1. Pierce 1 sweet potato several times with a fork. Place on a microwave-safe plate; cover with damp paper towels. Microwave at HIGH 8 to 10 minutes or until tender. Let stand 5 minutes. Peel potato, and place in a medium bowl; mash with a fork. Peel remaining sweet potatoes, and grate, using the large holes of a box grater. Stir grated potatoes into mashed potato. Gently stir in eggs, next 3 ingredients, and 1/4 cup green onions just until combined.
2. Pour oil into a 12-inch cast-iron skillet, and heat over medium heat to 350°. Carefully drop mixture by tablespoonfuls, in batches, into hot oil, pressing lightly to flatten. Cook 5 to 6 minutes on each side or until golden brown. Drain on paper towels. Place drained sweet potato cakes on a wire rack over an aluminum foil-lined baking sheet. Keep warm in a 200° oven up to 30 minutes. Sprinkle with remaining 1/4 cup green onions just before serving. Serve with lime wedges.