JLAB-TN-08-056
C50 Cryomodule Cavity Tuner Study – Evaluation of Planetary Gear Box
Installed on Tuner Mechanism
Hrishikesh Phadke, Ed Daly
1. INTRODUCTION
As part of NL-12 decommissioning, tuner testing was conducted on cavities 1 and 2 to
determine the tuning sensitivity and backlash with planetary gear box added to the original
CEBAF tuner system. The necessity of high torque output made the installation of the gear box
necessary into the system. With 3:1 gear ratio the gear box facilitated three times higher torque
output. The disadvantage of using the gear box is the increased number of rotations to achieve
the same frequency change. An alternative solution to increasing torque would be installation of
higher torque motor. A higher torque motor would require changing the input connections to the
motor and thus would be a costly alternative. Hence it was decided to use a gear box with higher
torque output.
Figure 1: Lab view GUI showing Frequency Settings and Sensitivity Curve
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2. INITIAL DATA FOR THE TESTS
Number of steps of motor= 6000
Full Range Span on Network Analyzer= 4 KHz
Velocity = 25 rpm
Acceleration = 10 rps/s
High Frequency Limit= 1497.002 MHz
Low Frequency Limit= 1496.998 MHz
3. TEST SETUP
Description of Gear Box
Company:
Neugart USA, LP
3047 Industrial Blvd.
Bethel Park, PA15102-2537
Specifications of Motor:
PLE60 i=3/OPX/NEMA 23 Stepper
Ratio: 3 (1 Stage)
OPX= NEMA 23 Output Flange
270-526- Adapter Flange 60X60- PLE60 –NEMA23
23/38.1/66.7/B5/M4
210-140- Bushing /Sleeve-d= 14/6.35
210-445- Output Adapter Flange 60X60- PLE60-NEMA 23
With motor mounting screws (M4X12)
S/N: 501845-010-001
Figure 2: Gear Box Installed on Cavity
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4. TEST RESULTS AND DISCUSSION
The difference between the frequency values from the experiment and the pressure
compensated frequency is negligible. Hence the frequency values from the experiment have been
taken to plot the graphs.
a. First Test on Cavity 1
With Gear Box
1497.0021
1496.9979
Initial Frequency f0 (MHz)
Final Frequency ff (MHz)
Table 1: First Set of Frequency Readings for Experiment on Cavity 1 with Gear Box
Frequency (MHz) Vs Microsteps
With Gear Box
1497.002
1497.0015
Frequency(MHz)
1497.001
1497.0005
1497
1496.9995
Slipping
1496.999
1496.9985
1496.998
-150
-100
-50
0
50
100
3
Microsteps * 10
Figure 3: Frequency Sensitivity for Test 1 on Cavity 1
The backlash at the beginning of the experiment is approximately 25000 steps. The
frequency decreases until 1496.997 MHz, then the direction is reversed and again a backlash of
37000 steps is observed. This is a very high backlash for 3:1 ratio stepper motor. The coupling
between the motor and gear box was suspected to be loose, causing slippage. The coupling was
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tightened and the test was conducted again. To avoid this problem in production, a keyed
coupling or stepper motor with a flat on the shaft is recommended.
b. Second Test on Cavity 1
With Gear Box
1496.998
1497.00009
Initial Frequency f0 (MHz)
Final Frequency ff (MHz)
Table 2: Second Set of Frequency Readings for Experiment on Cavity 1 with Gear Box
Frequency (MHz) Vs Microsteps
1497.002
With Gear Box
1497.0015
Frequency(MHz)
1497.001
1497.0005
1497
1496.9995
1496.999
1496.9985
1496.998
-50
0
50
100
150
3
Microsteps * 10
Figure 4: Frequency Sensitivity for Test 2 on Cavity 1
The backlash at the beginning of the experiment is 38000 steps. The frequency decreases
until 1496.997 MHz. After the direction is reversed, a backlash of 37000 steps is observed.
Tightening the coupling eliminated the slippage. The backlash did not change, remaining 37000
steps. Tuner hysteresis data for cavity 1 without the gear box is unavailable because testing was
not conducted on this production cavity. Data for all other cavities is available.
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c. First Test on Cavity 2
With Gear Box
Without Gear Box
1497.002918
1497.0021
1496.9981
1496.9989
Initial Frequency f0 (MHz)
Final Frequency ff (MHz)
Table 3: First Set of Frequency Readings for Experiment on Cavity 2 with Gear Box and
Without Gear Box
Frequency (MHz) Vs Microsteps
1497.003
1497.0025
With Gear Box
Without GearBox
1497.002
Frequency(MHz)
1497.0015
1497.001
1497.0005
1497
1496.9995
1496.999
1496.9985
1496.998
-200
-150
-100
-50
0
50
3
Microsteps * 10
Figure 5: Frequency Sensitivity for Test1 on Cavity 2
Backlash at the beginning of the experiment is 38000 steps. Backlash at direction reversal
is 32000 steps. The cavity frequency sensitivity with the gear box is 0.025 Hz/µstep, while the
cavity frequency without the gear box is 0.075 Hz/µstep. The gear box reduction (3:1) changes
the cavity frequency as expected.
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d. Second Test on Cavity 2
Initial Frequency f0 (MHz)
Final Frequency ff (MHz)
With Gear Box
Without Gear Box
1497.0021
1497.0031
1496.9981
1496.9989
Table 4: Second Set of Frequency Readings for Experiment on Cavity 2 with Gear Box
and Without Gear Box
At the start and at direction reversal, an equal backlash of 38000 steps is observed. The
program is again terminated as the frequency reaches upper limiting frequency of 1497.003
MHz. The cavity frequency sensitivity with the gear box is 0.025 Hz/µstep, while the cavity
frequency without the gear box is 0.075 Hz/µstep. The gear box reduction (3:1) changes the
cavity frequency as expected.
Frequency (MHz) Vs Microsteps
1497.003
With Gear Box
Without GearBox
1497.0025
1497.002
Frequency(MHz)
1497.0015
1497.001
1497.0005
1497
1496.9995
1496.999
1496.9985
1496.998
-200
-150
-100
-50
0
3
Microsteps * 10
Figure 6: Frequency Sensitivity for Test 2 on Cavity 2
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5. CONCLUSION
The 3:1 ratio stepper motor reduces the cavity frequency sensitivity by a factor of three.
Throughout the experiments a consistent backlash of approximately 37000 steps has been
observed and is consistent with CEBAF tuner performance. Slippage between couplings can be
reduced by adding keys or flats on motor shaft. The controls and data acquisition program should
be improved to run more stably.
6. FURTHER WORK
This test was conducted on a cryomodule that is scheduled for disassembly. The tuner
mechanisms possesses large backlash because of original hardware limitations. The
refurbishment effort includes adding an improved tuner transmission which reduces the backlash.
More tests should be done on refurbished cryomodule, such as C50-CM7, to evaluate the
gearbox performance on an improved tuner mechanism.
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