Safe Stop; Safe Torque Off Operation; Safe Torque Off Operation (Fc 302 Only); Liability Conditions - Danfoss VLT AutomationDrive FC 300 Design Manual

Product Introduction
ETR (Electronic Thermal Relay)
At lower speeds, the ETR cuts off at lower levels due to
reduced cooling of the motor. In that way, the motor is
protected from being overheated even at low speed. The
3 3
ETR feature calculates the motor temperature based on the
actual current and speed. The calculated temperature is
visible as a readout parameter in 16-18 Motor Thermal in
the FC 300.
t [s]
2000
1000
600
500
400
300
200
100
60
50
40
30
20
10
1.0
Figure 3.39 ETR Example

3.12 Safe Stop

3.12.1 Safe Torque Off Operation

The FC 302 is available with Safe Torque Off (STO)
functionality via control terminal 37. STO disables the
control voltage of the power semiconductors of the
frequency converter output stage, which in turn prevents it
from generating the voltage required to rotate the motor.
When the Safe Torque Off (T37) is activated, the frequency
converter issues an alarm, trips the unit, and coasts the
motor to a stop. Manual restart is required. The Safe
Torque Off function can be used for stopping the
frequency converter in emergency stop situations. In the
normal operating mode when Safe Torque Off is not
required, use the frequency converter's regular stop
function instead. When automatic restart is used, the
requirements according to ISO 12100-2 paragraph 5.3.2.5
must be fulfilled.
62
1.2 1.4 1.6 1.8 2.0
Danfoss A/S © Rev. 2014-02-10 All rights reserved.
Design Guide
3.12.2 Safe Torque Off Operation (FC
The Safe Torque Off function of FC 302 can be used for
asynchronous, synchronous, and permanent magnet
motors. It may happen that 2faults occur in the frequency
converter's power semiconductor. When using synchronous
or permanent magnet motors, this may cause a residual
rotation. The rotation can be calculated to Angle=360/
(Number of Poles). The application using synchronous or
permanent magnet motors must take this into consid-
eration and ensure that this is not a critical safety issue.
This situation is not relevant for asynchronous motors.

3.12.3 Liability Conditions

Liability conditions
fOUT = 1 x f M,N
The user is responsible for ensuring that personnel know
fOUT = 2 x f M,N
how to install and operate the Safe Torque Off function by:
fOUT = 0.2 x f M,N
•
•
IM
IMN
•
The user is defined as integrator, operator, service, and
maintenance staff.

3.12.4 Additional Information

For more information regarding Safe Torque Off, including
installation and commissioning, refer to the Operating
Instructions VLT
302 only)
Reading and understanding the safety regulations
concerning health and safety/accident prevention
Understanding the generic and safety guidelines
given in this description and the extended
description in the Operating Instructions VLT
Frequency Converters – Safe Torque Off.
Having a good knowledge of the generic and
safety standards for the specific application
®
Frequency Converters – Safe Torque Off.
®
MG34S222