TDK Aims to Offer Surge Protection With Smaller Disk VaristorsNovember 18, 2019 by Gary Elinoff
The new varistors feature surge protection of 6kA along with multiple-pulse protection against lower-level threats.
TDK has announced the EPCOS Compact S14 AdvanceD-MP series of metal oxide disk varistors (MOVs). The new series affords the same protection as the EPCOS S14 AdvanceD-MP standard series but features smaller dimensions.
The disk diameters of the new devices range from 13mm to 14mm, for a reduction of about 3mm when compared to the old standard.
EPCOS Compact S14 AdvanceD-MP series. Image from TDK
The new units are also known as the B72214P2 series under TDK’s proprietary SIOV designation. Like the older series, the EPCOS Compact S14 AdvanceD-MP MOVs feature a maximum surge current capability of 6 kA at 8/20 µs, according to IEC 62368-1.
All members of the new compact series have UL, CSA, VDE and IEC approval, and they all operate over a voltage range from 130 VRMS to 460 VRMS. The units provide multiple-pulse protection against repetitive low-level current surges.
Their main applications will include switching power supplies, smart meters, home appliances, and LED lighting drivers.
All units can take a 6000 amp 8/20 μs pulse one time, and PMAX is 0.60 watts. And, as per UL 1449 (4th edition) and other TDK varistors, like the ThermoFuse varistors, the MOVs feature useful energy absorption metrics.
The new MOVs can absorb a 3000 amp 8/20 μs pulse 15 times. Note the different operating voltages and protection capacities, listed below, under both designations.
These specifications are for a maximum TA of 105 °C.
Exact height specifications can be found in the datasheet. While the width of all members of the series is between 13mm and 14mm, the variations in height are between 17mm and 18mm, and thickness varies between 4.7mm and 8.5mm.
Dimensional drawing for TDK’s EPCOS Compact S14 AdvanceD-MP series of MOVs (B72214P2). Image from TDK
In all cases:
- The “e” dimension is 7.5mm, ± 1mm.
- The “l” dimension is 20.0mm, minimum.
- The “d” dimension is 0.8mm, ±0.05mm.
The MOVs operate over a range of -40°C to +105°C as per IEC 61051.
Around the Industry
Because there are many trade-offs with MOVs, engineers would do well to give the manufacturers’ datasheets the careful consideration they deserve.
Littelfuse’s LA Varistor Series includes radial-lead MOVs designed to operate continuously across AC power lines. They have maximum VRMS specifications ranging from 130V to 1000V and energy absorption capabilities of up to 360J. They are available in 7mm, 10mm, 14mm, and 20mm sizes.
Members Bournes MOV-20DxxxK Series of 20mm radial-leaded MOVs include units with varistor voltages ranging from 18V to 1800V and VRMS voltages from 11V to 1100V.
What is your experience working with MOVs? Let us know in the comments below.