JVL MIS17 Series User Manual page 72

3.4
3.4.13 Service and maintenance
For PL e or SIL3, it is a must, for lower PL or SIL it is recommended to conduct a func-
tional test every 12 months to detect any failure or malfunction of the STO functionality.
To conduct the functional test, perform the following steps (or a similar method suitable
for the application):
1. Remove the 24 V DC voltage supply from the STO A and B.
2. Check if the monitoring gives an error message.
3. Verify that the motor is coasting and comes to a complete stop.
4. Verify that the motor cannot be started by re-applying the 24 V DC to STO A and B.
5. Verify that the motor is not started automatically until errors are cleared and the mo-
tor is set in an active mode.
3.4.14 Capabilities
Safe Torque Off performs a safety function such that when one of the STO inputs is not
active, (i.e. open-circuit or set at nominally 0V), the motor will not develop torque. The
STO function is implemented purely in simple solid state hardware for which substantial
failure data exists, allowing meaningful quantitative FMEA to be carried out. The function
does not use software or complex hardware. The probability of failure of the safety func-
tion due to a hardware fault has been estimated by JVL Industri Elektronik A/S as 1,38e-
10 per hour (IEC61508/IEC62061/IEC61800-5-2) or 4,29e-8 per hour (ISO13849), and
assessed by the independent notified body TÜV NORD (pending). The input is compat-
ible with self-testing digital outputs of controllers such as PLCs, where the test pulse is a
maximum of 1 ms. This means that the drive is not disabled by logic-low input pulses with
a maximum of 1 ms duration.
3.4.15 Limitations
• STO uses solid-state techniques, it does not provide physical separation of electrical
connections and is not intended to provide electrical isolation.
• STO does not provide braking, it disables the motor so no motor electrical braking
is available. If motor braking is a requirement then an external arrangement must be
made to stop the motor conventionally and then to safely remove the STO inputs to
activate STO. Braking by the drive is not a high-integrity function, if braking is a safety
requirement then an independent fail-safe brake must be provided.
72 JVL Industri Elektronik A/S - User Manual - Integrated Stepper Motors MIS17x, 23x, 34x, 43x
Commissioning
Option