The above is an advertisement, the following is the main article, the two are unrelated:
1. Stator and Rotor. 2. Inductance and Capacitance. 3. Alternating Current and Direct Current. 4. Encoding and Decoding. 5. Open Loop and Closed Loop. 6. Series and Parallel. 7. Serial Communication and Parallel Communication. 8. Electromagnetic Induction and Electrostatic Induction. 9. Normally Open and Normally Closed. 10. Self-locking and Interlocking. 11. Forward and Reverse Rotation. 12. AC Motors and DC Motors. 13. Single Board and Microcontroller. 14. Rectification and Inversion. 15. Half Wave and Full Wave. 16. Scalar and Vector. 17. Stepper Motor and Servo Motor. 18. Monostable and Multistable. 19. Pulse and Analog. 20. Digital Circuit and Analog Circuit. 21. Momentary and Self-locking. 22. Synchronous and Asynchronous. 23. Qualitative and Quantitative. 24. Real and Imaginary Numbers. 25. Directly Proportional and Inversely Proportional. 26. Carrier Wave and Modulated Wave. 27. Self-excitation and Mutual-excitation. 28. Self-inductance and Mutual-inductance. 29. Autotransformer and Mutual Coupling. 30. Identical and Equal. 31. Equivalent and Congruent. 32. AC Relay and DC Relay.
1. Stator and Rotor:
The stator and rotor are components of a motor. The stator, as the name suggests, is the fixed part, which secures the coil or permanent magnet frame, while the rotor is the moving part, mounted on a rotating shaft fixed at both ends by bearings, and the fixed frame is securely connected to the stator.
2. Inductance and Capacitance:
Inductance and capacitance are a pair of dual components. The voltage across an inductor and the current flowing through it are in a derivative relationship. The current flowing through a capacitor and the voltage across it are also in a derivative relationship. Algebraic relationships and derivatives are fundamentally different; the voltage across a resistor and the current flowing through it are in an algebraic relationship, thus a resistor can sense whether there is current flowing through it, while an inductor senses change or no change, and a capacitor senses whether the voltage across it is changing or not. Therefore, if there is current in the circuit, it indicates that the voltage across it is changing.
3. Alternating Current and Direct Current:
As the name suggests, alternating current flows alternately, while direct current flows in one direction continuously.
4. Encoding and Decoding:
The encoding process involves providing the elevator’s position signal in binary code form to the computer. Decoding is the process by which the computer outputs the information to the display in a human-readable format.
5. Open Loop and Closed Loop:
Open loop and closed loop are very important concepts in automatic control. Both open loop and closed loop are inseparable from the concept of feedback: no feedback means open loop, while feedback means closed loop. Elevators with encoders are mostly closed loop.
6. Series and Parallel:
If the same current flows through components, they are in series; if the same voltage is applied across them, they are in parallel. Series circuits divide voltage, while parallel circuits divide current.
7. Serial Communication and Parallel Communication:
These are two forms of computer communication. In elevators, the best way to distinguish them is: if each button and switch corresponds to a single wire to the control board, that is parallel communication. If each call box has only two power lines and two communication lines, that is serial communication.
8. Electromagnetic Induction and Electrostatic Induction:
Electromagnetic induction and electrostatic induction are essential concepts in elevator technology. A thorough understanding of Faraday’s law of electromagnetic induction can provide great insights into generators, transformers, motors, and counter-electromotive force. The core of induction is to achieve this through non-contact changing fields passing through circuits. This is also the theoretical basis for interference. Electrostatic induction is also a fundamental theory of electricity, with its theoretical foundation being Coulomb’s law and the structure of molecules and atoms. The positively charged nucleus and negatively charged electrons result in an object becoming negatively charged when it gains electrons and positively charged when it loses electrons. The phenomenon of charged objects causing changes in the distribution of electrons in nearby objects, leading to some parts being positively charged and others negatively charged, is electrostatic induction. Efforts should be made to eliminate the hazards brought by electrostatic induction in elevators. CMOS chips should be short-circuited during transport to avoid fatal damage from static electricity. Static wrist straps should be used on control cabinets to prevent static damage when removing computer boards. Call panels and control panels should preferably be made of metal to allow grounding and avoid static damage.
9. Normally Open and Normally Closed:
These belong to electromagnetic switches, where their closure or disconnection is controlled by whether the coil is energized. The contact that closes when the coil is energized is called a normally open contact, while the contact that opens when the coil is energized is called a normally closed contact. The invention of electromagnetic switches opened the door to electrical automation.
10. Self-locking and Interlocking:
This is a pair of concepts frequently used in automatic control. When the start switch is pressed, it energizes the relay coil, and when the start button is released, the design that allows the coil to remain energized through the normally open contact controlled by the coil is called self-locking. Self-locking is akin to a master leading a disciple, where our goal in learning is to develop a self-locking point to achieve our set goals. Interlocking uses its own normally closed point within the other’s circuit, achieving mutual restriction, often used in forward and reverse control circuits. However, in switch circuits, opening the door takes precedence.
