How to use SIRIUS 3RN2 relay to protect the motor from overheating

Motors, especially those running in explosion-proof areas, are very important to protect them from overheating. Overheating protection can be divided into two ways:

A thermal relay is connected in series in the main circuit of the motor. When the motor is overloaded, the metal sheet inside the thermal relay is thermally expanded to trigger the protection circuit. This method is suitable for motors without internal temperature detectors;

Some motors have integrated thermal resistors, which can accurately reflect the actual temperature of the motor windings. In this case, thermistor motor protection relay can be used;

Today in this article, we will introduce how to use Siemens SIRIUS 3RN2 series motor overheat protection relay.

Encoder|Transmitter|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

3RN2 is a new generation of Siemens thermistor motor protection relay, the name of the previous generation is3RN1.

Siemens 3RNx series relays can be directly connected to the A-type PTC thermistor embedded in the motor windings, and by detecting the resistance of the PTC thermistor to determine whether the motor is overheated, so as to provide more accurate protection for the motor.

PTC here is the abbreviation of "PositiveTemperature Coefficient" in English, that is, "positive temperature coefficient". With a "positive temperature coefficient" thermistor, its resistance becomes larger as the temperature increases, and becomes smaller as the temperature decreases. We take 3RN2012-1BW30 as an example to introduce SIRIUS's motor thermal protection relay.

The appearance of 3RN2012-1BW30 and the schematic diagram of the terminal structure are as follows

Encoder|Transmitter|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

The relay has a manual reset/test button and the following terminals: Working power terminal:

A1+/A2-, voltage range:

24V~240V AC/DC;

Thermal resistance terminal: T1/T2;

External reset terminal: Y1/Y2;

Two groups of CO output contacts; each group of "CO" contacts is composed of a moving contact and two static contacts, the moving contact and one of the static contacts form a normally closed contact (NC), and the other one The static contact forms a normally open contact (NO), as shown in the figure below:

Encoder|Transmitter|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

The relay has two LED indicators: READY indicates that the relay is ready; TRIPPED indicates that the relay is triggered due to short circuit, overload, or open circuit;

When 3RN2012-1BW30 is powered on (A1/A2 is energized), the contacts will act briefly (TRIPPED light flashes and then goes out), then the normally open contact is closed, the normally closed contact is disconnected, and the relay is in normal working condition ; If the T1/T2 loop resistance is less than 1500 ohms, the relay will work normally and will not be triggered; when the loop resistance is greater than 3300 ohms, the relay will be triggered, the normally open contact is disconnected, and the normally closed contact is closed; the triggered relay It can be reset by manual button or external button; the relay can also detect the short circuit and open circuit of the circuit. The working sequence diagram is shown in the following figure:

Encoder|Transmitter|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

When in use, connect T1/T2 to the thermal resistance of the motor, connect A1/A2 to the power supply (24VDC), and select a normally closed contact (such as 11-12) to connect to the digital input channel of the PLC. In this way, when the relay is working normally, the input signal of the channel is 0; when the relay is triggered, the input signal of the channel is 1; by judging the signal value of the digital input channel, it is possible to detect whether the motor is overheated and implement protection.

Well, about SIRIUS 3RN2 thermal resistance motor overheating protection relay, let’s first introduce it here.