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Anonymous users2024-02-071. The basic concepts of circuits: current, voltage, resistance, Ohm's law for part of the circuit, electrical work and electrical power. 2. Simple DC circuit:
Electromotive force, Ohm's law for closed circuits, battery packs, series-parallel connection of resistors, hybrid connection of resistors, basic principles of multimeters, measurement of resistance, calculation of potential at each point in a circuit. 3. DC complex circuits: Gilchhoff's law and its application, superposition principle, Thevenin's theorem, equivalent conversion of current source and voltage source, interchange of star and triangle circuits.
3. Capacitance: the basic concept of capacitors and capacitors, commonly used capacitors, the connection of capacitors, the charging and discharging of capacitors, the electric field energy in capacitors, and the transition process in resistive capacitor circuits. (RC circuit) 4, magnetic field and magnetic circuit:
Electromagnetic induction phenomenon, the direction of the induced current, the law of electromagnetic induction, the phenomenon of self-inductance, the eponymous end of the mutual inductance coil, the application of electromagnetic induction, the transition process between electric field energy and RL circuit. 5. The basic concept of sinusoidal alternating current: the generation of alternating current, the physical quantity of alternating current, and the representation method of alternating current.
6. Sinusoidal AC circuit: pure resistance, capacitance, inductance circuit, and its series and parallel circuits, series and parallel resonant circuits, AC power, and actual components in AC circuits. 7. Three-phase AC circuit:
The generation of three alternating currents, the connection between the three-phase power supply and the three-phase load, the power and safe power consumption of the three-phase circuit. 8. Transformer and AC motor: transformer structure, working principle, power and efficiency, commonly used transformer.
Rating and inspection of transformers. Three-phase asynchronous motor: structure, working principle, control.
Single-phase asynchronous motor. Wait.
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Anonymous users2024-02-06This is not something that can be explained in a few words, alternating current, tributary current, ......Recommend "Electrician Basics" edited by Zhou Shaomin, which has a deeper understanding and satisfaction for you
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Anonymous users2024-02-0501 The basic knowledge of electricians includes left, zero, and right fire; During the operation of the transformer, the current of each phase of the transformer should not exceed the rated current; After the transformer is put into operation, it should be overhauled regularly.
The basic knowledge of electricians includes left, zero, and right fire; During the operation of the transformer, the current of each phase of the transformer should not exceed the rated current; After the transformer is put into operation, it should be overhauled regularly; In the system powered by the same transformer, it is not suitable to mix protective grounding and protective zero; The rated voltage of the secondary coil of the voltage transformer is 100V; The secondary side of the voltage transformer shall not be short-circuited when working.
Electrician basic knowledge development:
Because a large short-circuit current will be generated in the event of a short circuit, the transformer may be burned out, so fuses are installed on the primary and secondary sides of the voltage transformer for protection.
One end of the secondary side of the voltage transformer must be grounded.
The secondary side of the current transformer is close to a short-circuit condition when it is operating.
The secondary side of the current transformer is never allowed to open when working.
One end of the secondary side of the current transformer must be grounded to prevent it.
When the insulation of the primary and secondary coils breaks down, the high voltage on the primary side enters the secondary side.
When the current transformer is connected, pay attention to it.
First, the polarity of the secondary coil, China's transformer adopts the marking method of reduced polarity.
When installing, it is necessary to pay attention to the correct and reliable wiring, and the secondary side is not allowed to connect the fuse or switch. Even if for some reason the instrument or other device on the secondary side is to be removed, the secondary side must be shorted before it is removed.
Low-voltage switches refer to isolating switches, circuit breakers, fuses, etc. below 1kV.
The load controlled by the low-voltage distribution device must be clearly divided, and it is strictly forbidden to control and confuse one switch.
The interlocking device of the low-voltage power distribution device and the self-provided generator equipment should operate reliably. It is strictly forbidden to run self-provided power generation equipment in parallel with the power grid without permission.
Insulating pads should be laid on the passages operated and maintained before and after the low-voltage power distribution devices, and it is strictly forbidden to stack other items on the passages.
When connecting to the equipment, connect the equipment first, and then connect the power supply.
When disassembling the device, disassemble the power supply first, and then disassemble the device.
When connecting the line, connect the zero line first, and then connect the live wire.
When dismantling the line: dismantle the fire line first, and then dismantle the zero line.
The low-voltage fuse cannot be used as overload protection for the motor.
The rated voltage of the fuse must be greater than or equal to the working voltage of the distribution line.
The rated current of the fuse must be greater than or equal to the rated current of the melt.
The breaking capacity of the fuse must be greater than the maximum short-circuit current that may occur in the distribution line.
The selection of the rated current of the melt must meet the normal working current of the line and the starting current of the motor.
For short-circuit protection of loads such as electric furnaces and lighting, the rated current of the melt is equal to or slightly greater than the rated current of the load.
For a single motor, the melt rating (motor rating.
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Anonymous users2024-02-04<> solution: Solve by phasor method, U (phasor) = 100 90°V.
Circuit impedance: Z=10 30°=10 (COS30°+JSIN30°)=5 3+J5( )R+JX=R+J(XL-XC).
So: r=5 3 , xl-xc=5 . And xl=8 , so: xc=xl-5=8-5=3( ).
Circuit current: i (phasor) = u (phasor) z = 100 90 ° 10 30 ° = 10 60 ° (a).
Therefore: uc (phasor) = i (phasor) (jxc) = 10 60° 3 -90° = 30 -30° (v), i.e., uc = 30v.
Similarly, we can find that ur (phasor) = i (phasor) r=10 60° 5 3=50 3 60°(v), i.e., ur=50 3v.
ul (phasor) = i (phasor) jxl = 10 60° 8 90° = 80 150 ° (v), i.e.: ul = 80v.
The phasor diagram is as follows:
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