Best Parameter setting for VFD 1

[Phaphara]

I work at a packaging industry; we use blowers to suck the extra cuttings left at rotary die or printing. Recently we installed VFD at the blower motor.

Motor is 11KW; 3ph; the VFD is Toshiba VF-AS1 series.

I have adjusted the VFD at automatic torque boost and motor is running at 5KW at full speed i.e base frequency.

NOW the catch is that the Blower Duct Design and the motor selection is completely miscalculation. The motor is quite a lot bigger than the load. Is their any way to operate the same motor at rated frequency but less torque so the motor can be more energy efficient, or the selection i have made is the max this VFD can do.

 

[iop995]

If VFD supply 5kW to motor at rated speed it's sure an error in motor selection and for about 95% motor efficency show rated load of 4.75kW also. It's difficult to improve efficiency of such scheme and it's better to replace with a 5.5 - 6kW VFD and a 5-5.5kW motor. VFD can't change load curve

 

[Phaphara]

Thanks for the answer.
iop995

The estimated output mechanical power according to the mathematical model fed in the VFD is about 4kW.

Now this means that the system is at about 80% efficiency at the moment.SO I think it is safe to predict possible 10-15% increase in efficiency after the equipment changing.

 

[jraef]

Your basic perception that the motor is using more energy than it needs is fundamentally flawed. Unless changing the amount of flow or pressure that you want from the blower is the goal, adding a VFD will only add losses to the system.

If the flow through the system is too great, then reduce the speed via the VFD. That is what is determining the motor loading.

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[Phaphara]

English is not my first language.

So let me explain again i am talking about full load when damper is fully open. I was actually asking that is it possible to use the VFD to improve the efficiency of the same over sized motor through some parameter adjustments as motors tend to become less efficient in under load conditions.

Phaphara

 

[Dboyo]

I have a suggestion. Add more ducting... the motor can handle it and you can have one clean shop!

 

[LionelHutz]

I have seen many motors which were more efficient at 50% load than at 100% load.

Changing the motor is not an easy fix. The wrong 5kW motor will be less efficient at 100% than the 11kW motor is at 50% load.

You could try reducing the motor voltage setting in the VFD. That might save some power. However, it will likely just make up for the extra losses introduced by the VFD.

At the end of the day, a VFD is an energy waster for a motor running at 100% speed. It's not rocket science. A contactor is 99.9999% efficient and a VFD is <95% efficient.

 

[electricpete]

It sounds like there is excess torque capability with motor operating at full load, full speed, rated voltage.

In theory, a small improvement in motor efficiency can be obtained by reducing the voltage (which reduces core losses and might reduce copper losses very slightly) while keeping speed constant, similar to the NOLA. Whether the amount of motor losses saved even matches the vfd losses is still a question.


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(2B)+(2B)' ?

 

[electricpete]

Clarifcation:

It sounds like there is excess torque capability with motor operating at full load, full speed, rated voltage.

In theory, a small improvement in motor efficiency can be obtained by reducing the voltage (which reduces core losses and might reduce copper losses very slightly) while keeping speed constant, similar to the NOLA. Whether the amount of motor losses saved even matches the vfd losses is still a question.

Should have been

It sounds like there is excess torque capability with system dampers wide open , full speed, rated voltage.

In theory, a small improvement in motor efficiency can be obtained by reducing the voltage (which reduces core losses and might reduce copper losses very slightly) while keeping speed constant, similar to the NOLA. Whether the amount of motor losses saved even matches the vfd losses is still a question.

=====================================
(2B)+(2B)' ?