This post explains for the MOSFET.
The Part Number is K3451, 2SK3451.
The function of this transistor is 600V, 13A, N-Channel MOSFET.
The package is TO-220 Type
Manufacturer: Fuji Electric
Preview images :
Pinout: 1. Gate 2. Drain 3. Source
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Features :
1. High speed switching
2. Low on-resistance
3. No secondary breadown
4. Low driving power
5. Avalanche-proof
Maximum ratings :
1. Drain-source voltage : VDS = 600 V
2. Continuous drain current : ID = ±13 A
3. Pulsed drain current : ID(puls] = ±52 A
4. Gate-source voltage : VGS = ±30 V
5. Repetitive or non-repetitive : IAR *2 = 13 A
6. Maximum Avalanche Energy : EAS *1 = 216.7 mJ
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Applications:
1. Switching regulators
2. UPS (Uninterruptible Power Supply)
3. DC-DC converters