of the hardware PWM generator. Of course the onboard software sees the enable
signal when asserted and stops the (software) generation. A power supply stage,
providing voltages for all digital circuits and EXP-SFTY-ADV board is included on this
Safety part: exists an isolated isle integrated onto the regulation PCB. This part takes
in the output PWM signals coming from regulation and according to its ENABLE signal
(SAFETY ENABLE) makes pulses pass/not pass on the output connector going to the
IGBT driver: exists as separate PCB. IGBT driver is the interface system between
signals coming from Safety part and the power part. This subsystem comprises an
opto-isolation isle, a conditioning part, connected to mains supply driving IGBT gates.
IGBT Module: IGBT is the actual power module comprising heatsink, fans, electrical
shield, electric power wires.
From the operator point of view system is managed by means of either remote PC like interface
connected to the PDs or using an onboard keypad. Both way operator may set/change parameters
that modify the system functions accordingly: speed, torque, position, acceleration, etc. All
functions are translated and implemented by means of a different gate command sequence
arriving to the IGBT gates.
Safety function specifications
Safety function "Safe Torque Off" used in ADL300 family assures that drives safely disable motor
movements taking off torque onto the motor.
STO function becomes active whenever either
voltage applied or open wires and no current flowing). The other way STO function is disable
(drive enabled) when both enable signals are asserted (DC 24v applied). Functional logic diagram
is shown is Table 1.
Though STO function activates when either of the mentioned signals is deactivated, STO Safety
Integrity Level cannot be guaranteed as long as both signals are not deactivated.
Whenever STO function is enabled PDS will no longer provide torque onto the motor, meaning
that motor will come to a stop safely. Time event sequence that takes motor stopped depends
onto motor inertia as shown in Figure 1. STO function only specifies times at which torque is no
longer applied onto the motor (Ttoff) and time elapsed before signal feedback assertion (Tfbk).
Table 1 Static Functional Table for Safe Torque Off Function.
Enabled (Torque off)
Enabled (torque off)
[Safety interlock block]
Enabled (torque off)
Disabled (drive operating)
are deactivated (zero