3-16 BOP HIPWR 1113153.3.3.2 UNDERSTANDING VOLTAGE AND CURRENT PROTECT LIMITSThese values are the references for the complementary channels: voltage in current mode andcurrent in voltage mode. The range for these values is between a minimum (box) value (see Fig-ure 1-3) and 1% above the rated nominal value (see PAR. 3.3.4.2). If the unit is in voltage mode,it will enter current protect mode when the load demands more current and energy than permit-ted by the ±current protect settings. Similarly, if the unit is in current mode, it will enter voltageprotect mode if the load demands more voltage and energy than permitted by the ±voltage pro-tect settings. When the protect settings are exceeded, the protection channel limits the output, aVPROTECT, CPROTECT or PROTECT (PROTECT may be seen only when external limits arein use) message is displayed at the upper right of the LCD, and the power supply continuesoperation.3.3.3.3 HIDDEN VOLTAGE AND CURRENT PROTECT LIMITSThe BOP employs two back-up channels which function as safety backups if a main channelfails. The backup channel limits are fixed and not user accessible. These limits are set to 5%over the nominal (rated) values for voltage or current. If the software limits for a main channel ischanged (PAR. 3.3.4.1) the corresponding protect channel limit is automatically changed to be5% of the nominal (rated) value above the user-programmed software limit.3.3.4 CHANGING MAXIMUM OR MINIMUM SOFTWARE-CONTROLLED LIMITSThe maximum or minimum allowable voltage and current settings of the unit can be reducedfrom the nominal using the Max/Min Settings menu (Table 3-5). which lists the system’s soft-ware-controlled voltage and current limits (+Voltage Max, –Voltage Min, +Current Max, –CurrentMin) as well as the corresponding protection limits organized by operating mode. The defaultvalues of the system limits are established by the Model: the nominal (rated) values for voltageand current and 1.01 x the nominal (rated) values for protection. The default values can bereduced by modifying the highlighted parameter. The unit will not accept local or remote com-mands that exceed the system limits. The system limits are always in effect, even when the unitis controlled by an external reference. If system limits are changed, the protection limitsmust be changed to correspond to the new system limits. As an example, changing +Volt-age Max and –Voltage Min of a BOP 36-28MG to ±3V, respectively, causes the unit to behaveas if it was a BOP 3-28MG. In this case it is important to change the +V Protect Max and –V Pro-tect Min limits (e.g., to ±3.3V, respectively) so that the load is protected when operating in Cur-rent Mode. System limits are absolute values (do not use minus sign for negative limits).The internal parameters +Current Protect Min and –Current Protect Max are displayed to com-pletely define the permissible window when operating in Voltage mode. Similarly, +Voltage Pro-tect Min, and –Voltage Protect Max are displayed to completely define the permissible windowfor voltage when operating in Current mode.