11. Forward and Reverse Rotation:
A motor can only rotate in two states: either counterclockwise or clockwise. One is defined as forward rotation, and the other as reverse rotation. The forward and reverse rotation of a DC motor is achieved by swapping the voltage polarity applied to the armature. In controlling three-phase AC motors, swapping any two phases can achieve the reversal of rotation.
12. AC Motors and DC Motors:
In a DC motor, both the stator and rotor are powered, with the excitation coil and armature coil fields not interfering with each other, allowing for smooth variable control. The disadvantage is that it has carbon brushes, is expensive, and has a high failure rate, limiting its applicable scenarios. The DC motor was officially applied in elevators in 1889, marking the safety of elevators. The three-phase AC motor was invented shortly thereafter and was soon applied to elevators. The three-phase AC asynchronous induction motor has only the stator powered, while the rotor is made of cast aluminum. Its structure is simple, cost-effective, and widely applicable. The integration of motor technology with generator and transformer principles provides many insights into the field. The characteristic of internal power increase under load is akin to a person being tempered in adversity to reach greater heights.
13. Single Board and Microcontroller:
The early microprocessor product Z80 is a standalone CPU. To complete functions, it needs to be installed on a single printed board along with interface circuits and memory, hence it is called a single board computer. A microcontroller is a further evolution where the CPU, memory, and interface circuits are integrated into a single chip, making it more powerful.
14. Rectification and Inversion:
A rectifier circuit is also known as a forward circuit, which converts alternating current to direct current, while an inverter circuit converts direct current to alternating current.
15. Half Wave and Full Wave:
In an AC circuit, when a diode is connected in series, the current or voltage waveform across the load has had half of its wave removed, hence it is called half-wave rectification. When four diodes are connected in pairs, the AC input is connected to the ends, and the output is the rectified positive and negative terminals.
16. Scalar and Vector:
A scalar has only magnitude and no direction, or a quantity that does not require direction consideration. A vector requires both magnitude and direction.
17. Stepper Motor and Servo Motor:
A stepper motor receives pulse signals and moves one step per pulse; if no pulse is received, it does not move. A servo waits for a signal to move; otherwise, it remains idle.
18. Monostable and Multistable:
Monostable means having one stable state, while multistable means having multiple stable states. The call buttons in elevators are typically monostable buttons. An emergency stop switch is bistable, and a maintenance switch is multistable.
19. Pulse and Analog:
A pulse is a discontinuous signal, while an analog signal is a continuous signal without interruption.
20. Digital Circuit and Analog Circuit:
A digital circuit is also known as a switching circuit or logic circuit; an analog circuit processes analog signals.
21. Momentary and Self-locking:
Momentary means the switch activates when pressed but does not activate when released; the elevator’s maintenance operation is momentary. Self-locking means the start button is pressed to run, and it continues to run even after releasing.
22. Synchronous and Asynchronous:
Synchronous means the rotor’s rotational speed matches the speed of the rotating magnetic field, while asynchronous means the rotor’s speed differs from the synchronous speed. The rotor of a three-phase AC asynchronous induction motor must always maintain a speed different from the synchronous speed to sustain rotational power.
23. Qualitative and Quantitative:
Qualitative refers to direction, while quantitative refers to the exact angle of direction. Qualitative assessments generally do not require calculations, while quantitative assessments yield precise calculable results.
24. Real and Imaginary Numbers:
Real numbers encompass both rational and irrational numbers. Mathematically, real numbers are defined as those corresponding to points on the real number line. They can be intuitively viewed as finite or infinite decimals. Real numbers and imaginary numbers together form complex numbers. Real numbers can be used to measure continuous quantities. In theory, any real number can be represented as an infinite decimal, with the digits to the right of the decimal point forming an infinite sequence (which can be periodic or non-periodic). In practical applications, real numbers are often approximated as finite decimals (with n decimal places, where n is a positive integer). In computing, since computers can only store a limited number of decimal places, real numbers are often represented as floating-point numbers.
In mathematics, an imaginary number is defined as a number of the form a + b*i, where a and b are real numbers, and b ≠ 0, with i² = -1. The term imaginary number was coined by the famous mathematician Descartes in the 17th century, as it was believed at the time that these were numbers that did not exist. Later, it was discovered that the real part a of the imaginary number a + b*i corresponds to the horizontal axis on a plane, while the imaginary part b corresponds to the vertical axis. Thus, the imaginary number a + b*i can be associated with the point (a,b) in the plane.
Imaginary numbers can be added to real numbers to form complex numbers of the form a + bi, where a and b*i are referred to as the real part and imaginary part of the complex number, respectively. Some authors use the term pure imaginary number to refer to what is commonly known as imaginary numbers, which denote any complex number with a non-zero imaginary part.
25. Directly Proportional and Inversely Proportional:
To describe in words: two associated quantities where when one quantity changes, the other also changes, and if the ratio (or quotient) of the two corresponding numbers remains constant, these quantities are said to be directly proportional, and their relationship is called a direct proportional relationship, represented graphically as a straight line. The changing patterns of two associated quantities in a direct proportional relationship are: both increase or decrease simultaneously while maintaining the same ratio.
