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jet 1442
- Thread starter tmmk
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If you are patient and peruse the eBay listings for 3-phase motors and VFD's you can come up with some good deals. You might want to consider mounting the motor so that it faces the other direction. I would get rid of the variable pulleys and replace then with fixed step pulleys.
There is a dark side to using electronic variable speed control when compared to mechanical variable speed control that most people are not aware of: with mechanical variable speed control, the full rated horsepower (less power lost in the drive train) is always available at the load. This means that at low spindle speeds in a mechanical drive, tremendous torque is available at the load. Electronic drives, on the other hand, cannot produce any more torque at low speed than they can at base speed (meaning when the drive frequency is 60 Hz). So below base speed, the available torque is constant while horsepower decreases linearly with speed. Above base speed, horsepower remains constant and torque decreases. The bottom line is that you will either have to use multi-step sheaves to optimize torque at different speed ranges or get a much larger motor to make up for the lost torque at low speeds if using electronic speed control and a single drive ratio.
When you get a 3-phase motor, not just any old motor will do -- it needs to meet several criteria:
There is a dark side to using electronic variable speed control when compared to mechanical variable speed control that most people are not aware of: with mechanical variable speed control, the full rated horsepower (less power lost in the drive train) is always available at the load. This means that at low spindle speeds in a mechanical drive, tremendous torque is available at the load. Electronic drives, on the other hand, cannot produce any more torque at low speed than they can at base speed (meaning when the drive frequency is 60 Hz). So below base speed, the available torque is constant while horsepower decreases linearly with speed. Above base speed, horsepower remains constant and torque decreases. The bottom line is that you will either have to use multi-step sheaves to optimize torque at different speed ranges or get a much larger motor to make up for the lost torque at low speeds if using electronic speed control and a single drive ratio.
When you get a 3-phase motor, not just any old motor will do -- it needs to meet several criteria:
- the winding insulation must be rated for inverter duty -- class H
- look at the minimum and maximum speed of the motor -- a TEFC motor gets less cooling at low speed and will run hot and is less efficient at high speed and will run hot there too. Some inverter rated motors only have an allowable 4:1 speed range.
- TEBC motors are more suitable since the fan runs at constant speed.
- The best TEBC motors (and most expensive) will have a 1000:1 speed range with a maximum speed around 4X base speed.
- There is no question that you will want to get at least as much low speed torque as you currently get so the motor size and drive ratio will need to be carefully designed to ensure that condition is met.
Thanks for the info Bill. That pretty much explains the difference in price for the 1642 and makes it sound like a bargin all at the same time! 😱