VFDs. my question is how to take care about Harmonic filter? under what condition we must use them, and under what condition it is not really necessary.

thanks

you typically don't use filters for 240 volts.
for higher voltages you have line and load filters.
the line filters depend on what is in the plant, line voltage (clean vs dirty), surges, welders in the plant? the load filters depends on the application and the distance from the vfd to the motor.

you should contact your drive distributor in your area for his recommendations. may cost you more to install, but voided warranties due to improper installation is more costly.

regards,
james

thanks Jam

the distance between VFD and motor is less than 200', do we still need load filter?

Keep in mind that line reactors are primarily meant to keep drive harmonics from reaching other plant equipment, not to protect the drive. Load reactors are useful for long motor runs, especially on larger motors. 200' is pretty long.

Motor leads of 200 feet become a problem for motors under about 100hp at 460V. The lower the hp, the shorter the leads can be before needing at least a 3% load reactor. For example, if you have a 5hp motor, the problem is so severe that a load reactor is not enough. You would need at least a dv/dt filter and maybe more. At 50hp, the reactor would be enough.

As to input filters, first check to see if your brand and model of drive already has one. If not, then you must do a harmonic analysis to determine what your power network harmonic content will be. If above the specs of IEEE519, you will want to start adding filters.

depending on the manufacturer, you have the following.
0 to 50 ft - no problem.
50-75 ft is the gray area.
past that, you can line / load reactors.
you can also use speciality cable to reduce the harmonics.

dont forget one thing, common motors run at 57-63 hz, i alvays specify inverter rated motors. their more expensive, but at more than 60 hz +/- 7%, regular motors heat up and tend to burn out.
regards,
james

James Mcquade said:

dont forget one thing, common motors run at 57-63 hz, i alvays specify inverter rated motors. their more expensive, but at more than 60 hz +/- 7%, regular motors heat up and tend to burn out.
regards,
james

Click to expand...

Most inverter rated motors we have are much higher than that. On their name plate they have 90hzrating and some have a 200Hz rating. Is 60Hz +/- 7% even considered inverter duty?

I think Mr. Macquade is being much too conservative. Commodity motors with Class F insulation are used on inverters at 480V frequently and successfully. The motor manufacturers' sales manuals typically show torque-speed curves from 15hz to 90hz.

Inverter duty motors generally go beyond that range and will have an MG1P31 indorsement of the insulation.

My experience:

- Many manufacturer's "standard" motors are inverter duty nowadays
- The price premium for inverter duty motors has dropped
- Old motors with 1.15 SF and Class F insulation generally work without problems on VFDs
- Filters and "clean power" tend to be overspecified
- Proper grounding of all equipment is very important for harmonics and preventing bearing fluting
- Check your total length of wiring between the motor and drive against the VFD supplier's reccomendations for the hp being used
- The mitigation devices employed fall into two categories: Line side and load side of the VFD
- Most good VFDs have input reactors as standard
- So-called "clean power" VFDs don't protect the motor, but are intended to reduce line side harmonics and effects on other equipment and customers
- If you are concerned about motor dV/dt damage Reflective Wave Traps may be cost effective protection
- If the VFDs are a small percentage of total plant power consumption line side harmonics are probably not a problem. If you are unsure, most VFD suppliers will provide a harmonic analysis at no cost
- Active front ends for line side harmonics protection are becoming more cost effective than 18-pulse and older technologies

Tom Jenkins said:

- Active front ends for line side harmonics protection are becoming more cost effective than 18-pulse and older technologies

Click to expand...

Have any of you looked into these:

http://www.google.com/search?q=yask...sugexp=chrome,mod=15&sourceid=chrome&ie=UTF-8

Oh, and this thread gets my golden nugget award (search filter).

OkiePC said:

Have any of you looked into these:

Click to expand...

Interesting. I believe ABB has something similar?

The only thing is, since Yaskawa makes drives in Houston, you'd think they could find a native English speaker to check their presentations! (I know - I'm being picky, but really .....)

Tom Jenkins said:

The only thing is, since Yaskawa makes drives in Houston, you'd think they could find a native English speaker to check their presentations! (I know - I'm being picky, but really .....)

Click to expand...

Do they speak English in Texas?