65results about How to "High protection precision" patented technology

The invention relates to an earth fault current detection circuit and method. A current transformer outputs a current signal to be directly connected to a full-bridge rectifier circuit formed by diodes; CTA+ and CTA- are connected to a rectifier bridge formed by diodes D2, D3, D4 and D5; CTB+ and CTB- are connected to a rectifier bridge formed by diodes D6, D7, D8 and D9; CTC+ and CTC- are connected to a rectifier bridge formed by diode D10, D11, D12 and D13; and each diode are connected with an acquisition resistor in series, adopts a fixed-frequency sampling mode, waveforms of phases A, B and C are superposed through a software algorithm, and an earth fault current effective value is calculated by adoption of a well-known effective value method. The circuit provided by the invention is simple in principle, low in cost and high in protection precision, and is particularly suitable for electrical appliance protection switches with a relatively high requirement for space volume and relatively small rated power.

The invention discloses a method for implementing overload inverse-time protection of an alternating-current motor, which comprises the following steps of: acquiring a three-phase current signal of the motor, calculating the load rate beta at the moment, acquiring inverse-time protection operation time t0 at the moment according to a permissible overload time function t=f(beta) when the beta is greater than a set value, setting a sampling period time as delta t, and acquiring an inverse-time protection operation remaining time T=t0-mdeltat (m is sampling frequency); and if the beta is changed during overload, acquiring a new operation remaining time T=tn-(t'n+mndeltat)n=0,1,2,3,... according to a temperature rise function of the motor, wherein when the T is equal to 0, a peripheral circuit implements protection. The method can make corresponding adjustment according to the change of the overload current during overload to further improve the reliability and protection precision of motor overload protection, can provide protection operation remaining time data for a product monitoring system, and is favorable for operation of a user; and the design is more humanized.

The invention discloses a low-voltage switch and a control method and device. The low-voltage switch comprises a mutual inductor, at least two followers, a first processor and a second processor, wherein the mutual inductor outputs differential signals; the followers are connected with the mutual inductor to enhance the driving capability of the differential signals; the first processor is connected with the mutual inductor to meter a preset parameter of a target object; and the second processor is connected with the at least two followers to protect the target object according to the differential signals output by the two followers. The technical problem that the low-voltage signal can only be used for protective equipment in the prior art is solved.

The invention discloses an intelligent control and protection switch, which comprises a casing, a control main board and a relay bottom board. The casing includes connection terminals, indicator lights, digital tube displays and keys; the control main board includes an ARM 32-bit high-speed single-chip microcomputer, a power supply module , signal conditioning module, protection module, drive module, 2-way dry contact output, storage module, human-computer interaction module and communication module; the relay base plate includes a magnetic latching relay and a sampling circuit; the mechanical structure is replaced by an electronic structure, and the switch is closed at the same time The voltage synchronization technology is adopted when the switch is turned off, and the current synchronization technology is adopted when the switch is turned off, which completely eliminates the phenomenon of arcing, thus saving the arc extinguishing device, simplifying the switch structure, greatly reducing the complexity of the equipment, higher integration, and smaller volume. Small and compact, the cost is minimized; using integrated circuit, electronic PCB board technology, SMT automatic placement technology, moisture-proof, high temperature resistance, high reliability, compact space, simple structure.