Safe Torque Off (Sto) - Kollmorgen AKD Série Guide De Sécurité

1.4.7 Safe Torque Off (STO)

The STO safety implementation on the AKD is certified. The safety circuit implementation
used for the safety function "Safe Torque Off" in the drive is suited for SIL 2 according to IEC
62061 and PLd / CAT3 according to ISO 13849-1. SIL3/PLe is possible with AKD-x04807
drives, if both STO-Enable inputs and the corresponding STO-Status signals are used.
AKD-x003 up to AKD-x024: An additional digital input (STO) releases the power output
stage of the drive as long as a 24 V signal is applied to this input.
AKD-x048: Two additional digital inputs (STO-Enable 1 and STO-Enable 2) release the
power output stage of the drive as long as a 24 V signal is applied to these inputs.
If the STO input goes open-circuit, then power will no longer be supplied to the motor, and the
drive will lose all torque and coast to a stop.
1.4.7.1 Important Notes
WARNING
The drive cannot hold a vertical load when STO is active. Serious injury
could result when load is not properly blocked. Drives with a suspended
load must have an additional safe mechanical blocking (for instance, by a
motor-holding brake).
CAUTION
The STO function does not provide an electrical separation from the
power output. There is a danger of electrical shock and personnel injury! If
access to the motor power terminals is necessary, the drive must be dis-
connected from mains supply considering the discharging time of the inter-
mediate circuit.
CAUTION
In case of a specific double fault within a very short timea single move-
ment of maximum an angle of 120° (electrical) can happen. This effect can
only happen if the drive is in the function STO.
If the safety function STO is automatically activated by a control system, then make sure
that the output of the control is monitored for possible malfunction. The monitoring can be
used to prevent a faulty output from unintentionally activating the STO function. Since the
STO function is a single-channel system, erroneous engaging will not be recognized.
It is not possible to perform a controlled brake if the drive controlled STO-Enable is off. If con-
trolled braking before the use of the STO function is necessary, the drive must be braked and
the input STO must be separated time-delayed from +24 V .
Use the following functional sequence when the STO function is used:
1. Brake the drive in a controlled manner (speed setpoint = 0 V).
2. When speed = 0 rpm, disable the drive (enable = 0 V).
3. If a suspended load is present, block the drive mechanically.
4. Activate the STO function.
AKD Safety Guide | 1 English
Kollmorgen | kdn.kollmorgen.com | December 2015 17