"Jon" wrote in message
I have a main power box outside with two 50-amp breakers and one 30-amp
breaker. A voltage test shows 120 volts passing through them. Three of my
six 20 amp breakers in the inside box are not receiving any voltage.
They did not trip, just out of the blue for no apparent reason stopped
getting any power through them. The other three are working normally.
What is going on?

Main electrical connections can come loose. Have the electric company
"retorque" your main wire connections. If they will not do it, call an
electrician.