Problem-Solver, Series 16
A major manufacturer of quality, high tech ceramic powders was experiencing problems on their 75 hp, 1750 rpm AC brake motor.
The first problem encountered was frequent motor burnout due to the high starting torque requirements.
This continued even after changing from NEMA B to NEMA C motors.
Secondly, the brake could not accurately stop the mill fast enough to position the mill for loading raw product or unloading the finished material.
These problems were expensive to the customer in both maintenance costs and lost production. More importantly, they posed a potential safety problem.
If the mill was not positioned properly by the operation of the brake, maintenance personnel were responsible to accomplish this manually, using chain falls and large pry bars. This could be a dangerous situation due to the location of the mill.
Our local Rexnord distributor was called after a motor burnout and asked to quote a 100 hp NEMA C brake motor. Our distributor told them that he had a better solution to the problem.
Current Problems
Frequent burnout of the main ball mill drive motor. This was caused by the high starting torque requirements.
The AC motor brake was not large enough to accurately stop the mill in the load and unload positions.
Mill overload conditions can occur causing high overload condition on the AC motor, drive and mill gears.
The True Torque Solution
The True Torque fluid coupling allows full use of the motor breakdown
torque. The fluid coupling allows the motor to achieve normal operating
speed before the high torque is transmitted to the load.
The brake was moved to the drive high speed shaft eliminating the need for the special AC brake motor. Since it was now on the output side of the AC motor its overrunning inertial effects were eliminated.
The stopping accuracy problem was solved.
The True Torque fluid coupling limits the maximum transmitted torque protecting the driven equipment and increasing machinery life.
Implementation
The Rexnord representative suggested a 420HFD fluid coupling be installed between a standard 75 hp, NEMA B, AC motor and the
Falk 8C2 drive. The customer was assured the coupling would allow full use of the AC motor torque for starting without motor burnout due to overheating. A
True Torque G66 brakewheel was supplied for mounting on the drive high speed shaft taking advantage of the customer's standard brakes.
Since the installation of the True Torque fluid coupling and the new brake arrangement, starting and motor burnout problems have been eliminated and the mill can be stopped in the proper position.
The Rexnord solution was 3 times less expensive than going to a 100 hp brake motor, fits into the same space as the original equipment and provided the needed solution to a very real safety problem.
Production is up and maintenance costs are minimum.
To say the least, the customer is satisfied with the solution and stated that
True Torque fluid couplings will be purchased to replace competitive units on 12 other applications in his plant.
CONTACT YOUR REXNORD FLUID COUPLING DISTRIBUTOR FOR THE SOLUTIONS TO YOUR POWER TRANSMISSION PROBLEMS.
Form 891201
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