Glossary

Technical terms and definitions related to D.C. contactors and switching

A

AC (Alternating Current): An electric current that periodically reverses direction, in contrast to direct current (DC) which flows only in one direction.
Ambient Temperature: The temperature of the surrounding environment in which equipment operates. Contactors have specified operating temperature ranges.
Arc: An electrical discharge that occurs when contacts open or close under load. Arc suppression is critical in contactor design.
Arc Suppression: Methods used to extinguish the electrical arc that forms when contacts separate, including magnetic blowout and arc chutes.
Auxiliary Contacts: Additional contacts used for signaling or control circuits, not intended for the main load current.

Breaking Capacity: The maximum current that a contactor can safely interrupt (break) without damage.
Busbar: A thick strip of copper or aluminium that conducts electricity within a switchboard, distribution board, or other electrical apparatus.

CCC: China Compulsory Certification - a mandatory safety mark for products sold in China.
Coil: The electromagnetic component that, when energized, creates the magnetic force to close or open the contactor contacts.
Coil Voltage: The voltage required to energize the contactor coil and operate the device.
Contact Bounce: The unwanted intermittent opening and closing of contacts during switching, which can cause arcing and wear.
Contact Gap: The distance between open contacts. A larger gap provides better electrical isolation.
Contact Resistance: The electrical resistance at the interface between closed contacts. Lower is better for efficiency.
Contactor: An electrically controlled switch used for switching a power circuit, similar to a relay but designed for higher current applications.
Continuous Current Rating: The maximum current a contactor can carry continuously without exceeding temperature limits.

DC (Direct Current): An electric current that flows in one direction only, as opposed to alternating current (AC).
Dielectric Strength: The maximum electric field that a material can withstand without breaking down (becoming conductive).
DPDT: Double Pole Double Throw - a switch configuration with two separate circuits, each with two possible output positions.
Duty Cycle: The ratio of time a device is operated compared to the total time, often expressed as a percentage.

Electrical Life: The number of operations a contactor can perform under specified electrical load conditions.
Emergency Disconnect: A manual switch designed for rapid disconnection of power in emergency situations.
Enclosure: A protective housing for electrical equipment, rated according to the level of protection provided (e.g., IP ratings).

Hermetically Sealed: Completely airtight, preventing the ingress of moisture and contaminants. Important for harsh environments.
High Voltage: In DC systems, typically refers to voltages above 60V, though definitions vary. Albright HV products handle up to 1000V DC.
Holding Current: The current required to keep a contactor coil energized after initial pickup.

Inductive Load: A load that causes current to lag behind voltage, such as motors and transformers. Requires special consideration for switching.
Inrush Current: The initial surge of current when a device is first energized, often several times higher than normal operating current.
IP Rating: Ingress Protection rating indicating the level of protection against solid objects and liquids (e.g., IP65, IP67).
ISO 9001: International standard for quality management systems, demonstrating consistent quality in products and services.
ISO 14001: International standard for environmental management systems, demonstrating commitment to environmental responsibility.

Magnetic Blowout: A method of arc suppression using a magnetic field to stretch and extinguish the arc when contacts separate.
Make Capacity: The maximum current that a contactor can safely close (make) without welding or damage to contacts.
Mechanical Life: The number of operations a contactor can perform without electrical load (no-load operations).
Motor Reversing: A switching configuration using two contactors to reverse the direction of a DC motor.

NO (Normally Open): Contacts that are open (not conducting) when the coil is not energized, and close when energized.
NC (Normally Closed): Contacts that are closed (conducting) when the coil is not energized, and open when energized.

Operating Temperature Range: The range of ambient temperatures within which a device will function correctly.
Overload: A condition where current exceeds the rated capacity of a device, potentially causing damage or failure.

Pick-up Voltage: The minimum coil voltage required to close the contactor contacts from the open position.
Polarized Contactor: A contactor designed for current flow in one direction only, often used in battery applications.
Pull-in Current: The current required to initially close the contacts of a contactor.

Relay: An electrically operated switch, typically for lower current applications than contactors.
Resistive Load: A load where current and voltage are in phase, such as heating elements. Generally easier to switch than inductive loads.
RoHS: Restriction of Hazardous Substances - EU directive limiting the use of specific hazardous materials in electrical equipment.

SPDT: Single Pole Double Throw - a switch with one input and two possible output connections.
SPST: Single Pole Single Throw - a simple on/off switch with one input and one output.
Stud Terminal: A threaded bolt connection point for high current cables, common in contactor designs.
Switching Frequency: The rate at which a contactor can operate (cycles per hour or minute).

UL: Underwriters Laboratories - a safety certification organization, UL listing indicates product safety compliance.

Voltage Drop: The reduction in voltage across a component, such as closed contacts. Lower is better for efficiency.

Welding (Contact): Unintended fusing of contacts due to excessive current or arcing, preventing normal operation.

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