What's a good electric razor to use on a cat?

My cat is old for a cat and is starting to get matted fur (dreadlocks), which if left unchecked could cause harm to her.

I’ve been cutting them off one by one, but i need an electric razor to get further down to the root without hurting her.

What’s a good electric razor to use on cat’s fur? (Her fur is thick, almost like sheep’s wool).