Power Electronics SD750K, Руководство по аппаратному обеспечению и установке

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POWER ELECTRONICS SD750K
CONTROL CONNECTION
67
STO - Safe Torque Off
The STO function is defined as: Power, that can cause rotation, is not applied to the motor. The frequency
converter will not provide energy to the motor, which can generate torque.
For three-phase asynchronous motor, that means to stop three-phase power supply to the stator.
This function corresponds to a Category 0 Emergency Stop according to IEC 60204-1. When the drive
is running and the STO function is applied, the motor will freely stop by its own inertia.
The STO function integrated as standard in the SD750 Kompakt permits to achieve safety level SIL3
(PLe) for the safe stop function. SIL3 requires the use of an emergency pushbutton The maximum
reaction time of STO function is less than 50ms. See section “Safety Integrity Level SIL3-PLe” for
additional information.
By using this function, you can safely carry out cleaning, maintenance or emergency work on non-electric
parts of the equipment, without having to disconnect the power supply. In case STO safety function is
not used, user must connect the corresponding terminals.
Based on a study of each application and risk assessment, the designer should define the required safety
function and safety level.
CAUTION
The STO safety function does not disconnect nor the main neither the auxiliary power supply.
With STO function the drive disconnects the motor power supply. To carry out electrical
maintenance tasks, isolate the drive. Particular care must be taken with the active conductors
inside the drive.
Failure to do so could result in damage to equipment and personnel.
Do not use the STO function as a normal drive stop.
Safety integrity level SIL3- PLe
This configuration provides a highly reliable safety level. When the sensor is activated due to an
emergency situation, the STO function interrupts the power supply to the motor. The motor will stop for
its own inertia or will prevent an accidentally start.
The sensors (emergency push buttons, limit switches, etc.) must be certified as safety elements.
The value of the average probability of a dangerous failure per hour (PFH) of all elements applicable
to the safety function, must not exceed the limit of the corresponding SIL level. The installation must
be performed by trained personal with experience in functional safety.
Example 1: Safety function with automatic restart by emergency stop buttons (SIL3, PLe) . It is
mandatory that the stop button has 2 closed contacts (NC) that will be connected to the safety inputs
of the relay.