The circuit board of a frequency inverter mainly includes a power board, control board, drive board, and front panel.

I. Resistors Resistors are represented by the letter R on the circuit board. Units include ohms (Ω), kiloohms (KΩ), and megaohms (MΩ). Resistor symbols are represented as follows: 1. By resistance value: fixed resistors, adjustable resistors, special resistors. 2. By material: carbon film resistors, metal film resistors, wire-wound resistors, non-inductive resistors, thin-film resistors, etc. 3. By mounting method: through-hole resistors, surface-mount resistors. 4. By function: load resistors, sampling resistors, shunt resistors, protection resistors, etc.

II. Capacitors Capacitors are components capable of storing electrical energy, mainly used for filtering, coupling, and resonance. Our frequency inverter circuit boards also utilize these functions, so capacitors are indispensable.

III. Inductors Inductors (inductor coils) and transformers are electromagnetic induction elements made of insulated wires (such as enameled wire, cotton-covered wire, etc.). According to their application, inductors can be classified as oscillating inductors, correction inductors, cathode ray tube deflection inductors, choke inductors, filter inductors, isolation inductors, and compensation inductors.

IV. Diode: A diode is a power electronic component with switching capability. It combines P-type and N-type semiconductors and conducts when a forward voltage is applied.

V. Transistor: A transistor, also known as a bipolar junction transistor (BJT), is a semiconductor device that controls current. Its function is to amplify weak signals into larger electrical signals; it is also used as a contactless switch. 1) By material: Silicon transistors, Germanium transistors

2) By structure: NPN, PNP

3) By function: Switching transistors, power transistors, Darlington transistors, phototransistors, etc.

4) By power: Low-power transistors, medium-power transistors, high-power transistors

5) By operating frequency: Low-frequency transistors, high-frequency transistors, overclocking transistors

6) By structure and manufacturing process: Alloy transistors, planar transistors

7) By mounting method: Through-hole transistors, surface-mount transistors

VI. IGBT IGBT (Insulated Gate Bipolar Transistor) is a composite, fully controllable, voltage-driven power semiconductor device composed of a BJT (Bipolar Junction Transistor) and a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor).

VII. Optocoupler It is a device that transmits electrical signals through light. It typically encapsulates the light source (light-emitting diode) and the light-receiving unit (photosensitive semiconductor tube) in the same package. When the light emitter emits light, the light receiving unit receives the light and generates a photocurrent, which flows out from the output terminal, thus realizing the "electricity-optical-electricity" conversion.

VIII. Crystal Oscillator: A crystal oscillator, generally called a crystal resonator, is an electromechanical device made of a quartz crystal with very low electrical loss, precisely cut, ground, plated with electrodes, and soldered with leads.

IX. Other Components: Multi-pin chips, digital tubes, liquid crystal displays, relays, buzzers, etc.