Abstract: A sensorless vector control system of an induction motor includes: a magnetic flux and speed controlling unit for receiving a predetermined command value and generating two phase voltages of DC component; a first reference frame converting unit for converting the two phase voltages of DC component into three phase voltages of AC component; an inverter for receiving the three phase voltages of AC component and driving an induction motor; a current detecting unit for receiving the three phase power of AC component flowing between the inverter and the induction motor, and detecting and outputting three phase currents of AC component; a second reference frame converting unit for receiving the three phase currents of AC component, and converting and outputting two phase currents of DC component; a magnetic flux and speed estimating unit for receiving the two phase voltage of DC component and the two phase currents of DC component, estimating a magnetic flux and speed required for a vector control; and a primary re

Abstract: A sensorless vector control system of an induction motor includes: a magnetic flux and speed controlling unit for receiving a predetermined command value and generating two phase voltages of DC component; a first reference frame converting unit for converting the two phase voltages of DC component into three phase voltages of AC component; an inverter for receiving the three phase voltages of AC component and driving an induction motor; a current detecting unit for receiving the three phase power of AC component flowing between the inverter and the induction motor, and detecting and outputting three phase currents of AC component; a second reference frame converting unit for receiving the three phase currents of AC component, and converting and outputting two phase currents of DC component; a magnetic flux and speed estimating unit for receiving the two phase voltage of DC component and the two phase currents of DC component, estimating a magnetic flux and speed required for a vector control; and a primary re

Abstract: A lead oxide preventing apparatus for an automatic soldering device does not generate lead oxides around an impeller shaft inside a lead chamber. Industrial waste in the form of heavy-metal-contaminated material is reduced by installing a ring member and by placing an oxidation preventing agent into the ring members, or by installing a beating therein so that the molten lead does not contact portions of the impeller shaft.

Abstract: A method for classifying electro-discharge machining wave patterns by using a delay circuit, and a method for preventing arcs by classifying the electro-discharge machining waves. The voltage or current waves which are generated during an electro-discharge machining operation are classified by using high and low reference levels. Then the signals are delayed, inverted and AND-logic-combined to obtain a monitoring signal. The voltage or current waves are sampled immediately before the off-state of the delayed and inverted pulse, thereby classifying each of the electro-discharge machining waves. Thus the voltage or current waves which are generated during an electro-discharge machining operation are classified. Then, by utilizing the result of the classification, and interrupting the EDM discharge power immediately and momentarily when a wave is classified as an arc wave, damage due to the occurrence of arcs is prevented.