Using a 460V VFD in a 380V environment
Using a 460V VFD in a 380V environment
(OP)
I have a 50 hp motor that is wound for 380V. I also have a 460V VFD. What kinds of issues might I face if I try to use that drive and motor in a 380V environment.
Another potentially germaine piece of info: The environment is a 50 Hz environment but I'm told that the motor will be run at 30 Hz.
I don't know the "why's" to this because the decisions were made by engineers who've left the company before I joined.
Questions:
1) What kinds of issues might I face?
2) Am I correct that for a given load, running the motor at 30 Hz will draw roughly 66% of the full-load current?
3) Can anybody point me to some good references (preferably a book I can buy but a web site would be fine) that would allow me to "get smart" on freq drives?
Another potentially germaine piece of info: The environment is a 50 Hz environment but I'm told that the motor will be run at 30 Hz.
I don't know the "why's" to this because the decisions were made by engineers who've left the company before I joined.
Questions:
1) What kinds of issues might I face?
2) Am I correct that for a given load, running the motor at 30 Hz will draw roughly 66% of the full-load current?
3) Can anybody point me to some good references (preferably a book I can buy but a web site would be fine) that would allow me to "get smart" on freq drives?
--------------------
Bring back the HP-15
www.hp15c.org
--------------------





RE: Using a 460V VFD in a 380V environment
The output AC voltage will always be lower thean the input voltage. If you run the motor on 30 Hertz output the drive will put out 60% output voltage but your torque should be about the same. If a motor is running too slowly either the cooling fan will not blow enough air or the induced voltage in the rotor will drop to zero. Most motors will withstand 15 Hertz operation with factory cooling fan and 6 or 10 Hertz with a sperately powered fan.
Mike Cole, mc5w@earthlink.net
RE: Using a 460V VFD in a 380V environment
Be sure to put the correct motor nameplate data into the drive software. That way, the output will be limited to 380V/50hz and the motor doesn't know the difference. The drive will behave properly too. Be sure to check that the drive has the ampacity to fully power the motor.
As for motor current, that depends entirely on how heavily the motor is loaded. That statement is true at 30hz as well as at 50hz. Pretty much any 50hp motor should be able to tolerate a 2/1 speed turndown. More often 3/1 is ok in this hp range.
RE: Using a 460V VFD in a 380V environment
DickDV brings up a good point, mainly that all things are not equal among VFD manufacturers, so there is no generality that can apply. What VFD do you have? Many people who participate in this forum have a world of experience with VFDs and most likely several of us have (or can get) enough information on your to be able to give a better answer.
"Venditori de oleum-vipera non vigere excordis populi"
RE: Using a 460V VFD in a 380V environment
--------------------
Bring back the HP-15
www.hp15c.org
--------------------
RE: Using a 460V VFD in a 380V environment
http://www.baldor.com/pdf/manuals/722-803.pdf
"Venditori de oleum-vipera non vigere excordis populi"
RE: Using a 460V VFD in a 380V environment
Most drives today are built for only 2 voltage ranges. One range is 200 to 240 volts input and the other is 380 to 480 volts input. This keeps things simple from a manufacturing and stocking standpoint.
If you are in doubt, call the manufacturer to find out what the drive can do.
A possible alternative is to use buck boost tranformers to create a wye primary wye secondary autotransformer that steps up to 440 to 480 volts so that the logic and analog buses will have enough voltage. Three 220 volt 44 volt tranformers would give you about 264Y459 volts at no load. That should be good enough to run the drive.
Mike Cole, mc5w@earthlink.net
RE: Using a 460V VFD in a 380V environment
These are on page 21 of their catalog.
Mike Cole, mc5w@earthlink.net