just curious, but why single phase motor?
why not a 3 phase 600?
is the motor actually a rough service 120/240vac?

this is an interesting application.
i use variable frequency drives for hvac control applications only, not
process, but the drives that i buy and sell are made for this type of
application.

what line size do you use? to have 450 volts of line loss?

someone else on the list suggested changing to a 3 phase motor. then you
could easily run it in a number of different modes.
most of the new drives will support remote control, via wire, fibre etc.
they can be setup to be controlled manually or via a plc or other
programmable (read that PIC interface)

i have had excellent success with drives from ABB (www.abb.com)
they are not the cheapest in the small HP size motors, but i have found their
interface more intuitive, and their documentation better.

i have also used Allen Bradley. good products. the cheap ones are not very
full featured. lots of add-on pricing stuff.

i have used toshiba. although they seem like a very full featured inexpensive
drive, the documentation stinks. and the model i bought had a horrible
programming interface.

the only other thing that comes to mind with this is, normally, as soon as i
go to 600 or higher, i would never do an installation without line and load
reactors. i don't know the best practice rules for a motor that may be a long
distance away from the drive, but definately enlist the help of someone who
does or you may just find yourself buying a lot of new motors.

moose.

On March  1, 2002 07:05 am, you wrote:
> I'm fairly new to the list, and this is my 1st question, so please
> excuse me if I don't get the protocol just right, but I feel that this
> group would likely have some useful input, and I just need some help.
> I'm the 'digital' guy here, but some responsibilites overlap.
>     We need to control a capacitive run, synchronous motor. I think this
> is also called split phase. Since our industry is the oilfield, and our
> business is exploration equipment, we have some non typical
> requirements. The parameters (read:problems) are this:
> 1...This motor runs on about 600VAC, 1.25 to 2 A max.
> 2...This motor is at the end of a 25000 foot wireline. (about 5 miles)
> 3...Being split phase, there seem to be some problems using PWM control
>
>     What has been done in the past involves the 'brute force' technique.
> We connect the primaries of 2 SU-1 transformers to a variable
> transformer. While this works, we need to convert to electronic control,
> so that we can monitor the motor RPM, and adjust for optimum efficiency,
> using a MCU.
>
>     By now you have figured out that controlling 2KW of AC is not what I
> do. If I have left out some pertinent specs., please let me know.
>
>     Thanks,
>     John Marshall

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