ABB ACS880-01 Series, Инструкция по применению, Страница: 23 / 46

Protection relays
The protection relay monitors the motor equipped with temperature sensors. The sensor
indicates the motor temperature for the protection relay. For example, with a PTC thermistor,
when the motor temperature reaches the wake-up level of the sensor, the resistance of the
temperature sensor increases sharply. The relay detects the change and indicates motor
overtemperature through its output contacts. The opening contacts open the STO circuit of
the drive. This disconnects the power supply from the motor.
Use an ATEX-compliant protection relay only. The example uses an ABB CM-MSS.41
thermistor motor protection relay. You can find more information in the CM-MSS.41 data
sheet (2CDC112216D0201 [English]). In this thermistor relay, it is possible to implement a
manual reset.
Include the protection relay test to the start-up and acceptance test of the motor thermal
protection circuit. See the relay documentation for the relay tests.
Wiring
When you install the motor thermal protection circuit, keep the switching (safety) signal
isolated from all other signals.
￭ Insulation of the sensor circuit
When you connect the temperature sensor(s) of the Ex motor to the drive STO terminals
through a relay, make sure that there is reinforced (double) insulation between the main
circuit (motor) and the drive control unit as required by IEC 61800-5-1. The insulation of the
temperature sensor in the Ex motor and the insulation of the protection relay form the
insulation of the whole circuit. All Ex motors manufactured by ABB have basic insulation
between the main circuit and the temperature sensor.
￭ General wiring instructions
1. Install only the sensor circuit into the potentially explosive atmosphere.
The sensor circuit in the Ex Zone must comply with the requirements for the applicable
type of protection, such as:
• Ex d (EN/IEC 60079-1)
• Ex eb (EN/IEC 60079-7, Ex e in EN 60079-7:2007 and IEC 60079-7:2006)
• Ex ec (EN/IEC 60079-7, Ex nA in EN/IEC 60079-15:2010).
2. Install the drive or inverter unit, including the components of the ATEX-certified motor
thermal protection function, outside the potentially explosive atmosphere.
3. For the sensor connection, ABB recommends to use shielded twisted-pair cable. This
type of cable decreases electromagnetic interference in the sensor circuit.
4. Route the sensor cables away from the motor cable. Power cables can cause
electromagnetic interference in the sensor circuit.
5. Ground all sensor cable shields to a single grounding point outside the potentially
explosive atmosphere. 360-degree grounding of the cable shields is recommended. Do
not connect the cable shields to ground at the sensor end of the cable.
6. Connect the control cable shields to the chassis only.
Implementing a motor thermal protection circuit 23