A circuit and process for disconnecting the current from the operating gap of an electrolytic processing device in the event of a short circuit in which a signal is produced from the AC current in the transformer supplying power to the gap, such signal indicating the gap current, the maximum value of that signal is stored for successive time periods and the stored value for a preceding period compared with the present signal to operate a switch in the current supply to the gap when a short circuit condition is detected.
The apparatus relates to an excess-current monitoring device in a direct-current generator having a controlled rectifier, and is particularly useful for electro-chemical machining. A reference signal is generated by a signal generator in accordance with the voltage drive of the rectifier and the mean current supplied to the load. The reference signal is supplied to a comparator which supplies a current-switch-off-signal when the value of the reference signal as compared to the instantaneous load current indicates excess mean load current. This enables optimum machining.
A clock line over-protection circuit (28) carried on an interface card (16) for interfacing synchronous clock line (20), power line (22), DC common line (24) and data line (26) between a host computer (12) and a plurality of data link modules (14) with a plurality of associated controlled devices (18) including a series resistor (52) interconnected between a clock disable switch (52) and a clock signal generating amplifier (48) and a current sensor circuit (64, FIG. 3) connected across the series resistor (50) to produce a current sensor signal on an output (62). The current sensor signal is integrated by an over-current protection circuit (58, FIG. 4) to produce an over-current detection signal that varies with the difference in the clock line current magnitude during clock signal phases of opposite polarity. A clock switch control circuit (54) actuates the clock disable switch (52) to turn off and to protectively disconnect the clock line (20) and the data link modules (14) coupled therewith from the clock signal generating amplifier (48). A latch (170, FIG. 6) maintains the clock disable switch (52) in the protective off state until reset and a circuit (110, 126) provides hysteresis to the clock switch control circuit (54) to prevent resetting while the over-current condition persist.
An apparatus for machining metal substrates such as honeycomb seals is provided. The apparatus includes a spindle unit including a motor and shaft. The motor is used for rotating the spindle shaft about its longitudinal axis. The spindle shaft is connected to a power source which converts it and a tool head secured thereto to an electrode. The electrode is positioned in close proximity to a rotating workpiece such that an arc is formed between it and the workpiece. Power to the electrode is adjustable to control the rate of metal removal from the workpiece. Circuitry is used to cut off power to the spindle shaft when the current from the power source exceeds a certain amperage for an extended period of time (such as three seconds to prevent nuisance cut off). The circuitry also allows arcing between the electrode and the workpiece without cutting off power to the spindle shaft.
