Power Electronics

Varistors Comply with UL1449

Littelfuse, Inc. introduced TCMOV34S, SMOV34, and SMOV25 Series Varistor products designed to protect high energy circuits. The new TCMOV34S Series Varistor is a 34mm-square-format varistor that combines high maximum surge capability (40kA) with an integrated thermally active element. It is designed specifically to protect high energy circuits from the short circuit (SCCR) conditions and Abnormal Overvoltage Intermediate Current conditions specified in the 3rd edition of UL1449. In addition to suppressing voltage transients by clamping them to a safe level, the TCMOV34S Series Varistor is designed to disconnect itself from the circuit safely in the event of overheating due to abnormal over-voltage conditions. A built-in micro-switch can be used to indicate when the Varistor is disconnected from the circuit.

The TCMOV34S Series Varistor is designed to facilitate compliance with the 3rd edition of UL1449 for surge protection devices (SPDs). It offers a short circuit current rating of 200kA, as well as high peak surge current handling (up to 40kA) and high energy absorption capabilities. It can be wave soldered without the need for special or expensive assembly processes. It is also lead-free and RoHS-compliant.

The new Littelfuse SMOV25 and SMOV35 Series Varistor lines are 25mm-and 34mm-square MOV devices respectively. Each has a thermal disconnect designed to open in the event of overheating due to abnormal overvoltage as outlined in the 3rd edition of UL1449. The close proximity of the integrated thermal element to the MOV body ensures a quick thermal response. These devices have a separate micro-switch that can be used to indicate when the MOV is disconnected from the circuit. Both SMOV Varistor Series are designed to disconnect themselves safely from the circuit in a sustained over-voltage, limited current condition as outlined in the 3rd edition of UL1449. Their standard operating voltage range is compatible with common AC line voltage (115VAC to 750VAC).

Like the TCMOV34S Series, the SMOV25 and SMOV34 Series Varistor lines are designed to facilitate compliance with the 3rd edition of UL1449 for surge protection devices (SPDs). They offer high peak surge current handling and high energy absorption capabilities. They are also lead-free and RoHS-compliant.

Applications for all three Varistor lines include use in surge protection devices, AC panel protection modules, power transfer switches, AC/DC power distribution systems, photovoltaic systems, and cell phone base stations.

Littelfuse Inc.
Part Number: TCMOV34S

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