Earl,
I haven't worked anything as small as 5hp but most Vs drives are close. This is
by memory, but you should not see any field weakening until you hit motor base
speed. The larger drives always had a shunt on the armature leads to measure
current. The tach runs through a summing junction with reference for speed
regulation. Always remember that total field loss at speed can cause terrible
things.
Scott
On Tuesday, July 27, 2021, 3:12:51 PM CDT, Earl Weaver
<[email protected]> wrote:
On 7/27/2021 1:43 PM, Gene Heskett wrote:
> Actually, the torque goes up as the speed goes down, because they run at
> the speed determined by the counter emf generated by varying the current
> in the field winding, and the higher current actually causes it to slow
> down, but at the same time, the torque rises because the field magnets
> get stronger, generating the balancing back emf at a lower armature
> speed. Unfortunately for those motors, the non-grain oriented steel used
> in those motors is saturated magnetically, at around 1/4 of the magnetic
> field we can make with todays magnetic materiel. Not very efficient and
> it shows in the power bill to run it.
>
> My bet is that since this is a very old tech, the power supply will have
> both selenium rectifiers and wet electrolyte filter capacitors, and one,
> or the other or both have reached their retirement age, like me a long
> time back, and like me, are no longer working very well.
>
> Where are your digs located Earl? I am in north central WV.
>
>> **Earl Weaver
>> Email: [email protected] <mailto:[email protected]>
>>
>>
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>
> Cheers, Gene Heskett
Gene,
Yes, this is an approx. 1984 machine.
I suspect the drive has seen it's better days. The lathe comes out of a
tech school, hasn't been used much. Probably sat unused for "years?"
I converted it from an old Fanuc controller to LinuxCNC.
Is there a good option for replacing the DC Drive and using the existing
DC Motor, or am I better off changing to AC VFD?
I'm located up here in central Wisconsin, moved here in 2008 from
Pennsylvania.
I've been through West Virginia already. Mountainous? I still like the
mountains out east!
**Earl Weaver
Email: [email protected] <mailto:[email protected]>
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