I do like the Half Farmer bit
Anixter Edmonton
Thanks!!!
....
It looks like it was crap from the day it was born. UNLESS....it likes to smoke after sex.
IIRC, there is a setting up in the P108 or somewhere that has to be changed also. That locks the startup freq to 60 or whatever you set.
04/25/2019 12:08 PM
|
| There are several issues with this. First off is the winding insulation. VFDs work by “tricking” a motor into reacting to a string of DC pulses as if it is AC power. In creating those DC pulses, the wiring between the drive and motor can act like capacitors and great higher voltage pulses that are superimposed on the circuits, then those bounce back and forth between the drive and motor in waves (called “reflected waves”) that build up to being spikes that are as much as 2.5 - 4x the normal voltage. In 480V drives then, it’s not uncommon to see these spikes reach over 1400V, sometimes as much as 2000V. Older motors used magnet wire in the windings that had 1000V insulation, later 1200V, both of which are inadequate when subjected to these stresses. The thing is that on older motors, you have no way of knowing what was used unless the mfr is still available to ask, and good luck with that even if. But on 230V motors, that 1200V insulation is fine and if the distance from drive to motor is short, even 1000V is OK. The other aspect is with the bearings. The same effects that cause the reflected waves also cause a static voltage to build up between the stator and rotor and once that builds up to being higher than the dielectric resistance of the grease, it will jump across the bearings and races. In doing so, it causes little microscopic pits, called EDM (Electric Discharge Machining; like welders and plasma cutters) and over time these pits become frost-like and then eventually grooved flutes that destroy the bearings and races. Inverter duty motors take measures to prevent this, older motors didn’t because that issue didn’t exist on a widespread basis. There are retrofit “shaft grounding rings” that you can add to existing motors to deal with this risk If you can keep the VFD within 25ft (linear) of the motor, the voltage and bearing issues are unlikely to affect you, so long as you resist the temptation to get rid of the “whine” that the motors make on a VFD by increasing what’s called the “carrier frequency”, which is the rate at which the DC pulses are fired. Increasing the CF will move the sound out of the range of human ears, but makes the motor problems worse, especially on older motors. A third aspect is cooling of the motor. ODP and TEFC motors rely on shaft mounted fans to move air across them to keep them cool. The fans then are slowed down with the motor speed and the way these fans work means that the air flow drops faster than the speed change. So at slow speeds, the motor receives less cooling effect and can burn up without being overloaded. If you add a separately powered blower to move air across the motor when operating slower, you can solve the heating issue too. Or, as many people do, you use your older motor until it dies, then replace it with a newer inverter duty motor. It depends on what the down-time will cost you. |
It looks like it was crap from the day it was born. UNLESS....it likes to smoke after sex.
I don't think you did any thing wrong. The transformer I was talking about is a small one that powers the mag switches and is on board the 3 phase mill. But you are using a shaper so that is not applicable, unless you have mag switches on it.
I do recall a variable dc power supply I bought, now that you mention it. Vevor wanted a home movie and lots of cleavage, so I showed them a plumbers crack.
But meantime I figured out I had hooked it up backwards, and popped a large diode on the board. We did the do-see-do for a while and then Vevor sent me my money back. I turned around and bought a bigger power supply from them with it, and got a diode from mouser and soldered it in, so now I have two power supplies.
