MOV Cross-Reference: Flyboat 34S and 22S vs Littelfuse, YAGEO and TDK

How to read these tables

The three-digit code is the varistor voltage, not the operating voltage (431 = 430V, 621 = 620V). MCOV is the maximum continuous operating voltage. Imax is the single-pulse peak surge current (8/20 µs). Energy figures carry their waveform: Flyboat figures are 2ms values from the factory manual; YAGEO and Littelfuse figures are 10/1000µs values. Figures measured with different waveforms are not directly comparable. A dash (—) means the value is not stated on this page.

Thermal protection: Flyboat MOVs are bare components. They do not contain an integrated thermal protection element and are not equivalent to thermally protected devices such as Littelfuse TMOV or TDK ThermoFuse. Where a thermally protected device appears below, it is a voltage-class reference only, not a drop-in equivalent.

34mm / 275VAC class: Flyboat 34SK431K

Item	Flyboat 34SK431K	Littelfuse V271HB34	Littelfuse TMOV34S271MP	YAGEO 431KS34
Package	34mm square	34mm square, 2 leads	34mm square, 3 leads incl. monitor pin	34S square, D(max) 38.0mm
MCOV AC / DC	275VAC / 350VDC	275VAC / 370VDC	275VAC / 369VDC	275VAC / 350VDC
Varistor voltage	430V	430V (387–473V)	430V (387–473V)	430V (387–473V)
Imax (8/20 µs)	—	40kA	40kA	40kA
Energy	910J (2ms)	400J (10/1000µs)	550J	600J (10/1000µs)
Thermal protection	None (bare MOV)	None (bare MOV)	Yes: integral thermal element + monitor pin	None (bare MOV)
UL	UL 1449 Recognized, File E335803	—	UL 1449, File E320116	UL, File E327997

Verdict: V271HB34 is the bare-MOV counterpart in the same size and voltage class (note the 20V higher DC MCOV on the Littelfuse part). 431KS34 matches on MCOV and varistor voltage. TMOV34S271MP shares only size and surge class; it is functionally not equivalent and must not be described as replaceable by a bare MOV.

385VAC / 620V class: Flyboat 34SK621K

Item	Flyboat 34SK621K	YAGEO 621KS34	TDK MT30K385M4 (ThermoFuse, reference)
Package	34mm square	34S square, T(max) 8.7mm	ThermoFuse module (thermally protected construction)
MCOV AC / DC	385VAC / 505VDC	385VAC / 505VDC	385VAC / 505VDC
Varistor voltage	620V	620V (558–682V)	620V
Imax (8/20 µs)	—	40kA	25kA
Energy	1,240J (2ms)	780J (10/1000µs)	600J (TDK stated value)
Thermal protection	None (bare MOV)	None (bare MOV)	Yes (thermal fuse)
UL	UL 1449 Recognized, File E335803	UL, File E327997	UL, File E231126

Verdict: 621KS34 is the same-ratings counterpart (620V, 385VAC/505VDC, UL 1449 Recognized) in the same 34mm square class; request footprint drawings to confirm the mounting interface. MT30K385M4 matches the voltage class only and is functionally not equivalent.

Other 34S voltage classes vs YAGEO KS34

Flyboat	MCOV AC / DC	Varistor voltage	Imax (8/20 µs)	Energy (2ms)	YAGEO counterpart	YAGEO MCOV AC / DC	YAGEO Imax	YAGEO energy (10/1000µs)
34SK271K	175VAC / 225VDC	270V	40kA	530J	271KS34	175VAC / 225VDC	40kA	420J
34SK511K	320VAC / 410VDC	510V	—	1,050J	511KS34	320VAC / 415VDC	40kA	700J
34SK751K	460VAC / 615VDC	750V	40kA	1,270J	751KS34	460VAC / 615VDC	40kA	850J

YAGEO varistor voltages match the Flyboat code in each row; all YAGEO parts above are UL File E327997. Note: 511KS34 DC MCOV is 5V higher than 34SK511K.

22SK431 vs Littelfuse V25S275P (same 275VAC / 430V class)

Item	Flyboat 22SK431	Littelfuse V25S275P
Package	22mm square	25mm disc
MCOV AC / DC	275VAC / 350VDC	275VAC / 350VDC
Varistor voltage	430V	430V (387–473V)
Imax (8/20 µs)	20kA	22kA
Energy	510J (2ms)	470J (10/1000µs)
Thermal protection	None (bare MOV)	None (bare MOV)
UL	UL 1449 Recognized, File E335803	—

Verdict: same voltage class; the Flyboat part is a 22mm square device with 2kA lower Imax. Note the Imax difference when comparing surge ratings.

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