TO ALL GENIUS OUT THERE, PLS HELP: anybody cares :^_^

sheryl86_ann · Oct 29, 2008

Pardon me but this is not totally related to plc.
I encountered problem regarding with frequency inverter. This is our site set-up:

We are going to install 11KW FR-F740 11K Frequency Inverter which will control two (2) 5.5 KW motor loads with different rotation : say one is in clockwise rotation while the other one is counterclockwise rotation.

Our plan is to connect each at inverter terminal one at FORWARD START (STF)and COMMON (SD) while the other at REVERSE START (STR) and COMMNON. Please note that it is using only one inverter. Is it possible.

Do we still need to inter-change the line connection for the other motor and connect it this way?

Blessing,

sheryl caño- phil.

JesperMP · Oct 29, 2008

After reading this post 3 times, I have come to the conclusion that you must be confusing the command terminals for start/stop/forward/reverse with the output terminals for the motor(s).

You can connect several motors in parallel with one VFD.
I am assuming that they must run simultanously (why else would you use an 11kW VFD for 5.5 kW motors).
Normally you add an output choke when one VFD has to control several motors or the motor leads are very long.

That one motor runs CW and the other runs CCW is irrelevant for the VFD. You just connect to motor cables in the motor terminal box so that they run opposite of each other.

You must protect each motor individually. Best is with Winding Thermistors because of the VFD operation.

sheryl86_ann · Oct 29, 2008

JesperMP said:
After reading this post 3 times, I have come to the conclusion that you must be confusing the command terminals for start/stop/forward/reverse with the output terminals for the motor(s).

You can connect several motors in parallel with one VFD.
I am assuming that they must run simultanously (why else would you use an 11kW VFD for 5.5 kW motors).
Normally you add an output choke when one VFD has to control several motors or the motor leads are very long.

That one motor runs CW and the other runs CCW is irrelevant for the VFD. You just connect to motor cables in the motor terminal box so that they run opposite of each other.

You must protect each motor individually. Best is with Winding Thermistors because of the VFD operation.

do we still need to alter the 2nd motor connection considering we will use the FORWARD and REVERSE VFD terminals? (attached file)

JesperMP · Oct 29, 2008

The image is very poor so it is near impossible to figure out what the control circuit does.
Also, it is not clear to me what you want to achive.
Are the two motors for example coupled to the same mechanical system, or are they running completely independent of each other ?
Are the motors supposed to be reversible ?
Shall they always run simultanously, or always alternatingly, or can it be both ?
What is the purpose of the contactors that bypass the VFD ?

Goody · Oct 29, 2008

Whatever way he means to control those motors - that drawing shows that one day there will be a big boom.

If C4 or C5 ever stick in - on the next run the 3 phase will get to the output terminals of the VFD. I have seen this happen, there is not a lot left of the drive

TO ALL GENIUS OUT THERE, PLS HELP: anybody cares :^_^

sheryl86_ann

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JesperMP

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sheryl86_ann

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JesperMP

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Goody

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