DRO or VCD?

Turbo can correct me if this is wrong, but everything I have ever read states that there should be nothing between a VFD and the motor? Or does that only apply to disconnects?

BTW.... what is a reactor? :-[
 
Highpower link=topic=1532.msg9587#msg9587 date=1302446350 said:
BTW.... what is a reactor? :-[
Click to expand...

It's a great big building, with atomic energy inside. But that's not important, now... :D
 
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Another VFD question: Do you buy the VFD for the rated HP of the motor, or is it necessary to upsize, to account for any kind of loss in the transition?

My mill is 1/2HP, 3ø. This looks like the VFD that I should have: http://www.driveswarehouse.com/Drives/AC+Drives/Micro+VFD/L100-004MFU.html.
(...aside from the sheer magic of inputting 110v, single phase, and getting 220v 3 phase out of it.) Can I just put a HD cord onto it, and plug it into a 15 amp line?
 
Another VFD question: Do you buy the VFD for the rated HP of the motor, or is it necessary to upsize, to account for any kind of loss in the transition?

I learned that the mill is only 1/2HP, 3ø. So this looks like the VFD that I should have: http://www.driveswarehouse.com/Drives/AC+Drives/Micro+VFD/L100-004MFU.html.
(...aside from the sheer magic of inputting 110v, single phase, and getting 220v 3 phase out of it.) Can I just put a HD cord onto it, and plug it into a 15 amp line?
 
wawoodman link=topic=1532.msg9588#msg9588 date=1302446551 said:
Highpower link=topic=1532.msg9587#msg9587 date=1302446350 said:
BTW.... what is a reactor? :-[
Click to expand...

It's a great big building, with atomic energy inside. But that's not important, now... :D
Click to expand...
OK, thanks! And don't call me Shirley... ;)
 
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turbinedoctor link=topic=1532.msg9203#msg9203 date=1302133560 said:
Paul in a case like yours with such a small second motor and load, if it were mine I would try starting the coolant pump with the main motor running if it were needed. Chances are it wont see much difference. If it does then start them both together.

The three motors I wired one one VFD was the old way with no reactor between the VFD and motor. Now days I think they like reactors after the VFD and maybe before it.


Turbo
Click to expand...
Tubro
Yes, I do start the two at the same time. I dont know if the VFD would trip out starting it separate, not somthing I would try. To the other poster, yes you are correct, there should be no switches, relays, and the like between VFD and the motor. Mine is set up with a disconnect , so I have the choice, either Im starting the two together, or just the main motor.

Just to make it clear, on my set up, It is only a way to run two motors on one VFD. The disconnect allows me to chose one, or both. The second motor, the coolant pump in my case is never switched on or off while the VFD is powered up.

This is not the standard thing to do, with a VFD, but my VFD doesnt even notice the extra load the coolant pump draws. Keep in mind the load is low, its only moving coolant. My machine is of 575 volt variety, and both motors run fine on a single VFD. I dont see it worth buying a separate VFD just for a coolant pump. If it come down to the wire, I would just swap out the coolant pump motor for a 120 volt single volt motor.

Paul
 
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wawoodman link=topic=1532.msg9590#msg9590 date=1302447153 said:
Another VFD question: Do you buy the VFD for the rated HP of the motor, or is it necessary to upsize, to account for any kind of loss in the transition?
Click to expand...
From what I can tell, only if you are operating in an ambient temp over 40 deg C, or at an altitude over 1000 feet.
See: http://www.hitachi-america.us/supportingdocs/forbus/inverters/UserManuals/L100_NBS541X_3.pdf

It looks like the rated input (single phase) is 5.8 amps on that unit, so I think you will be fine on a 15 amp circuit.
If you get into the higher carrier frequencies on the VFD, you may have to do some de-rating though.

Take all of this with a large dose of salt mind you.... ???
 
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Joe

Chokes also called reactors are inductive coils that smooth out the wave form from the VFD. They are usually only required if there are more than one VFD operating on a single piece of equipment. IE if the lathe motor and coolant pump are being seperated connected to VFDs. This would be done so that the coolant pump is not being slowed down and have low coolant flow even though the main spindle motor is reduced to a crawl.

Mike

Old VFD's had to be derated by 0.73 as they were speced for 3 ph in and 3 ph out. Most manufacturers that supply these devices have built that into the specs. If it is rated as 1/2 HP 220 V 1 PHase in to 3 Phase out, it has already been derated. If not then yes you need to pick a VFD that is the next larger in size

Walter
 
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