American Magnetics 420 Power Supply Programmer - Manual (Page 80)

62 Rev. 7
Operation
Quench Detection
If the 5(6(7=(52 key is pressed to clear the quench condition or a
remote clear command is issued, the Model 420 will automatically enter
the PAUSED mode and will attempt to maintain the operating current
present at the point the quench condition was cleared.
In addition, the rear panel connector, J4, provides pins for external quench
input (see page 109 of the Appendix for the connector pinout). If the
quench input is asserted, then the Model 420 interprets this input as
indication of a quench condition and the Model 420 automatically sets the
power supply output voltage to zero and will not respond to further input
until the
5(6(7=(52 button is pressed to clear the quench detect
condition, or until the quench condition is cleared by a remote command.
The rear panel input cannot be disabled, however, it may be left
unconnected without the possibility of a generating a false quench
condition.
Note
If the external quench detection circuit continues to assert the
quench detection input of the Model 420, the
5(6(7=(52 key will
be unable to clear the quench condition.
3.5.1 Disabling Automatic Quench Detection
The automatic quench detection feature may be disabled in the load setup
submenu (see paragraph 3.2.2.7). However, the rear panel quench detect
input (connector J4) remains active.
If the automatic quench detection feature is disabled, the Model 420
attempts to limit the error, between the commanded current and the
present operating current, to a value that will not result in excessive
voltages being introduced across the magnet terminals. Under most
operating conditions this will not damage any internal protection circuits
of the magnet. If an actual quench condition occurs, the Model 420 will
follow the magnet current to zero unless the operator intervenes. If the
rear panel quench detect input (connector J4) is asserted, the Model 420
will force the power supply output to zero volts regardless of whether the
automatic quench detection is enabled or disabled.
In the event that the persistent switch becomes normal without operator
or remote activation of the switch heater control, the Model 420 will match
the magnet current and attempt to stabilize the load if the automatic
quench detection feature is disabled. If the automatic quench detection
feature is enabled, then this event will generally trigger the quench
detection logic if a difference exists between the magnet current and the
operating current of the Model 420.