American Magnetics 05500PS-430-601 High Stability Integrated Power Supply System - Manual (Page 39)

Rev. 5 21
Installation
Magnets w/o Persistent Switch
magnets without a persistent switch, and 2) operation on a short-circuit or
low resistance load.
2.7 Superconducting Magnets with No Persistent Switch
An external stabilizing resistor for superconducting magnets without a
persistent switch is no longer required
1
. However, these systems do
require a specific Model 430 Programmer stability setting based on the
magnet inductance as follows:
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 60) and adjust the stability setting (see
section 3.10.2.1 on page 54) 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
1. Effective with Model 430 firmware version 1.62.