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Coles County, Illinois | Some good points posted above about VFD's. It's hard to generalize about VFD's as the technology is changing at such a rapid rate. I first worked with/on VFD's in 1985. They were Parajust brand. A 2 hp model was around 2'X2'X 8" deep and weighed around 30 pounds about $4000.Adjusting them took extensive knowlege Quick overload conditions would blow a diode in a chopper board. This occured often. In 1990 we switched to Allen Bradley 1336 cost was 1/2 as much and reliability much better they were 12"X 10"X 6" for a 2 hp and could accept 4-20ma signals. The only real problem with them was low torque at slow speeds and if you tried to start them against a dead short they would literally pop. Time to replace whole unit.With these units we began to notice that standard motors would get weak if we had long runs between the drive and the motor.We found out that solid state inverters have high voltage ringing in the motor leads. This 1700V signal would slowly degrade the 1200V insulation of the motor coils.Where we could we moved the drives closer to the motor as the wavelenght needed 33' to get above 1200V. In other places we bought inverter rated motors with higher rated coil insulation.
This is getting long. If anyone wants me to continue, just post so. | |
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VFD torque
