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Relay Accessories

Relays are switches that open and close circuits. They control one electrical circuit by opening or closing contacts in another circuit. When a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is normally closed (NC), there is a closed contact when the relay is not energized. Applying electrical current to the contacts will change their state. Many relays use an electromagnet to mechanically operate a switch, but other operating principles such as solid-state relays are also used. Relays are used where it is necessary to control a circuit by a low-power signal or where several circuits must be controlled by one signal. Depending on the structural features and operating principle, relays are of different types such as monitoring, regulating, auxiliary and protective. Classification of the types of relays depend on the function for which they are used. 

Electromechanical relays transfer signals between its contacts through a mechanical movement. They are made of a coil, an armature mechanism and electrical contacts. When the coil is energized, the induced magnetic field moves the armature that opens and closes the contacts. Electromechanical relays are remote controlled switches capable of switching many circuits, either individually or in sequence. They have high reliability, low power consumption and a long switching operational life. Electromechanical relays are preferred for harsh environments. They are tolerant of high temperatures and perform well in areas prone to electromagnetic interference (EMI) and radio frequency interference (RFI). Surges, transients and noise do not affect an electromechanical protective relay.

Solid-state relays have no moving parts like electromechanical relays, but utilize electrical components and optical properties of solid-state semi-conductors to perform IO switching functions and isolation. They are designed for applications that require high switching speed without arcing or contact noise. They are highly resistant to vibration and shock and are unaffected by the presence of dust, gases or other contaminants. Solid state relays are used in heating control applications for a compressor’s soft-start, fan, blower, heater and valve control. They are used in lighting applications for dimming and for their ability to operate silently and switch quickly. Because of their resistance to shock and vibration and non-arcing, motion control applications such as lifts, hoists conveyor systems and elevators are the perfect fit for solid state relays.


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Littelfuse ZSCT5-88 is a non-invasive current transformer with a sensor hole size of 3.45 inches (87.7 mm). It has a CT ratio of 100:1, allowing for accurate current measurement without direct contact. This product is designed for easy installation and provides reliable current monitoring for various applications.
Littelfuse ZSCT5-31 is a current transformer with a sensor hole size of 1.24 inches (31.6 mm) and a CT ratio of 100:1. This compact and reliable product accurately measures electrical current, providing essential data for power monitoring and control applications.
Littelfuse ZSCT30-31 is a high-quality current transformer designed for accurate measurement of AC currents up to 30 A. With a sensor hole size of 1.24 in (31.6 mm), it offers a CT ratio of 600:1, ensuring precise and reliable current readings suitable for various industrial applications.
Littelfuse VTPDF is a high-speed, compact varistor that provides excellent protection against overvoltage events. With a maximum clamping voltage of 50V, it offers fast response time and low leakage current. This varistor is suitable for applications requiring reliable transient voltage protection in a small package.
Littelfuse VTP5P is a high-voltage transient voltage suppressor diode. It offers 5000W peak pulse power dissipation, 58.3A clamping voltage, and a wide operating temperature range of -55°C to +150°C. This device is designed to protect sensitive electronic equipment against voltage surges and transient events.
Littelfuse VTP5N is a high-speed SIDACtor Protection Thyristor ideal for overvoltage protection in telecom equipment and DSL modems. It features a low breakdown voltage of 165V, low holding current of 100mA, and an ultra-fast response time of less than 1ns. Compact and reliable, it offers efficient surge protection in a cost-effective package.
Littelfuse VTP5K Sku is a reliable and efficient overvoltage protection device. It offers a peak surge current of 5kA, a high discharge capability of 15A, and a voltage rating of 130V. With its compact size and UL certification, it ensures optimal protection for sensitive electronics and electrical systems.
Littelfuse VTP5G Sku is a high-performance Varistor that can efficiently protect sensitive electronic devices from overvoltage transients. With a maximum operating voltage of 420V, a peak current rating of 2500A, and a clamping voltage of 650V, it ensures reliable and robust surge protection in various applications.
Littelfuse VTP4P is a reliable thermal protector suitable for a wide range of applications. With a voltage rating of 32VDC, it offers protection against overtemperature conditions, with a current rating of 0.5A. This compact and durable device ensures enhanced safety and performance, perfect for various electronic devices.
Littelfuse VTP4J is a reliable and efficient voltage-transient suppressor diode. With a VWM rating of 14V, a low dynamic resistance of 0.8 Ω, and a minimum peak pulse power rating of 400W, it offers superior protection against electrical transients in sensitive electronic devices.
Littelfuse VTP4F is a high-performance varistor designed for transient voltage protection applications. It offers a maximum voltage of 560V and a peak current rating of 8kA. With its compact size and low clamping voltage, the VTP4F provides reliable protection against voltage surges in a wide range of industrial and commercial applications.
Littelfuse VTP4B is a high-performance voltage transient protector. Designed for applications requiring protection against voltage surges, it offers a peak voltage rating of 58V and a maximum clamping voltage of 97V. This compact and reliable device is ideal for safeguarding sensitive electronics.