Vacon optbj, Safety Manual

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Thermistor function (ATEX) vacon • 45
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8
8.1 Technical data
8.1.1 Functional description
The thermistor supervision circuit of the OPTBJ board is designed to provide a reliable way of dis-
abling the drive modulation in case there is an overtemperature at the motor thermistor(s).
By disabling the drive modulation, the feeding of the energy to the motor is prevented and a further
heating up of the motor due to this is avoided.
The thermistor supervision circuit meets the requirements in the ATEX directive by directly activat-
ing the "STO" safety function of the VACON
®
100 family (See Figure 15 ) and thus provides a reliable,
software and parameter independent way of preventing the energy supply to the motor.
8.1.2 Hardware and connections
See Chapter 5.3.5 .
The thermistor (PTC) is connected between the terminals 28(TI1+) and 29(TI1-) of the OPTBJ board.
The optocoupler isolates the thermistor inputs from the control board potential
* If 230VAC is used as control voltage from the output relays, the control circuitry must be powered with a separate isolation transformer
to limit short circuit current and overvoltage spikes. This is to prevent the welding on the relay contacts.
Figure 17. Typical characteristics of a motor-protection sensor as specified in DIN 44081/DIN
440
8.1.3 Atex function
When drive is connected to the main power and if the motor temperature is below overtemperature
limits (see
Figure 17 ), the drive goes to ready state. The motor may start after a valid start com-
mand.
If the motor temperature is above the overtemperature limits (see Figure 17 ), fault 29 (Atex therm-
istor) is activated.
When the resistance of the thermistor(s) mounted in the motor goes above 4 kOhm due to motor
overheating, the drive modulation is disabled within 20ms.
According to Figure 17 , when the temperature falls below 2 kOhm, the thermistor function allows
fault reset and entering to ready state.
OPTBJ:
OPTBJ:
OPTBJ
11580_uk