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 necessaryinto 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

  1. 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

  1. 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 BoxInstalled on Cavity

  1. 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.

  1. First Test on Cavity 1

With Gear Box
Initial Frequency f0 (MHz) / 1497.0021
Final Frequency ff (MHz) / 1496.9979

Table 1: First Set of Frequency Readings for Experiment on Cavity 1 with Gear Box

Figure 3: Frequency Sensitivity for Test 1 on Cavity 1

The backlash at the beginning of the experiment is approximately 25000 steps. The frequency decreasesuntil 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 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.

  1. Second Test on Cavity 1

With Gear Box
Initial Frequency f0 (MHz) / 1496.998
Final Frequency ff (MHz) / 1497.00009

Table 2: Second Set of Frequency Readings for Experiment on Cavity 1 with Gear Box

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.

  1. First Test on Cavity 2

With Gear Box / Without Gear Box
Initial Frequency f0 (MHz) / 1497.002918 / 1496.9981
Final Frequency ff (MHz) / 1497.0021 / 1496.9989

Table 3: First Set of Frequency Readings for Experiment on Cavity 2 with Gear Box and Without Gear Box

Figure 5: Frequency Sensitivity for Test1 on Cavity 2

Backlash at the beginning of the experiment is 38000 steps. Backlashat 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.

  1. Second Test on Cavity 2

With Gear Box / Without Gear Box
Initial Frequency f0 (MHz) / 1497.0021 / 1496.9981
Final Frequency ff (MHz) / 1497.0031 / 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.

Figure 6: Frequency Sensitivity for Test 2 on Cavity 2

  1. 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.

  1. 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 shouldbe done on refurbished cryomodule, such as C50-CM7, to evaluate the gearbox performance on an improved tuner mechanism.

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