During full power/torque operation of the ASD and Coupling, they are designed to operate with only 1.5% slip (at 98.5% efficiency) and will produce no noticeable heat on the Induction Rotor. This highly efficient power transfer is inverse to electronic VFDs, where their losses and heat generation are a maximum at full power operations. This condition requires the VFD to provide maximum cooling at the highest power levels and results in substantial energy losses that are documented to be between 5 – 7%. In many VFD installations, climate controlled rooms are required at a cost of additional space and power.
During variable (reduced) speed and power operations for centrifugal systems (i.e., pumps, blowers, and fans) the Flux Drive ASD is slipping to adjust the output shafting to meet the required system flow rates. During this condition, heat will be generated on the induction rotor and dissipated in the cooling fin design. A maximum fin temperature of 350 degrees F can be normal for steady state conditions at reduced RPMs and be well within design specifications. Exhaust air from the cooling fin is typically about 150 degrees F. The point in the speed range of maximum heat generation will be at 33% slip (note that the power is reduced to only 35% based on Affinity power curve), but is generated at a point in the cubic power curve that has much less power losses when compared to maximum VFD losses (4 - 6%) at 100% power.
In constant torque applications, speed reduction is limited with all mechanical adjustable speed drives including the Flux Drive ASD. Since the power required is not actually reduced during the speed reduction to the driven load (the torque is constant), the Flux Drive ASD is limited to a ten (10) percent reduction in speed (turn down) unless the ASD is oversized for the specific application with Flux Drive pre-approval. This is due to direct heating issues that occur since the load torque (and corresponding power consumed) is constant throughout the entire speed / operating range.
It should also be noted that constant torque applications provide limited energy savings during any reduction in speed of the load shaft. There are no restrictions in operation for constant torque loads with the Flux Drive Coupling. The coupling’s ‘soft-start’ capability is not limited and the performance is excellent with full torque / power performance at 98.5% efficient. Examples of constant torque loads are conveyor systems, feeders, winders, mixers and positive displacement pumps and compressors.
The ‘soft-start’ capability is inherent in the Coupling and ASD designs and ultimately limits the full torque / power at start-up (and all operating conditions) to 140 percent of the couplings full rated power. No longer is a motor subject to high locked-rotor currents nor does the electrical system have to provide high peak power during a motor starting event. In addition, the coupling provides over torque protection during a load shaft seizure by also limiting the torque and power to a maximum of 140 percent of full rated power / torque.
Both the ASD and Coupling will limit the maximum torque/power delivered during the seizure event to 140% – 150% of the rating of the Motor and Flux Drive (if sized based on motor nameplate data). During this event, the Class 10 motor trip will trip the motor after the predetermined time (typical 30 – 40 sec) and save the system from catastrophic damage.
The Flux Drive ASD uses a Rotork® electronic digital electric actuator to automatically adjust the speed of the ASD output shaft based on an analog control signal (4-20 mA or 0-10 volts). The actuator provides smooth, highly accurate positioning (speed control) with positive position-lock when not in motion. These rugged actuators may be mounted in any position and will withstand the most adverse environmental conditions.
We recommend installing the Magnet can on the Motor shaft to make it easier to perform maintenance on the NDE (non-drive-end) pump, blower or fan. By leaving the entire Magnet Can and Rotor assemblies installed on the motor, the flexible disk pack can be dis-assembled (by removing only 3 fitted bolts) and then the complete Motor and Flux Drive assembly can now be moved to the side allowing access to the NDE machine. Note: during this process, the Induction Rotor assembly should be centered in the Magnet Can using the plastic shim spacers and the four (4) jacking bolts provided.
In the case of a gearbox, the Magnet Can should be mounted on the gearbox to allow the induction rotor fan to run at maximum speed all the time. This provides maximum cooling, which may be required for constant, high torque devices.