About Frequency Drive

If the drive has been correctly programmed, then it is preventing the motor from burning out by tripping the motor off. Phew!

First impressions suggest that either:

• the motor needs to be larger and the drive and possibly the wiring may need replacing to accomodate a larger motor, or
• a reduction in the load would enable the same motor/drive/wiring combination to be used.

Current is proportional to torque, very nearly. Motor power is proportional to both torque and speed.

What are the characteristics of the load, though?

Greetings,

All variable frequency drives pretty much are programmable with most drives capable of providing up to 160% of the design rated motor torque during starting periods for a short time interval.

I believe that your drive is not programmed correctly for the starting load-demand and most likely is not programmed for correct running peformance either.

There should be a set of programable parameters associated with your particular drive and software (if required) available from the original equipment manufacturer.

If you do not have the required information or cannot understand the configuration instructions, my advice would be to contact the O.E.M. for support as most manufacturers are very willing to support their products.

First, check if the parameters on the frequency drive have been entered correctly.

If the parameters are correct, check your phases to make sure they're all there (assuming you're using three phase).

If the phases are there, check to see if they're balanced. If they're not balanced, check the motor winding resistances.

Check the motor insulation.

If everything checks out as okay, your load is probably too big for your motor and drive. Either reduce the load or change to a bigger motor and drive.

Hope I didn't forget anything.

Dear Singh, There are many VFD drives available in India such as Siemens,Telemechanique, Allen Bradley. You can select one of them and use them.Also there are mechanical PIV drives which provide you variable speed.

sir,we are allready using invertek vfd drive variable speed,but my question is that same rating drive on same rating motor is sufficient or drive rating should more.

hello,

your question is not quite as simple as you think, if the drive type is matched for the load type then you should be OK. For example, there are what are called fan or pump drives (variable torque) and (constant torque) drives. if your trying to use the drive on a crane ( constant torque) and the drive is for fan or pumps (variable torque) then you will have to increase the drive size by at least the next larger. if the drive is rated (constant torque) then an equal match motor to drive size is going to be ok.

I hope this helps

Dave

If your drive and motor are rated for the application, then they should be fine. As suggested above, be sure to ck your parameters to see that everything is set properly. You should keep in mind that you have a lose of about 1 amp per 100 ft on shielded cable and .75 per 100 ft on a regular type cable. Especially on smaller motor and drive apps, you'll find it neccessary to install a larger drive than the motor. Also, manufs, such as Allen Bradley, offer drives that have an HD (heavy duty) rating to compensate for apps where increased loads could come into play.

Dear Mr.Singh, If motor is tripping then either it is overloaded or the Overload relay is not set properly or starting torque required is more such as in Cranes.First check suitablity of motor, if it is o.k for 20 Hp then you can use same VFD.

sharma ji i think you all ready work on same drive i want to ask a question motor frequency in india 50 hz and on frequency drive there is also setting for frequency its also must be same or depend on motor frequency,i am little confused there is no auto tuning like eurotherm drive please suggest me we are using gear box with motor rated 1/3 there speed is constant and one thing they all ready mention connection delta,or star both side current is different because in star underroot 3 voltage and delta line voltage,please suggest me sir i am confused before we always using dc drive after getting some information from people we are now want to use frequency drive please suggest me. thanks joginder pal singh

Dear Mr. Joginder,

Frequency of motor is no matter with variable frequency drive, example, if your system is 50Hz and you have space problem or limited space for installation of of motor then you can go for 60Hz motor.

Motor is always connected in Delta( as far as my experience is concerned on Siemens- simovert master-drives, Fuji Frenic Drives, danfoss drives, lenz drives Etc..)

Regarding your very first question , I just say in some applications you can use same rating of drives. You can keep starting current limited by adjusting acceleration/ramp up time through your parameter settings.