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Siemens 3VA9978-0BB27 — Circuit Breaker Accessories

Siemens 3VA9978-0BB27 SENTRON undervoltage release, 440-480

MPN3VA9978-0BB27
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Siemens SENTRON 3VA9978-0BB27 undervoltage release, 440-480 V AC 50/60 Hz, 2.5 VA, 3 slots, Overvoltage Category III, pollution degree 3, for 3VA4/5/6 breakers.

Siemens 3VA9978-0BB27 datasheet (PDF)
StockContact for availability
Lead timeIn Stock wk
MOQ1 pcs
Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Jul 2026
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Specifications

Identification

3VA9978-0BB27 — Identification
ParameterValue
Product designationAccessories
AccessoriesAuxiliary release

Mechanical

3VA9978-0BB27 — Mechanical
ParameterValue
Width25.7 mm
Height65.1 mm
Depth28.8 mm

Other specifications

3VA9978-0BB27 — Other specifications
ParameterValue
Number of slots3
Stripped length10 mm
Degree of pollution3
Overvoltage categoryIII
Stripped length [In]0.4 in
Design of the productAuxiliary release
Surge voltage resistance4 kV
Apparent power consumption (Maximum)2.5 VA
Type of electrical connection (For auxiliary circuit)AWG18 / 750 mm

Product details

The Siemens SENTRON 3VA9978-0BB27 is an undervoltage release accessory for 3VA4, 3VA5, and 3VA6 molded-case circuit breakers. Rated for 440-480 V AC at 50/60 Hz, it draws a maximum apparent power of 2.5 VA. The surge voltage resistance is 4 kV, and it's rated for Overvoltage Category III with a pollution degree of 3 — meaning it's suited for fixed-installation panels in industrial environments where transient overvoltages and conductive dust or moisture are present.

Wiring to the auxiliary circuit uses AWG 18 (0.75 mm²) conductors with a stripped length of 10 mm (0.4 in). The connection type is screw-type, standard for panel wiring.

Frequently asked questions

What is the 3VA9978-0BB27 used for?

It's an undervoltage release for Siemens SENTRON 3VA4, 3VA5, and 3VA6 molded-case circuit breakers. It trips the breaker when the supply voltage falls below the rated range, preventing undervoltage damage or unsafe automatic restart.

What are the key ratings of 3VA9978-0BB27?

Rated voltage 440-480 V AC 50/60 Hz, maximum apparent power 2.5 VA, surge voltage resistance 4 kV, Overvoltage Category III, pollution degree 3. Dimensions: 28.8 mm deep, 25.7 mm wide, 65.1 mm high. Three slots required on the breaker.

MPN
3VA9978-0BB27