I bought a 30" cooktop and installed it in an existing location. It replaced a unit that was probably 40 years old. The old unit had four wires: red, black, white and bare copper. The junction box has two black and one white coming into it. The white wire continues out the top of the box. From the old unit the white and the copper were joined (together) to the white in the junction box and red went to one black and the black went to the other black.
The new unit has red, black and green only(no white or bare copper). I connected red and black to the same black wires as the original installation and the green to the white. This is a dedicated circuit with its own double breaker. The unit works and breaker didn't trip so I'm just checking with you to be safe..