The JK700 permanent magnet synchronous motor frequency converter is a high performance vector frequency converter. Using the international leading speed sensorless vector control algorithm, the D/Q axis inductance, the back EMF constant and the rotor magnetic pole position can be accurately identified. JK700 has high starting torque, strong overload ability and high speed of stability. It can be widely used in the applications of permanent magnet synchronous motor driven by air compressor, kowtow, air conditioner, water pump, textile and so on.