American Magnetics 05100PS-430-601 High Stability Integrated Power Supply System - Manual (Page 37)

Rev. 3 19
Installation
Operation on a Short-Circuit
For magnet inductance <= 100 Henries (H):
Stability Setting = (100 - H)
For magnet inductance > 100 Henries:
Stability Setting = 0
2.8 Short-Circuit or Resistive Load
If operating with a short-circuit as a load without the presence of a
superconducting magnet, the Model 430 Programmer must be manually
configured for stability. Normally, when the persistent switch heater is
deactivated, the Model 430 Programmer sees essentially a short-circuit
load since the persistent switch shunts all current flow away from any
connected magnet. Therefore, one method of operating a short-circuit is to
indicate that a persistent switch is present, with the persistent switch
heater deactivated.
The preferred method is to indicate that a persistent switch is not present
(see section 3.10.2.6 on page 58) and adjust the stability setting (see
section 3.10.2.1 on page 52) to control the load. A stability setting of 100%
will always allow control of a short-circuit as the load, regardless of the
state of the persistent switch heater.
If the resistance of the load is increased, the stability setting must be
decreased to improve the transient response of the system. If the current
appears to lag, then decrease the stability setting until the system is
responsive. If the current appears to oscillate, increase the stability setting
until the oscillations are damped.
Note
If you have purchased a superconducting magnet with the Model
430 Programmer, AMI will normally provide a recommended
stability setting for optimal operation of the magnet system. If you
operate the Model 430 Programmer with a different load, be sure to
restore the stability setting to the recommended value when the
superconducting magnet is reconnected.
The stability setting is essentially manual control of the gain of an
integrator present in the control logic of the Model 430 Programmer.
Increasing the stability setting decreases the gain of the integrator.
A special case is with the energy absorber designs available from AMI. The
Model 601 Energy Absorber is a nearly infinite-resistance device until 5
Vdc is achieved across its terminals. Once the 5 Vdc “bias” is present, the
Model 601 allows current flow with a nominal 2 mΩ series resistance.
Therefore, the Model 430 Programmer will require an “integration time” to