C7-350A DC Contactor

Product Introduction

The BSB C7-350A DC contactor is a heavy-duty high voltage DC contactor designed for high current switching in electric vehicles, battery energy storage systems (BESS), and photovoltaic (PV) control applications. With a continuous current rating of 350A and a sealed epoxy housing rated IP67, it offers long life, superior arc suppression, and safe operation in extreme environments. The contactor supports both 12/24VDC and 48/72VDC coil configurations, and optional auxiliary contacts are available.

Product Features

• High Continuous Current: Rated for 350A continuous current and 2500A switching at 320VDC.

• Low Resistance Design: Maintains ≤0.2 mΩ contact resistance for low heat and energy loss.

• Fully Epoxy-Sealed: IP67 protection for dust, moisture, and gas-tight performance.

• Wide Coil Voltage Range: Available in 12/24VDC and 48/72VDC options with economizer.

• Flexible Mounting & Contact Options: Vertical or horizontal mounting; NO, NC, or changeover auxiliary contacts optional.

• Capacitive Load Ready: Supports capacitive load switching up to 600A with proper pre-charge.

• Vibration Tested: Designed for 20G vibration and 50G shock endurance.

Typical Applications

• EV powertrain systems with 350A load requirements

• Large BESS pre-charge, discharge, and protection

• Photovoltaic combiner boxes or inverter output switching

• High-voltage marine or military-grade DC control panels

• Heavy machinery and off-highway electric vehicles

Summary of Technical Parameters

Dimensional Drawing & Wiring Diagram

Vertical type with economizer

Horizontal type with economizer

FAQs About The BSBC7-350A DC Contactor

Q1: Does the C7-350A DC contactor have reverse surge protection?
A1: Only products equipped with a PWM economizer include a surge suppression circuit. If you choose a standard product without an economizer, you need to address the issue of counter-electromotive force (back EMF) from a design perspective.

Q2: Is the C7-350A DC contactor compatible with 1000V systems?
A2: Yes. It’s rated for up to 1000VDC and built with insulation grade Ui=1000V, dielectric strength AC 3000V.

Q3: What is the recommended conductor size?
A3: A minimum cross-sectional area of 120mm² is required for safe and efficient current flow.

Precautions for Use

To ensure optimal operation and reliability of the C7-350A high voltage DC contactor, please follow the precautions below:

Mechanical Installation

• Always use spring washers during installation to prevent screw loosening.

• Tighten the screws with a torque of 2.5–3.5 N·m as specified. Exceeding the maximum torque may cause the product to break.

• Do not use the contactor if it has been dropped or subjected to impact, even if no visible damage is observed.

Wiring and Polarity

• The main contacts and control coil leads are non-polarized, meaning there are no polarity requirements for wiring.

• Ensure that the external terminal has reliable contact with the main terminal, and avoid contamination with grease or debris that could cause overheating.

Coil Surge Protection

• For products with economizer, a built-in reverse surge absorption circuit is included, eliminating the need for an external surge protector.

• For products without economizer, install a varistor or TVS diode rated at 1.5–2 times the coil voltage at the coil terminals for surge protection.
  ⚠️ Avoid using diodes as they may reduce the product’s breaking capacity.

Environmental Conditions

• Operating temperature range: -40°C to +85°C

• Avoid placing the contactor near a strong magnetic field (e.g., near transformers or magnets) or near heat-emitting components (e.g., fuses, shunt resistors).
  ➤ If installation near a heat source is unavoidable, perform a temperature rise test to confirm the acceptable temperature range and prevent overheating.

• Altitude limit: ≤4000m

• IP rating: IP67 (sealed inner space)

Switching and Life Expectancy

• This contactor is a high-voltage DC switch with a defined switching life. Once it reaches its electrical life limit, it may lose its ability to disconnect properly.

• Do not exceed the rated switching capacity or the contactor’s lifetime.
  ➤ It is strongly recommended to design the circuit to cut off power within 1 second in case of failure or sticking.

Load Conditions

• For resistive loads, the rated current and voltage can be applied directly.

• For inductive loads (L/R > 1ms), an inrush current protection device such as a TVS diode or varistor must be installed in parallel.

• For capacitive loads, a pre-charge circuit should be used to prevent high inrush current from causing contact welding.

Coil Drive and Switching Behavior

• If the coil and main contacts are repeatedly energized and de-energized at full load and rated voltage, the coil temperature will rise, increasing resistance and required pull-in voltage.
  In this case, take one or more of the following actions:

  • Reduce load current

  • Limit continuous “on” time

  • Use a coil voltage higher than the rated pull-in voltage

• The coil drive power must exceed the coil’s rated power to ensure reliable operation. Failure to do so may result in reduced contactor performance.

• For models with energy-saving circuits, the coil will automatically switch to holding power mode about 0.1s after power-on.
  ⚠️ Do not attempt to switch off during this moment, as it may damage the internal coil.

Others

• 🔙 Back to C7 Series DC Contactors

• 📄 Download the C7-350A Specification PDF

• 📚 Learn more about DC Contactors & Relays