Sine wave power inverter

[Mateus]

Hello everybody !

I have been working with an inverter prototype 500 VA 24Vdc / 120 Vac 60 Hz, H-Bridge single-phase, Mosfet Switches IRF8010 VDSS 100V - dV/dt 16 V/ns, 2 Mosfets in parallel per Switch. The system runs controlled by means of a PWM 3.72 kHz generated by a Microchip PIC 16C74. The DC voltage source (A standard rectifier, Diode bridge + Capacitor), is connected to the H-bridge inverter by means of a duplex 12 AWG 0.9 meters length cable. Probably due to this cable inductance, the DC voltage at the inverter bridge has some spikes with short duration and high amplitude. I have tried to reduce these spikes with 2 electrolytic capacitors 330 µF 160V in parallel (C4), located at the H-bridge DC voltage entry, and it seems to reduce the Spikes quantity, but not the spikes amplitude.

Questions:
1) I have not used Snubber Networks for these switches because it is supposed Mosfets do not required them. Am i wrong , are the Mosfets subject to High risk in this case with these spikes ?
2) The noise caused by these spikes also can affect the control system performance. Could you please give me any suggestion to eliminate or at least reduce these spikes ?

Attached you can find the H-Bridge circuit diagram, and the obtained signals for a resistive 100W load connected to the HV side of a Step Up transformer 13.6/120 V.

Thanks for your comments.