Inversely proportional quantities change in opposite directions; if the product of the two corresponding numbers remains constant, these quantities are said to be inversely proportional, and their relationship is called an inverse proportional relationship.
If we denote the two associated quantities as x and y, and their product as k, the inverse proportional relationship can be expressed as:
(constant)
26. Carrier Wave and Modulated Wave:
A carrier wave is like an airplane or train, while a modulated wave is like a person. The carrier wave has a higher frequency, while the modulated wave has a lower frequency. For instance, sound waves need to be modulated with a high-frequency carrier wave to be transmitted over radio, and at the receiving end, demodulation (or detection) is required. This is akin to a person needing to get off the airplane or train upon arrival. In frequency converters, the carrier wave is a high-frequency triangular wave, while the modulated wave is a sine wave.
27. Self-excitation and Mutual-excitation:
To distinguish between a motor’s self-excitation and mutual-excitation: if an external excitation source is required, it is mutual-excitation; if not, it is self-excitation.
28. Self-inductance and Mutual-inductance:
Self-inductance is defined as the phenomenon where a change in current within a conductor leads to a change in the surrounding magnetic field, resulting in induced electromotive force that opposes the original current change. This phenomenon is known as self-induction. Mutual-inductance is defined as the phenomenon where a change in current in one coil induces electromotive force in a nearby coil. Mutual-inductance is a common electromagnetic induction phenomenon that can occur not only between two coils wound on the same core but also between any two circuits that are in close proximity.
29. Autotransformer and Mutual Coupling:
An autotransformer is defined as a transformer where the primary and secondary windings are on the same winding. It can be further categorized into adjustable and fixed. The term coupling refers to electromagnetic coupling; a regular transformer transmits energy through the electromagnetic coupling of primary and secondary windings, with no direct electrical connection between them. An autotransformer has a direct electrical connection between its primary and secondary sides, with its low-voltage winding being part of the high-voltage winding. Mutual coupling refers to the coupling of two separate components, such as a transformer with two coils (primary and secondary) coupled through a core. There is also capacitive coupling in electronic technology, which refers to connections made through other components.
30. Identical and Equal:
Identical and equal are not the same; for example, two resistors in series carry the same current, but it cannot be said that they are equal currents.
31. Equivalent and Congruent:
Equivalent means having the same effect, but the two things are not necessarily the same. For example, AC200 is equivalent to DC220; however, alternating current 220 and direct current 220 are not the same; they simply produce the same amount of heat when acting on the same resistance for the same duration.
32. AC Relay and DC Relay:
Firstly, their working principles are the same, as both rely on energizing the coil to generate a magnetic field that attracts the movable armature to switch on or off. The differences are: one operates on alternating current while the other on direct current; the coil of a DC contactor uses more wire than that of an AC contactor; and an AC contactor’s core has a short-circuit ring, while a DC contactor does not. The following explains their principles.
To understand their differences, it is essential to grasp the characteristics of alternating current and the properties of coils. In China, the mains electricity is 50Hz, meaning it changes 50 cycles per second, resulting in 100 moments of zero current. Coils have very low resistance; in a DC circuit, the winding behaves as a resistive element, meaning the voltage drop is determined by the coil’s resistance, independent of inductance. Therefore, the number of turns must be slightly more to increase the resistance value and prevent burning out the power supply.
In an AC circuit, the coil exhibits inductive characteristics, producing a voltage drop through inductance. At this point, the resistance value can be zero, so the number of turns does not need to be as high as that of a DC contactor, but the wire must be thicker.
The AC contactor’s core has a short-circuit ring because the alternating current through the coil has moments of zero current. When the current is zero, there is no magnetic field in the coil, causing the movable core to release. Before it can leave, current returns to the coil, causing it to be attracted again, resulting in repeated cycles of attraction and release. This can occur up to a hundred times per second, creating noise. To eliminate this noise, engineers devised a method of embedding a short-circuit ring equivalent to a closed coil in the core. When the contactor’s coil current approaches zero, an induced magnetic field is generated in the short-circuit ring, maintaining a continuous magnetic field in the core and thus eliminating noise.
In practice, if this short-circuit ring breaks, noise will occur, and in noise-sensitive areas, contactor replacements may be due to this reason, rather than contact point damage. Due to the reasons mentioned: DC contactors use more copper, are more expensive, and have lower noise; AC contactors are cheaper but may produce noise.
Author: Zhang Lixin, Harbin Great Elevator Co., Ltd. 13895710755
Harbin Great Elevator Co., Ltd. is continuously recruiting elevator maintenance trainees, with flexible learning schedules and guaranteed teaching until mastery is achieved. We offer external training courses for elevator technical school teachers, focusing on fundamental education while ensuring standards and safety.
Source WeChat Official Account: Great News
Recommended Articles:
(1) Amazing: No elevator with issues allowed to operate!
(2) Guangxi’s old buildings to receive a maximum subsidy of 180,000 yuan per elevator!
(3) Live: Modular elevator installation technology!
Long press this QR code to follow for free
For business cooperation, please call: 135-8595-9424