Residual Risks Of The Sto Function - Mitsubishi Electric MR-J4-10B(-RJ) Instruction Manual

13. USING STO FUNCTION

13.1.4 Residual risks of the STO function

Machine manufacturers are responsible for all risk evaluations and all associated residual risks. Below are
residual risks associated with the STO function. Mitsubishi Electric is not liable for any damages or injuries
caused by these risks.
(1) The 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. To prevent an electric shock, install a magnetic contactor or a molded-case circuit breaker to the
main circuit power supply (L1/L2/L3) of the servo amplifier.
(2) The STO function disables energy supply to the servo motor by electrical shut-off. It does not guarantee
the stop control or the deceleration control of the servo motor.
(3) For proper installation, wiring, and adjustment, thoroughly read the manual of each individual safety
related component.
(4) In the safety circuit, use components that are confirmed safe or meet the required safety standards.
(5) The STO function does not guarantee that the drive part of the servo motor will not rotate due to external
or other forces.
(6) Safety is not assured until safety-related components of the system are completely installed or adjusted.
(7) When replacing this servo amplifier, confirm that the model name of servo amplifiers are exactly the
same as those being replaced. Once installed, make sure to verify the performance of the functions
before commissioning the system.
(8) Perform all risk assessments to the machine or the whole system.
(9) To prevent accumulation of malfunctions, perform malfunction checks at regular intervals based on the
risk assessments of the machine or the system. Regardless of the system safety level, malfunction
checks should be performed at least once per year.
(10) If the upper and lower power modules in the servo amplifier are shorted and damaged simultaneously,
the servo motor may make a half revolution at a maximum. For a linear servo motor, the primary side
will move a distance of pole pitch.
(11) The STO input signals (STO1 and STO2) must be supplied from one power source. Otherwise, the
STO function may not function properly due to a sneak current, failing to bring the STO shut-off state.
(12) 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.
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