How to size a VFD 

An oversized VFD is fine, the same way it's fine to plug a 10A load into a 20A circuit (the AC power feed from the wall to the VFD will need to be rated high enough for the load applied, 2X the 3-phase current). Other way around (20A load on a 10A circuit) won't work.

Ryan, I am not sure what you are asking. The overload rating is not a setting, it is a specification of the VFD. Can you elaborate your question? If you have questions about programming, we have a few other videos showing how to program a VFD. In those videos, we used all Mitsubishi VFDs, but the parameters you need to set are the same.

No

Run, no. Probably destroy, yes.

+ian jemar Yu Hello Ian, what is your application and is the circuit breaker sized properly?

its application is in Food Manufacturing. SILO process sir. the set of it is one vfd driving a two rotary valve motor and it is design by Guerin. The circuit breaker is in standard size, phase current is normal if we check. we always change circuit breaker according to designer advice but still re-occurrence of happen. i am wondering why, the circuit breaker is new, new motor, normal phase current but circuit breaker always becoming hot. VFD with two circuit breaker which command two motor for transferring of product in a chute or pipe.

+ian jemar Yu We would recommend having a certified electrician to install this for you. It is very likely that the circuit breaker is not the right amperage rating (what I was referring to earlier about size. It is likely too low). The amperage rating of the breaker needs to meet your national electric code.

Just looking at the amperage, yes, you can use a 8.2A drive on a 7.5A motor. But other factors such as attitude, ambient temperature, and the type of application will make a difference also.

Hi Sir, Attitude - Unknown ambient - Max 40 deg C Application - Booster Pump Is it ok ? Does it help if I prolong the time (20-30seconds) to full speed. If the VFD is undersize, will it damage to my VFD or only tripping ? Kind regards Ray

Ray, you can set the acceleration time to 20-30 seconds, but we do not recommend using an undersized VFD. The diodes in your VFD may be permanently damaged when operating a larger motor.

OK, noted.... Thanks a lot...

Ray, I am not understanding your question. What is your input power, motor, and VFD spec?

Our electrical characteristic is 415V 3Ph 50Hz. Can I run a 60Hz 440-460V motor with VFD (input power 415V 3Ph 50Hz). or I need to add transformer to convert the electrical characteristic to 460V 3Ph 60Hz before VFD Input. Kind regards Ray

Ray, You can get a 460V, 3Ph VFD for your setup. You don't need the transformer. The VFD will run at 60Hz at 440-460V.

Hey Matt, you will have to derate the drive to make it work. If your motor is rated for 5 amps, you need a drive with 10 amps or more. Make sure there are nothing (switches, lights, etc.) between the drive and the motor. Put them after the motor or on a different circuit if you can. Hope that helps!

+VFDs.com Ok, so here's the thing, I have some shop equipment that I bought that is 480v 3 phase, all I have is 220v. So if I add a transformer to bump it up to 480 and then add a a vfd that is rated at twice the amps to that my motor needs I should be good? The vfds I see all say 480v 3phase input. Thanks for the reply!

Matt, If you have 1 phase 230V power and 3 phase 460V machines; yes, that will work. The transformer will convert 1 phase 230V to 1 phase 460V. Then you can use the VFD to convert 1 phase 460V to 3 phase 460V. Here are a few things you should beware of: (1) this is the arrangement you should have: Power from the wall > transformer > VFD > motor (2) if your transformer is big enough, you can use it with multiple VFD & motor setups (3) again, nothing in between the VFD and motor Let me know if you have other questions!

You should also look at the overall cost, to see if it is worth getting new machines that are 230V instead of the transformer.

Well, got a good deal.. You know how that goes.. I paid one price for everything in the garage. Only the Cincinnati buffer is 480v I don't have to have it working, but it would be nice.

Ehsan, what is the amps on the motor? What is the "i" that you are referring to?

VFDs.com hi amps of the motor is 11.4 .I read it from name plate. thank you

Ehsan, you will need a VFD with 11.4 or higher amps.

VFDs.com Thank yo so much for support

You are welcome!