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High Voltage DC Contactors for ESS and EV | 12V-1500V DC | 50A-500A | Ceramic Sealed
KRIPAL High Voltage DC Contactor - UKD-H Series
KRIPAL manufactures high voltage DC contactors in the UKC7 series for electric vehicle charging infrastructure, battery energy storage systems and DC microgrid applications. Rated for operational voltages up to 1500V DC and continuous currents from 50A to 500A, the UKC7 features a hermetically sealed ceramic arc chamber filled with hydrogen or nitrogen gas that quenches the DC arc within 10 milliseconds of contact separation, enabling reliable load-breaking at full rated voltage without external arc chutes. The contactor uses a double-break contact system with silver-tin-oxide (AgSnO2) contact tips that provide low contact resistance, high resistance to welding under short-circuit conditions, and a mechanical life exceeding 1 million operations. An energy-saving coil economizer reduces coil holding power by 80 percent after pull-in, minimizing heat generation inside sealed enclosures. The UKC7 is available with 12V, 24V and 48V DC coil voltages, with optional auxiliary contacts (1NO plus 1NC) for status feedback to the system controller. Certified to IEC 60947-4-1 for DC contactors and UL 60947-4-1 for North American applications, the UKC7 is the primary DC switching device in EV fast chargers, battery rack isolation circuits and DC bus-tie applications.
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UKD50H Fully Sealed High Voltage DC Contactor 50A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
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UKD100H Fully Sealed High Voltage DC Contactor 100A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
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UKD150H Fully Sealed High Voltage DC Contactor 150A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
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UKD200H Fully Sealed High Voltage DC Contactor 200A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
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UKD250H Fully Sealed High Voltage DC Contactor 250A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
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UKD300H Fully Sealed High Voltage DC Contactor 300A 9-36V
UKD-H series High Voltage DC Contactor is primarily designed for reliable power switching control in critical DC power systems.
Ask a QuoteHV DC Contactor Selection for Battery Storage and DC Power Systems
A high voltage DC contactor is an electrically operated switch designed to make and break DC circuits under load, using an electromagnetic coil to close the main contacts and a gas-filled sealed chamber to extinguish the DC arc when the contacts open. Unlike AC contactors that benefit from the natural current zero-crossing every 10 milliseconds (at 50 Hz), DC contactors must force the arc to extinguish by increasing the arc voltage through contact separation speed, gas cooling and magnetic blowout. The UKC7 hermetically sealed design prevents arc gases from escaping into the surrounding enclosure, which is critical in sealed battery containers where accumulated hydrogen from normal battery operation could create an explosion hazard if exposed to an unsealed switching arc. This selection guide covers current rating, coil voltage, auxiliary contacts and mounting configuration.
UKC7 DC Contactor Series Technical Specifications
Current Rating and Thermal Management
The UKC7 is rated in six frame sizes from 50A to 500A continuous thermal current (Ith) at 40 degrees Celsius ambient. The current rating is based on the contact tip cross-sectional area and the terminal connection cross-section, with thermal verification per IEC 60947-4-1 at rated current in free air for 8 hours until thermal equilibrium, with the maximum terminal temperature not exceeding 65 Kelvin above ambient. For applications inside sealed enclosures with restricted airflow, a derating factor must be applied. The UKC7 terminal design accepts copper busbar connections up to 40mm x 5mm cross-section for the 500A frame, with M10 stainless steel bolts torqued to 25 Nm. Optional silver-plated terminals are available for applications where copper oxidation over the service life could increase contact resistance.
Gas-Filled Hermetic Arc Chamber Technology
The UKC7 arc chamber is a ceramic-to-metal brazed assembly that maintains a gas-tight seal for the 20-year design life of the contactor. The chamber is backfilled with a gas mixture optimized for DC arc extinction: hydrogen for low-current applications (50-150A) due to its high thermal conductivity and rapid deionization rate, and nitrogen for high-current applications (200-500A) where the higher arc energy requires the greater thermal capacity of nitrogen to prevent chamber pressure from exceeding the ceramic burst strength. The gas fill pressure is verified by helium leak testing on every production unit, with a leak rate acceptance criterion of less than 1×10 to the minus 8 mbar-liters per second, ensuring that the gas fill remains intact for the rated mechanical life of the contactor. The sealed design also makes the UKC7 suitable for operation at altitudes up to 4000 meters where the reduced air density would otherwise compromise open-type arc chute performance.
