Lake Shore 625, User Manual, Page: 43 / 132

Lake Shore Model 625 Superconducting MPS User’s Manual
Operation 4-7
4.7 COMPLIANCE VOLTAGE LIMIT
The output compliance voltage limit of the Model 625 can be set between 0.1 and 5 V. The setting is in magnitude only
and will limit both positive and negative voltages.
On most superconducting magnets, the maximum compliance voltage is usually stated and can vary depending on the
current in the magnet. Exceeding the maximum compliance voltage of the magnet can cause the magnet to quench. The
compliance voltage can be limited by setting the maximum compliance voltage setting. Refer to Paragraph 4.11 to setup
the maximum settings.
To change the compliance voltage limit press the Voltage Limit key. The compliance voltage limit value on the normal
display will be highlighted to prompt for the new compliance voltage limit value.
V Limit: 5.0000 V
Use the data entry keys to enter the compliance voltage limit value between 0.1000 and 5.0000 V. Press Enter to accept
the new value. Press Escape to restart the setting sequence and enter a different value. Press Escape again to leave the
setting sequence.
4.8 ZERO OUTPUT CURRENT
The Zero Output key on the front panel can be used to set the output current setpoint to 0 A. The current output will
then begin to ramp down using the current ramp rate. This key is equivalent to using the Output Setting key and
entering 0 A. Refer to Paragraph 4.5 to set the output current. There are certain circumstances in which the current will
not be allowed to change, just like when entering a new output current setpoint. An error box will pop up explaining why
the current is not allowed to change. These error boxes are described in Paragraph 4.5
4.9 STOP OUTPUT CURRENT
The Stop Output key will stop the output current ramp within two seconds after the key is pressed even if the magnet is
ramping against the compliance voltage. A new output current setpoint must be entered for the output current to begin
ramping again.
4.10 PAUSE OUTPUT CURRENT
The Pause Output key will pause the output current ramp within two seconds after the key is pressed. While the output
current ramp is paused, the Ramping LED will blink. Pressing the Pause Output key while the output current ramp is
paused will cause the output current ramp to resume ramping to the original output current setpoint.
4.11 MAXIMUM SETTING LIMITS
The Model 625 offers maximum setting limits for output current, compliance voltage limit, and output current ramp rate.
Typically the properties of the superconducting magnet will dictate what these maximum settings should be. Exceeding
the maximum settings stated by the magnet manufacturer can cause the magnet to quench or be damaged. These
maximum settings should be entered before the magnet system is used to prevent a quench if a setting is incorrectly
entered. Note that the maximum settings will only limit the value when a new setting is entered. For example, if a
maximum ramp rate limit is entered that is less than the present ramp rate, the present ramp rate will not be limited until
a new ramp rate is entered.
4.11.1 Maximum Output Current
The maximum output current limits, in magnitude, the maximum output current that can be entered. This setting will
only limit the internal output current setting. If the output current is being programmed by an external voltage, then some
provision must be made to insure that the programming voltage will never exceed the desired output current. See
Paragraph 4.18 to setup the External Programming mode.