American Magnetics 4Q1005PS-430 Integrated Power Supply System - Manual (Page 158)

140 Rev. 5
Service
Troubleshooting Hints
5.2.10 Cannot place the magnet in persistent mode.
Ensure there is adequate LHe level in the cryostat to allow the
persistent switch to cool to the superconducting state.
5.2.11 Cannot bring the magnet out of persistent mode.
1. If a PSwitch Error was indicated when the PERSIST. SWITCH
CONTROL key was used to turn on the persistent switch heater
current, then there is a problem with the wiring to the persistent
switch heater. Check the continuity between the persistent switch
heater power supply output pins at the rear panel MAGNET
STATION CONNECTORS and the connectors on the magnet
support stand top plate. Refer to Table A-1 on page 145.
2. Verify that the output of the persistent switch heater is set to the
appropriate value. Refer to section 3.10.2.8 and Figure 3-13 on page
73.
3. Ensure that there is sufficient time for the switch to warm before
the power supply current is changed. Increase the persistent switch
heating time if needed. Refer to section 3.10.2.9.
5.2.12 The magnet quenches for no apparent reason
1. Ensure the magnet is not being charged at a ramp rate exceeding
the capabilities of the magnet. Exceeding the designed rate for
ramping the magnet may cause a quench or it may turn on
protective diodes on the magnet which may appear very similar to a
quench.
2. Ensure there is adequate LHe level in the cryostat. For systems
operating at less then 4.2K, ensure the magnet is cooled to the
temperature specified by the magnet manufacturer.
3. For conduction-cooled magnets, ensure the magnet temperature is
proper and in accordance with the magnet manufacturer’s
specifications.
4. Disable the Model 430 Programmer quench detection feature (see
section 3.15.2 on page 88) if you suspect the Model 430 Programmer
is falsely indicating a quench condition.
5.2.13 Cannot lower the magnet field
1. Ensure the magnet is not in the persistent mode. Refer to section
3.13.3 for the procedure to remove a magnet from the persistent
mode of operation.