Coil Voltage and Economizer Circuit
The UKC7 coil is available in 12V, 24V and 48V DC nominal voltages, with a pick-up voltage of 75 percent of nominal and a drop-out voltage between 10 and 50 percent of nominal. The integrated PWM coil economizer reduces coil current from the pull-in level (approximately 3 times the holding current for 100 milliseconds) to a holding level that maintains contact closure with 80 percent lower power consumption. For a 24V DC 500A contactor, the coil holding power is 4.8W, reducing the thermal load inside the enclosure and extending the coil insulation life. The economizer circuit includes reverse polarity protection and a transient voltage suppressor that clamps the coil flyback voltage to 60V, protecting the controlling PLC or BMS output transistor from inductive kickback damage when the coil is de-energized.
Bidirectional Switching and Non-Polarized Design
The UKC7 is a non-polarized contactor, meaning the main contacts can make and break DC current in either direction with equal reliability. This is critical for battery storage applications where current flows from the battery to the load during discharge and from the charger to the battery during charge, through the same contactor. The permanent magnet arc blowout system is symmetrical about the contact gap, so the arc is driven into the arc splitter plates with consistent force regardless of current direction. For EV charging applications where the DC contactor is in the charging cable path between the charger and the vehicle battery, the contactor must handle both directions of current that can occur during vehicle-to-grid (V2G) operation where the EV battery feeds power back to the grid. The bidirectional rating of the UKC7 is verified by type testing at rated current in both directions for 1000 make-break cycles in each polarity.
Specify DC Contactors for Your Application
- Application Review: Submit your DC switching requirements (voltage, current, duty cycle, enclosure type) for a recommended UKC7 model and mounting configuration.
- DC Switching Endurance Data: Request make-break endurance test reports at your specific voltage and current for reliability prediction in your system design.
- Custom Coil Options: Need a non-standard coil voltage or connector interface? Our engineering team can accommodate custom configurations for OEM volumes above 500 units.
Critical DC Switching in BESS, EV Charging and DC Microgrids
KRIPAL UKC7 high voltage DC contactors are the primary electrically operated switching device in applications where DC circuits must be remotely controlled under load, from electric vehicle fast chargers to grid-scale battery storage containers. The hermetically sealed gas-filled arc chamber enables reliable DC load-breaking at voltages up to 1500V DC in compact, sealed enclosures where open-type contactors would pose an arc flash or explosion hazard.
EV DC Fast Charger Power Delivery Contactor
A 350 kW DC fast charger uses a UKC7-500A 1000V DC contactor on the output DC bus between the power modules and the charging cable, with the contactor closing only after the charger has performed an isolation test and negotiated the charging parameters with the vehicle BMS via the CCS communication protocol. The contactor must be capable of breaking the full charging current if the vehicle commands an emergency stop or if the charger detects an insulation fault, and the UKC7 sealed design ensures that the switching arc does not escape into the charger enclosure where it could trigger the internal arc fault detection system. The 1 million mechanical operation rating supports the high switching frequency of a public charging station that may cycle 20-30 times per day, 365 days per year, over a 10-year service life.
Battery Energy Storage Rack Isolation Contactor
A 2 MWh utility-scale BESS container deploys a UKC7-250A 1500V DC contactor per battery rack as the main isolation device between the rack DC bus and the container-level DC combiner bus. The contactor is controlled by the BMS, which opens the contactor within 50 milliseconds of detecting a cell over-voltage, under-voltage, over-temperature or over-current condition, isolating the affected rack before the fault propagates to adjacent racks. The hermetically sealed chamber is critical in this application because battery racks generate trace hydrogen during normal operation, and an unsealed switching arc could ignite a flammable hydrogen-air mixture inside the container. The non-polarized design handles both charge current (into the battery) and discharge current (out of the battery) through the same contactor with equal performance.
DC Microgrid Bus-Tie Contactor
DC microgrids serving data centers, commercial buildings and industrial facilities use UKC7 DC contactors as bus-tie devices that connect or isolate different DC bus sections. For example, a data center with a 380V DC distribution system uses UKC7-500A contactors to connect the battery storage DC bus to the server rack DC bus. During a utility grid outage, the contactor closes to supply server loads from the battery, and when grid power is restored, the contactor opens after the AC-DC rectifier has synchronized its output voltage with the battery bus voltage. The coil economizer reduces the contactor’s standby power consumption to under 5W, which matters in a data center where hundreds of such contactors may be installed and their aggregate coil power contributes to the facility’s power usage effectiveness (PUE) ratio.
DC Shore Power Connection for Electric Ferries
Electric ferries and harbor vessels that recharge at dedicated shore power stations use UKC7-500A DC contactors as the main connection device between the shore-side DC charger and the vessel’s battery DC bus. The contactor must withstand the marine environment, with the sealed ceramic chamber protecting the contacts from salt-laden air and condensation that would quickly corrode open-type contactor contacts. The contactor closes only after the shore-side charger and the vessel BMS have completed an isolation monitoring test per IEC 61851-23 to confirm the DC cable insulation resistance exceeds 100 ohms per volt, and a pre-charge circuit has equalized the voltage between the charger output and the vessel battery to prevent the massive inrush current that would flow if a charged battery were directly connected to a discharged charger output capacitor bank.
