以下内容节选自
840D_FB3 2.6 页码293/818
840D_FB2 2.2.3

独立返回（Drive-independent retraction）条件：
Axes with digital 611D drives can (if configured and enabled) perform a retraction movement independently
_ Even if the control fails (sign-of-life failure detection)
_ If the DC link voltage drops below a warning threshold
_ When triggered by system variable $AN_ESR_TRIGGER
The retract movement is conducted independently by the 611D.

参数：
MD1634: LINK_VOLTAGE_RETRACT, detection for voltages below the permissible DC link voltage (MD1634: LINK_VOLTAGE_RETRACT), this signal can be defined as an internal error source for ESR. 电压低于这个值后驱动器直接产生内部报警,应该是$AC_ALARM_STAT置1, 用于N80 程序段.。MD1634 MD 1633: LINK_VOLTAGE_GEN_OFF: 震荡(generator)模式开始或退出(低于且接近600V). Cut-off threshold for generator operation, If the voltage exceeds the value set in MD1633, generator operation is exited and operation is switched back to speed-controlled operation.
MD 1631: LINK_VOLTAGE_GEN_ON : Response voltage for generator axis. from position controlled or speed-controlled mode to DC-link voltage-controlled mode.
MD 1632: LINK_VOLTAGE_GEN_HYST: Voltage step for generator control
If the voltage exceeds the value set in MD1631: LINK_VOLTAGE_GEN_ON and MD1632: LINK_VOLTAGE_GEN_HYST, the two-step control is disabled, that is, the current actual speed value is preset as speed setpoint.

During active generator operation, bit 3 “DC link generator active” is output in system variable $AA_ESR_STAT. 即电压低于MD1633时 $AA_ESR_STAT=1XXX(二进制), N90 语句使用,与 “H8” (二进制1000) 进行与运算 判断 该位是否为1。

1635: GEN_AXIS_MIN_SPEED, When values below this speed limit are detected, bit 4 “Generator speed
Note
_ Drive-independent emergency retraction is only effective if the pulse suppression bit is set to OFF in MD1612: ALARM_REACTION_POWER_ON
and MD1613: ALARM_REACTION_RESET.
1612、1613报警与报警复位 某些位 pulse suppression 需要设0。

配置要求：
The following hardware and software components are required:
1． Hardware components：
– SINUMERIK 840D with e.g. NCU 573 and MMC 103
– SIMODRIVE 611D with servo drive controls 6SN1 118-0DG... or 6SN1
118-0DH...
– Closed-loop controlled I/RF module (16kW and greater) with suitable pulse resistor module and additional capacitors for the DC link if required.
– Capacitor module (6FX2 006-1AA00) for backing up the 115-230VAC
power supply for the central controller and the operator panel front or alternatively the 24VDC power supply.
2．Software components
– System software: SW 5
– ESR option（选项功能）

还需要的外围配置：
The following points must be taken into account for configuring:
1. The electronics supply of the servo drive control must be provided by the DC link. For this, the user must connect the I/RF modules to the DC link (see Installation & Start-up Guide 611D).
2. A suitable backup system must be available for the NC and operator panel front; e.g. a capacitor module for 230V power supply or an accumulator for 24V power supply.
3. There must be a suitable backup system for supplying power to the PLC I/Os or the NCK terminal block I/Os, e.g. an accumulator.
连驱动的、连操作界面的、连PLC或NC端子的各种备用电源。

ESR is available in AUTO, JOG and MDA modes.
ESR 情况下使用急停：PLC要注意延时。
In applications where coupling and traversing movements must remain valid even in the event of an EMERGENCY STOP, this EMERGENCY STOP must be delayed long enough by the PLC for the required NC or drive-end reactions to terminate.
The IS “ESR reaction triggered” DB31, ... DBX98.7 is available as a checkback signal to the PLC.