Principles of Siemens contactor selection method

Siemens contactor type and usage category

1. Use categories AC-3 and AC-4 (number of main contacts 3P, 3NO) :

● Domestic models are 3RT6, 3RT5, 3TS, 3TB, 3TF3-5 (production stop);

● Import models are 3RT10, 3RT20, 3RT12, 3TF6.

2. Use category AC-1 (number of main contacts 3P, 3NO) :

● Import models are 3RT24, 3RT14.

3. Use category AC-1 (number of main contacts 4P, 4NO) :

● Import models are 3RT23, 3RT13, 3TK1, 3TK2.

4. Use category AC-1 (number of main contacts 4P, 2NO+2NC) :

● Import models are 3RT25, 3RT15.

5. Use ac-6B (number of main contacts 3P, 3NO) :

● Import models are 3RT16, 3RT26.

6. Use category DC (number of main contacts: 2P, 2NO) :

● The imported model is 3TC4/5/78.

7. Use category DC (number of main contacts 1P, 1NO) :

● The imported model is 3TC74.

Siemens contactors use category definitions

According to the relevant standards in DIN EN 60947-4-1, the contactor's purpose and load characteristics can be expressed using the characteristic values of the class in combination with the rated operating current value or the motor power and rated voltage. Generally speaking, a contactor can be used in several different categories, but from an objective point of view, it mainly depends on the voltage, rated current and installation situation of Siemens contactor. The specific selection principles of the categories are as follows.

1. Current type: AC, use type: AC-1, typical application place: non-inductive or low inductive load such as resistance furnace.

2. Current type: AC, use type: AC-2, typical application place: starting and breaking of wound motor.

3. Current type: AC, use type: AC-3, typical application place: starting and breaking of three-phase asynchronous motor during operation.

4, current type: AC, use category: AC-4, typical application: three-phase asynchronous motor starting, reverse braking or reverse operation, inching control.

5. Current type: AC, use type: AC-6B, typical application place: on and off of capacitor group.

6. Current type: DC, use type: DC-1, typical application place: non-inductive or low inductive load, such as resistance furnace.

7, current type: DC, use category: DC-3, typical application: shunt motor starting, reverse connection braking or reverse operation, inching, resistance braking.

8, current type: DC, use category: DC-5, typical applications: series motor starting, reverse connection braking or reverse operation, inching, resistance braking.

Note: THE AC-3 allows the contactor to be used for occasional electric or reverse braking for a limited period of time, but the number of operations may not exceed 5 per minute and 10 per 10 minutes.

Siemens contactor selection parameters principles

Contactor type: the commonly used main circuits are AC and DC, which play the role of controlling the motor and switching the resistive load.

◆ Number of main circuit poles: 3 and 4 poles are commonly used in Siemens AC contactors, and 1 and 2 poles are commonly used in Siemens DC contactors.

◆ Main circuit current: When selecting the equipment, the current of contactor must be greater than the rated current of the motor, and the subsequent selection should be carried out according to the current parameters corresponding to the categories.

◆ Main circuit voltage: refers to the rated voltage and insulation voltage two-phase parameters.

◆ Control coil voltage and power consumption.

The number and capacity of auxiliary contacts.

◆ Does the installation site belong to special applications, such as special coil width voltage used in railways, etc.

◆ Is the altitude of the application site reasonable? If it exceeds the altitude, the volume reduction of the contactor shall be taken into account.

◆ Protection accessories can be properly configured to enhance safety and service life, such as surge suppressor, mechanical interlock and other devices.

◆ Finally, we should choose Siemens contactor which is made in China or imported from China.

How to select Siemens DC and AC contactor

First of all, the contactor is capable of fast switching on or off the two main circuits, namely AC and DC. Second, we should consider which type of Siemens contactor to choose according to the current type of switching on the main circuit. Ac contactors can be used when switching ac, and dc contactors can be used when switching DC.

Common rated voltages for Siemens contactors

◆3TF series: 3TF45 or below with rated voltage of 690V. The rated voltage of 3TF46 and above is 1000V.

◆3RT series: Contactor in S00, S0, S2, rated voltage 690V. For the s3-s12 contactor, the rated voltage is 1000V.

Siemens contactor coil voltage selection

The coils of the 3TF contactor can be selected according to the voltage type (AC or DC), frequency (50Hz or 60Hz) and voltage value of the control circuit. Usually the eighth and ninth digits in the article number are the coil voltage specifications, with OX for AC and 1X for DC. At the same time, the 10th and 11th are codes representing the coil voltage class. The specific coil voltage selection table is shown in the figure below.

Siemens contactor high altitude capacity reduction principle

When the equipment is applied to the plateau, capacity reduction measures shall be taken after reaching 2,000 meters. The specific capacity reduction coefficient is shown in the figure below.

Siemens contactor for special applications