GFK-3111A PACMotion VFD AC Variable Speed Drive User Guide 37
What STO Does Not Provide
WARNING
Disconnect and ISOLATE the drive before attempting any work on it. The “STO” function does not prevent
high voltages from being present at the drive power terminals.
WARNING
1
NOTE The “STO” function does not prevent the drive from an unexpected re-start. As soon as the “STO”
inputs receive the relevant signal it is possible (subject to parameter settings) to restart automatically. Based
on this, the function should not be used for carrying out short-term non-electrical machinery operations
(such as cleaning or maintenance work).
WARNING
2
NOTE In some applications additional measures may be required to full the systems safety function needs:
the “STO” function does not provide motor braking. In the case where motor braking is required a time delay
safety relay and/or a mechanical brake arrangement or similar method should be adopted, consideration
should be made over the required safety function when braking as the drive braking circuit alone cannot be
relied upon as a fail-safe method.
WARNING
When using permanent magnet motors and in the unlikely event of multiple output power devices failing then the
motor could effectively rotate the motor shaft by 180/p degrees (Where p denotes number of motor pole pairs).
“STO” Operation
When the “STO” inputs are energised, the “STO” function is in a standby state, if the drive is then given a
“Start signal/command” (as per the start source method selected in P1-13) then the drive will start and
operate normally.
When the “STO” inputs are de-energised then the STO Function is activated and stops the drive (Motor will
coast), the drive is now in “Safe Torque Off” mode.
To get the drive out of “Safe Torque Off” mode then any “Fault messages” need to be reset and the drive
“STO” input needs to be re-energised.
“STO” Status and Monitoring
There are a number of methods for monitoring the status of the “STO” input, these are detailed below:
Drive Display
In Normal drive operation (Mains AC power applied), when the drives “STO” input is de-energised (“STO”
Function activated) the drive will highlight this by displaying “InHibit”.
NOTE If the drive is in a tripped condition then the relevant trip will be displayed and not “InHibit”.
Drive Output Relay
• Drive relay 1: Setting P2-15 to a value of “13” will result in relay opening when the “STO” function is activated.
• Drive relay 2: Setting P2-18 to a value of “13” will result in relay opening when the “STO” function is activated.
Table 22: “STO” Fault Codes
Fault Code Code Number Description Corrective Action
“Sto-F” 29
A fault has been detected within either of
the internal channels of the “STO” circuit.
Refer to your Emerson Sales
Partner
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