You are 100% correct. You only need to size according to the motor full load current.

If anything you may want to confirm from the choke supplier the overload capability (all chokes have a short time overload capability, same for the vsd) of the choke. Just to confirm the choke's overload capability, coincide with that of the vsd.

Motor rating 3.7KW and Choke ratiing 1.5microH used in conveyor. This conveyor mostly in running condition above 800RPM. Having one problem in choke that is choke get burn smille and inslation comes to week at the time of running. We measure the choke temperature found above 80*C. Last one year we change the 2nos of choke for the same drive..

Plz give rating of the choke for the 3.7KW motor...and mention the maintain details of choke

dear arun babu,

u havent mentioned wheather it is an input or output choke

normally what we manufacture for 3.7kw motor is 3.7kw , 2.22mh input or output choke(saturation level will vary depending upon input or output choke)

Is it possible to specify the saturation levels for a input and output choke? Does it change for different size (current rating) chokes?

This a output choke.. And Maximum load current is 1.2A

Motor rating 3.7KW and Choke ratiing 1.5microH used in conveyor. This conveyor mostly in running condition above 800RPM. Having one problem in choke that is choke get burn smille and inslation comes to week at the time of running. We measure the choke temperature found above 80*C. Last one year we change the 2nos of choke for the same drive..

Plz give rating of the choke for the 3.7KW motor...and mention the maintain details of choke

We need voltage and full load amps for your motor to make intelligent reply.

The reactor should be designed and supplied for VFD applications.

I have had experience with various manufactures. Some make good reactors. Others burn up on the test floor.

Many motors are now designed for VFD supply and do not need reactors, but the reactors are usually kind to the motor. They tend to reduce high frequency components and issues with reflected waves.

Rated Amps 7A and present full load amps 1.2A

Give the reason for choke problem

There are many high frequency components in the output waveform. Depending on the steel used, ventilation, insulation temperature rating, conductor sizing etc, the final temperature rise can be significantly higher than a "60Hz" rating.

The reactors we specifically had problems with were input reactors for 1500HP phase controlled DC drives. Once we got the "bugs" out we tightened our specs for the reactors and subjected new designs and manufacturer's products before qualifying them. Some manufacturers always passed, some routinely failed and were disqualified as a supplier.

For a while we even used air core reactors, and had significant problems with heating the surrounding sheet metal.

Your application requires a minuscule reactor and you should be able to oversize the current rating by 2 or 3 times without a significant cost penalty.

there are many fundas to be understood here . . . .

what are you using the reactor for? as an input choke to the vfd? i presume so.

the L value determines the XL value at your input power frequency (over which you have almost no control).

the XL value determines to volt drop across the choke at the current actually drawn when in operation.

if your drive manufacturer specifies a reactor with 4% volt drop at some current value then you must know that at any other current (determined by the actual load) the volt drop will differ proportionately.

shifting the point of operation shifts the behavior of the choke depending on the linearity and other factors considered in its design and construction.

i suggest that in the absence of any detailed analysis you must go with the choke L value as suggested by the drive builder. the current specified by the drive builder must be considered as correct because the current drawn at full rated BHP of the motor, when used with a vfd, almost always exceeds the name plate current specified at full load condition.

also the higher current specified by drive builders helps the choke to run cooler by reduced current density in the conductor. the consequent improvement in L/R of the coil is an advantage in most cases.

The drive made by ABB and other things are constructed by 3rd parties..We talk to the ABB repersentatives they said it is a correct rating...But we facing the same problem above mention.

Motor Rating-3.7KW FLA-7A RPM-1440

Now give your comments

I guess you're having DTC not scalar control in action? You should be aware that even the output envelope curve looks like pretty much sinusoidal, you can't see the actual surge waves which are something else than you can quicly imagine. It loads motor and equipment after inverter heavier than sinusoidal supply. I recommend you to use these "over calculated" chokes (you didn't mention if it was du/dt or sine filter in question) rather than to order a new one in the near future by sending smoke marks :).