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(4) Shut-off function (STO, SS1)
• STO function disables energy supply to the servo motor by electrical shut-off. The
function does not mechanically disconnect electricity from the motor. Therefore, it
cannot prevent exposure to electric shock, install a magnetic contactor or a molded case
circuit breaker to the main circuit power supply (L1, L2, and L3) of the servo amplifier.
• STO function can disable the energy to servo motor by the electrical shutoff. This
function does not guarantee the procedure of stopping the servo motor and deceleration
control.
• SS1 function only guarantees the delay time before STO becomes effective.
• If SS1 delay time is shorter than servo motor deceleration time, or forced stop function
has an error, STO becomes effective during motor rotation, dynamic brake stop or
free-run stop is activated.
• Even if STO function becomes effective with a STO switch, voltage may be left in the
servo amplifier and servo motor due to the inherent delay of the equipment.
• When the servo amplifier is replaced, make sure that new one is the same type as the
old one. After installation, make sure to check the performance of safety function before
operating the system.
• Check the safety at a certain cycle which is defined by the safety standard to prevent
the accumulation of failures. Check the safety at least once a day regardless of system
safety level.
• If a power module of a servo amplifier shorted at the upper and lower positions, the
servo motor axis rotates half at maximum. For a linear servo motor, the primary side will
move a distance of pole pitch.
• Make sure to supply STO input signals (STO1, STO2) from one power supply.
Otherwise, the STO function may not function properly due to a sneak current, failing to
bring the STO shut-off state.
• For the STO I/O signals of the STO function, supply power by using a safety extra low
voltage (SELV) power supply with the reinforced insulation.
(5) Standstill monitoring (SS2, SOS)
• The position dependent safety function (SOS) is based on two independent
safety-related sensors. One of them is part of the motor, which has a built-in encoder
(for functional motion control); the other must be provided by the customer's application
(e.g. an external sensor, PLG).
• During Safe Operating Stop, make sure that monitoring status is effective by small
oscillation before a certain period of time (about one hour) elapses in the stop status.
However, an error cannot be detected in the check interval. (The derivation of failure
until next check cannot be detected.) If stop time becomes long, use Safe Brake Control
(SBC) as mechanical rock or perform Safe Torque Off (STO).
• Avoid the continuous use of Safe Operating Stop (SOS) for eight hours or more to
prevent the accumulation of failure. If stop time becomes long, stop the break (SBC) by
mechanical rock or perform Safe Torque Off (STO).
• Encoder position feedback data does not guarantee the range out of the small
oscillation. Therefore, make sure that motor encoder feedback position can operate
normally in the machine mobile region. At least, the performance check of motor mobile
region is required.
• The position assurance of the motor with SOS is 1.75 pulses with the external auxiliary
input pulse conversion.
(6) Safe Brake Control (SBC)
• This function guarantees only that power to mechanic break is properly supplied.
Abrasion of the brake cannot be detected. Make sure regularly if the mechanic brake
can operate.
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