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VLT® PTC Thermistor Card MCB 112
Operating Guide
FC 302 with firmware version V6.3x or higher, FC 102 with firmware version V4.40 or higher, and FC 202 with firmware version V2.63
or higher are equipped with an ATEX ETR thermal monitoring function for operation of Ex eb and Ex ec motors according to EN
60079-7. Combined with an ATEX-approved PTC monitoring device like the MCB 112, the installation does not need an individual
approval from an approbated organization, so there is no need for a specific matched-pairs approval.
The ETR Thermal Monitoring feature makes it easier to apply Ex eb and Ex ec motors instead of the more expensive, larger, and
heavier Ex db motors. The use of Ex eb and Ex ec motors is possible by ensuring that the drive limits the motor current to prevent
the motor from heating up.
1.5.5 Tripping Function
The VLT
PTC Thermistor Card MCB 112 includes a tripping stage for PTC thermistor sensors with safe potential separation of supply
®
voltage from ground. The tripping function switches off the +24 V DC directly at terminal 37 on the drive.
The PNP logic output terminal X44/10 signals the status in case of failure. The MCB 112 works according to the closed-circuit princi-
ple. The device trips in case of short circuit or line interruption.
1.5.6 Safe Separation
The PTC thermistor circuit (T1, T2) has a safe separation of low-voltage electric circuits (PELV, see
Wires.
1.5.7 Safe Disconnection Principle
The Safe Torque Off function disables the control voltage of the power semicondictors or the drive output stage. Disabling the con-
trol voltage prevents the inverter from generating the voltage required to rotate the motor.
1.5.8 Safe Disconnection Principle Diagram
Non-explosive hazard zone
Drive
PTC Thermistor Card
MCB 112
+24 V
Logic
Safe stop
out
T37
DI
Control card
91
92
93
Converter module
Illustration 2: Block Diagram of Safe Disconnect with MCB 112
8 | Danfoss A/S © 2022.08
T1
T2
TP
TP
96
PTC-sensors
97
98
3~Ex-Motor
Potentially explosive
atmosphere
Introduction
3.4 Connecting Sensor Circuit
AQ267038105120en-000101 / 130R0104
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