A non-gated NbN on Si wafer field emission arrays are studied. The I-V measurements and emission characteristics of edge-shaped cathodes in atmosphere low-voltage regime are considered. Mathematical and computer models are presented. The current density obtained from experiment was up to 384 Ampere per square centimeter in emission area 9 sq.mm. Low-voltage regime (20 V) for near (~ 1mkm) interelectrode distance in diode configuration is discussed.