VFD

What is your load cycle? How much is maximum and average loading on your motor? What are over load chances? What is application?

Motor is used as a mixer to mix 200 gallons of paint

Just out of curiosity, why would you think they would put a label that says "15HP" if it was not intended to be used on a 15HP motor?

Its safe but not advisable. You need to give the VSD an allowance of 15 to 25% above the rating of the drive (Motor) so that when your motor is running at FL it will not be straining( lack of a better terminology) the VSD.

But if you your load diversity, and the motor will not be running at FL all the time, you can you the same rating of VSD as that of Motor for economical reasons.

To get the best performance always refer to the manufacturer manuals.

Hope this helps.

Sometimes I am so happy that I work for a VFD manufacturer. Statements such as this mean I get to sell needlessly oversized VFds!

yup

depending on the # of starts & Stops, ventilation of the VFD [ambient temp], other than allan bradley most brands will run @ 125% of FLA [full load amps].

"safe"? "advisable"?

If it's safe, then why in the world will it not be advisable?

Thanks to all

The motor is used in driving a mixer.So how many cycles per hour.The motor will start accelerate ,run at full speed ,coast to stop.If this is correct u need the time for each portion and arrive at the rating .However a 20% margin should be safe .

YES

yes, without any hesitation.

All (North American) VFD's rated 15HP will run 15 HP motors. That is why they are name plated 15HP.

If you look at the specs you will discover there is usually a short term overload capability, that can be as high as 150% for 1 minute. Others will be 125% for 1 minute, 150% for x seconds etc. You are playing with the I^2xT thermal capacity of the devices.

The other thing to note is if the 15HP VFD is the same frame size as a higher HP unit, or is it the largest HP for that frame? Checking the spare parts list will also give an indication to what the reserve capacity of the drive is.

I agree.

I certainly will not buy any VFD without this capability.

Good thoughts, regarding VFD frame sizes. Usually the catalog numbers will indicate the frame sizes, if not, then the specification pages will tell you the physical dimensions, so you can see what ratings are in a single frame size.

One possible case where it won't drive that motor is if the motor's nameplate amps is above the VFD's nameplate amps, which can happen at times.

One caution about using the same VFD size as the motor size--if the ambient temperature is high, then the VFD's electronics will have a derated life span. Under these circumstances oversizing the VFD can avoid this shortened life span, but checking with the manufacturer's engineering people would be good.

JMM

Should be-if somebody capable designed the Inverter Circuit.

Stand near the drive.Try all speeds-while keeping Overload Trip Circuits tuned to 80%

Yes, there is no problem.

Please keep a watch on the ampere loading of the VSD and the overload withstand capability of the VSD as well.