Siemens DC Contactor 3RT1024-1BB40

Model Interpretation and Basic Information

Item	Details
Complete Model	3RT1024-1BB40
Product Series	Siemens SIRIUS 3RT1 Series (Discontinued, Replacement Model: 3RT2024-1BB40)
Structural Specification	3-pole, Size S0, Screw Termination, IP20 Protection Class
Coil Voltage	DC24V (24 Volt DC)
Main Contact Configuration	3 Normally Open (3NO)
Application Category	AC-3 (Three-Phase Motor Load) 12A, 5.5kW/400V

Core Parameters of Thermal Current (Ith)
Thermal Current of Main Contacts

Current Type	Rated Value	Applicable Conditions	Remarks
AC-1 (Resistive Load) Thermal Current	40A	690V AC, 50/60Hz	Maximum allowable current for long-term operation
AC-3 (Motor Load) Rated Current	12A	400V AC, 50/60Hz	Corresponding to 5.5kW three-phase motor
DC-1 (DC Resistive Load) Thermal Current	12A	24V DC	Long-term operating current for DC circuits
DC-3 (DC Motor Load) Rated Current	8A	24V DC	Starting and operating current for DC motors

Thermal Current of DC24V Coil

Parameter	Value	Calculation Basis
Rated Coil Power	5.9W	Siemens official data
Coil Thermal Current	0.246A	I = P/U = 5.9W/24V
Coil Resistance	Approx. 97.5	R = U/I = 24V/0.246A
Coil Pick-Up/Holding Power	5.9W for both	DC coil has the same pick-up and holding power

III. Key Technical Characteristics

Load Adaptation: Suitable for controlling ≤12A resistive load or ≤8A DC motor load in DC24V circuits
Operating Temperature: -25°C ~ 60°C, adaptable to industrial environments
Mechanical Life: 3×10⁷ operations, Electrical Life (AC-3): 1×10⁶ operations
Insulation Voltage: 690V, reliable electrical isolation performance
Replacement Models and Compatibility

Preferred Replacement Model: 3RT2024-1BB40 (Siemens SIRIUS 3RT2 Series)

Identical main contact and coil parameters, with an additional 1NO+1NC auxiliary contact

Compatible mounting dimensions for direct replacement

Other Compatible Models:

Schneider: LC1D12BD (DC24V, 12A, 3NO)

ABB: A12-30-0124VDC (12A, 3NO, DC24V)

Usage Notes
DC Circuit Application: When controlling DC24V circuits, derate the main contacts for use (≤12A resistive load) and install a surge suppressor (freewheeling diode) to protect the contacts
Heat Management: Ensure adequate ventilation for the contactor, avoid enclosed installation, and further derate the load when the ambient temperature exceeds 40°C (10% derating for every 10°C rise)
Coil Protection: For the DC24V coil, pay attention to power supply fluctuations (allowable range: 21.6V~26.4V DC) to avoid burnout due to overvoltage
Mounting Method: Supports 35mm standard DIN rail mounting or panel mounting, with no restriction on mounting direction

Summary

For Siemens 3RT1024-1BB40 in DC24V circuits, the thermal current of the main contacts is 12A (resistive load) and the thermal current of the DC24V coil is approximately 0.246A. This model has been discontinued, and it is recommended to use the replacement model 3RT2024-1BB40 as the first choice, which features better performance and an added auxiliary contact function.

Siemens 3RT1024-1BB40 Selection Quick Reference Table (DC24V/Thermal Current Special)

Applicable Scenarios: Procurement Verification / On-Site Installation / Model Replacement / Parameter Review

Module	Item	Rated Parameter/Core Information	Remarks/Applicable Conditions
Basic Information	Product Model	3RT1024-1BB40	Siemens SIRIUS 3RT1 Series (Discontinued)
	Coil Voltage	DC24V (Direct Current)	Consistent pick-up/holding power
	Contact Configuration	3-pole main contacts (3NO), no auxiliary contacts	IP20 protection, screw termination
	Structural Specification	Size S0, 35mm standard DIN rail mounting	No mounting direction restriction, panel/rail mountable
Main Contact Current Parameters	AC-1 (Resistive Load) Thermal Current	40A@690V AC/50/60Hz	Maximum allowable current for AC long-term operation
	AC-3 (Motor Load) Rated Current	12A@400V AC/50/60Hz (5.5kW three-phase motor)	Rated for AC motor starting/operation
	DC-1 (Resistive Load) Thermal Current	12A@24V DC	Core parameter for DC24V long-term operation (Key Point)
	DC-3 (Motor Load) Rated Current	8A@24V DC	Adapted for DC24V motor load
DC24V Coil Parameters	Rated Power	5.9W	Siemens official rating
	Coil Thermal Current	0.246A	Calculation formula: I=P/U=5.9W/24V
	Coil Resistance	Approx. 97.5Ω	Calculation formula: R=U/I=24V/0.246A
	Allowable Voltage Range	21.6V~26.4V DC (±10%)	Avoid coil burnout from over/undervoltage
Life/Insulation	Mechanical Life	3×10⁷ operations	Industrial-grade durability
	AC-3 Electrical Life	1×10⁶ operations	Adapted for frequent motor start/stop
	Insulation Voltage	690V AC/DC	Reliable electrical isolation performance
Preferred Replacement Model	Model	3RT2024-1BB40 (Siemens 3RT2 Series)	Original factory upgraded model, direct compatible replacement
	Core Compatibility Points	Same main contact/coil/mounting dimensions as 3RT1024-1BB40	No rewiring cost, direct replacement
	Upgrade Points	Added 1NO+1NC auxiliary contacts, improved protection/durability	First choice for cost performance
Cross-Brand Compatible Models	Schneider	LC1D12BD	DC24V, 3NO main contacts, 12A@400V AC-3
	ABB	A12-30-01*24VDC	DC24V, 3NO main contacts, 12A@400V AC-3
Installation/Usage Key Points	Installation Requirements	35mm standard DIN rail, ventilated installation, avoid enclosure	Reduce temperature rise, ensure heat dissipation
	DC Protection	Install a freewheeling diode on main contacts when controlling DC24V circuits	Suppress surges, prevent contact erosion
	Temperature Derating	10% load current derating for every 10°C rise when ambient temperature ＞40℃	e.g., DC24V resistive load ≤10.8A at 50℃
	Operating Temperature	-25℃ ~ 60℃	Adapted for industrial high/low temperature environments