DC Motor Control in Industrial Vehicles
Electric forklifts, airport ground support vehicles and underground mining vehicles use UKC7 DC contactors to switch the traction motor DC supply from the battery. The contactor must handle the motor starting inrush current (typically 3-5 times rated for 2-3 seconds on a DC series motor) and the inductive flyback voltage when the motor circuit is opened. The UKC7-200A unit with a 500A short-time rating (60 seconds) handles motor starting without contact overheating, and the 1500V DC rating provides margin for the inductive voltage spike that can reach twice the battery voltage when the motor field collapses. The 1 million mechanical operation life supports the high switching frequency of an industrial vehicle that may start and stop its traction motor 100-200 times per shift.
Integrate DC Contactors into Your System
- Pre-Charge Circuit Design Support: Our engineers help you size the pre-charge resistor and contactor sequencing logic to prevent inrush current damage to the UKC7 contacts.
- Coil Driver Circuit Reference Design: Request our reference schematic for a robust coil driver with flyback protection, economizer control and diagnostic feedback.
- OEM Integration Program: Dedicated UKC7 contactor variants with your connector interface, coil voltage and mounting bracket for seamless integration into your product.
KRIPAL HV DC Contactor Manufacturing: Sealed for Reliable DC Switching
KRIPAL high-voltage DC contactors are manufactured in a cleanroom assembly environment where the hermetically sealed ceramic arc chamber is evacuated and backfilled with hydrogen-nitrogen gas mixture. Each contactor undergoes coil pickup and dropout voltage verification, contact resistance measurement, and dielectric withstand testing for global battery energy storage and EV charging infrastructure applications.
Hermetic Ceramic Chamber Sealing and Gas Filling
The ceramic-to-metal seal assembly is performed in a controlled-atmosphere environment. After evacuation to below 10 to the power of minus 3 Pa, the chamber is backfilled with a hydrogen-nitrogen gas mixture optimized for arc quenching in DC switching. Each sealed chamber is helium leak-tested to verify hermeticity below 1 times 10 to the power of minus 8 Pa-cubic-meters per second.
Magnetic Blowout Arc Extinguishing Design
Permanent magnets positioned outside the ceramic chamber create a transverse magnetic field across the contact gap, forcing the DC arc into an elongated path for rapid extinction. Magnet position and field strength are verified on each production batch using a Hall-effect gaussmeter to ensure consistent DC breaking performance up to the rated voltage.
Coil Economizer Circuit Integration
Each DC contactor incorporates a PWM coil economizer module that reduces holding current by up to 85 percent after pull-in. The economizer PCB is assembled in-house and functionally tested for pickup voltage (typically 70 percent of nominal), dropout voltage, and holding current before installation into the contactor body.
Contact Resistance and Dielectric Verification
Every HV DC contactor undergoes a four-wire contact resistance measurement at 100A test current with values recorded against the production serial number. A 2500V DC dielectric withstand test is performed between the main terminals and the coil circuit, and between open contacts, with leakage current monitored for any indication of insulation degradation.
Consigned Inventory Programs for HV DC Contactors
KRIPAL supports distributor inventory programs with agreed stock levels for standard DC contactor models from 12V to 1500V DC. Shipments are planned based on demand data, with scheduled replenishment to maintain stable supply and consistent fill rates.
Private Label and OEM Branding for HV DC Contactors
Laser-marked part numbers aligned with your catalog, OEM-branded packaging, and customized multilingual instruction sheets are available. Unbranded supply is provided upon request for private label production of HV DC contactors.
Multi-Region Certification and Compliance Support
CE, UKCA, and IEC 60947-4-1 UL 60947-4-1 compliance documentation is provided according to target export markets. Technical documentation files are maintained and updated in line with evolving regulatory requirements, supporting battery storage system conformity assessments.
Direct Technical Access to KRIPAL Production Engineers
Your technical team communicates with the engineers who designed and tested your HV DC contactors, not a distributor’s sales engineer reading from a catalog. Application questions receive answers within 24 hours during China business hours.
Frequently Asked Questions
Explore FAQ >HV DC contactors use hermetically sealed gas-filled chambers and magnetic blowout technology to extinguish DC arcs. AC contactors rely on the AC current zero-crossing and cannot safely interrupt DC at high voltages.
UKD2 series contactors are rated for up to 1500V DC depending on the specific model and pole configuration.
Yes, non-polarized models support current flow and interruption in both directions, essential for battery storage applications.
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