MAGNETIC ENERGY RECOVERY SWITECH HAVING PROTECTIVE CIRCUIT
First Claim
1. A magnetic energy recovery switch having a protective circuit and interposed between an AC power supply and a load to protect, against an overvoltage or an overcurrent, a magnetic energy recovery switch with a variable reactance function for turning ON/OFF of the AC current and changing a phase thereof, the magnetic energy recovery switch comprising:
- a bridge circuit constructed from four reverse-conductive type semiconductor switches;
a capacitor connected between DC terminals of the bridge circuit, recovering and storing magnetic energy at cut off of a current; and
control means;
wherein the protective circuit comprises;
a voltage detection unit connected in parallel with the capacitor and detecting a voltage of the capacitor;
a discharge circuit connected in parallel with the capacitor and having a discharge resistor and a discharge switch connected in series; and
a current detection unit interposed between the AC power supply and the load and detecting a current flowing to the load;
wherein the control means;
controls a phase of a gate control signal such that each of the four reverse-conductive type semiconductor switches is controlled so as to be paired with diagonally opposed one, such that the diagonally opposed pair of reverse-conductive type semiconductor switches are simultaneously turned ON/OFF in synchronization with the voltage of the AC power supply;
controls the gate of the discharge switch so as to short-circuit the discharge switch to discharge the electric charge of the capacitor through the discharge resistor when an output of the voltage detection unit exceeds a predetermined value; and
controls to limit a current by making the duty ratio of the ON/OFF of the pulse of the control signals smaller than 0.5 when the output of the current detection unit exceeds a predetermined value.
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Accused Products
Abstract
In order to protect Magnetic Energy Recovery Switch (MERS) against an overvoltage and an overcurrent a voltage detection unit is provided for detecting the capacitor voltage of the MERS and control means is provided to control so as to turn ON the switch of the discharge circuit connected in parallel with the capacitor to make the capacitor discharge the electric charge thereof when the output of the voltage detection unit exceeds a predetermined value. Moreover, a current detection unit is interposed between the AC power supply and the load for detecting the current flowing to the load, and the current limiting is carried out by making the duty ratio of the ON/OFF of the pulse of the gate control signals of the MERS switches smaller than 0.5, when the output of the current detection unit exceeds a predetermined value.
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Citations
21 Claims
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1. A magnetic energy recovery switch having a protective circuit and interposed between an AC power supply and a load to protect, against an overvoltage or an overcurrent, a magnetic energy recovery switch with a variable reactance function for turning ON/OFF of the AC current and changing a phase thereof, the magnetic energy recovery switch comprising:
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a bridge circuit constructed from four reverse-conductive type semiconductor switches; a capacitor connected between DC terminals of the bridge circuit, recovering and storing magnetic energy at cut off of a current; and control means; wherein the protective circuit comprises; a voltage detection unit connected in parallel with the capacitor and detecting a voltage of the capacitor; a discharge circuit connected in parallel with the capacitor and having a discharge resistor and a discharge switch connected in series; and a current detection unit interposed between the AC power supply and the load and detecting a current flowing to the load; wherein the control means;
controls a phase of a gate control signal such that each of the four reverse-conductive type semiconductor switches is controlled so as to be paired with diagonally opposed one, such that the diagonally opposed pair of reverse-conductive type semiconductor switches are simultaneously turned ON/OFF in synchronization with the voltage of the AC power supply;
controls the gate of the discharge switch so as to short-circuit the discharge switch to discharge the electric charge of the capacitor through the discharge resistor when an output of the voltage detection unit exceeds a predetermined value; and
controls to limit a current by making the duty ratio of the ON/OFF of the pulse of the control signals smaller than 0.5 when the output of the current detection unit exceeds a predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, 21)
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- 7. (canceled)
Specification