Rated Voltage:
Usually: 400V (50Hz system) or 480V (60Hz system), corresponding to the line voltage. This is the most common low voltage level.
It may also be: 525V, 690V (low voltage upper limit for some specific industrial occasions).
Rated Frequency:
50Hz (China, Europe, etc.) or 60Hz (North America, some Asian countries, etc.).
Compensation Capacity (Kvar Rating):
This is the core parameter, which refers to the maximum reactive power compensation that the device can provide.
Single cabinet capacity range: Usually between 30kvar and 600kvar, depending on the number of circuits, capacitor unit size and cabinet size. Larger capacity can be achieved by connecting multiple cabinets in parallel.
Single-circuit capacity (Step Size): refers to the capacity of a single switching circuit (such as a group of capacitors + switching switches), common ones are 5kvar, 10kvar, 15kvar, 20kvar, 25kvar, 30kvar, etc. The smaller the step size, the higher the compensation accuracy.
Switching Type:
Contactor Switching: The most economical, suitable for occasions with stable loads and infrequent switching. The response time is slow (hundreds of milliseconds to seconds).
Thyristor Switching / Static Var Compensator - SVC: No contacts, fast response speed (milliseconds, usually <20ms), suitable for occasions with rapid load fluctuations, frequent switching, and avoidance of inrush shocks (such as welding machines, rolling mills, elevators, etc.). The cost is relatively high.
Hybrid Switching: Combining the advantages of contactors and thyristors (thyristors are turned on, contactors carry steady-state current), taking into account both response speed and cost.
Capacitor Type:
Self-healing Metallized Film Capacitors: Modern mainstream, with self-healing characteristics, safe and reliable, long life.
Dry or gas-filled: Usually dry (epoxy resin potting) or slightly positive pressure inert gas filling (such as N2), oil-free and environmentally friendly.
Ingress Protection (IP Rating):
The cabinet protection level is usually IP30, IP41, IP42 (proof of solid foreign objects larger than 1mm, anti-drip or tilt drip) or higher, depending on the installation environment (such as distribution room, workshop).
Control Strategy:
Power Factor Controller (PFC): The core brain. Based on the real-time measured power factor (Cosφ) or reactive power (Q), combined with the set target value (such as 0.95~1.0), the switching of each circuit is automatically controlled.
Control target: Usually set the target power factor.
Control strategy: Cycle switching, coded switching (prioritize switching of small capacity circuits), etc., to optimize compensation accuracy and equipment life.
Measurement parameters: Voltage, current, active power, reactive power, power factor, frequency, harmonic distortion rate (THDv, THDi - depends on the controller level), etc.
Overload and protection (Protections):
Overvoltage protection: When the system voltage exceeds the set threshold (such as 440V), the capacitor is delayed or prohibited from being put into operation.
Undervoltage protection: Cut off when the system voltage is too low.
Overcurrent protection: Trip when the circuit current increases abnormally (short circuit, capacitor failure).
Overtemperature protection: alarm or cut-off when the temperature in the cabinet or capacitor is too high.
Harmonic protection: alarm or limit input when the harmonic content is too high (which may cause capacitor overload).
Three-phase unbalance protection: prevent capacitor overload due to imbalance.
Discharge protection: ensure that the residual voltage of the capacitor can be reduced to below the safe voltage (such as 50V) within a specified time (such as 1 minute or 3 minutes) after power failure.
Reactance rate (Reactor Rate / Detuning Rate):
Refers to the percentage of the inductive reactance (XL) of the reactor connected in series in the capacitor circuit to the capacitive reactance (XC) of the capacitor: Reactance rate (%) = (XL / XC) * 100%.
Function: suppress the inrush current of the closing switch; more importantly, suppress the amplification of harmonics of a specific order.

Improve Power Factor Correction (PFC): The core function is to compensate for the reactive power consumed by inductive loads (such as motors and transformers), so that the power factor is close to 1 and the reactive current of the line and transformer is reduced.
Reduce Line Losses: The reactive current is reduced, which significantly reduces the I²R loss on the line and has a significant energy-saving effect.
Increase Supply Capacity: Reducing the capacity of transformers and lines occupied by reactive current is equivalent to releasing part of the capacity for transmitting more active power.
Improve Voltage Profile: Reducing the voltage drop caused by reactive current on the line impedance helps stabilize the voltage level at the load end.
Reduce Electricity Costs: Avoid the power dispatching fee fine charged by the power company due to low power factor (and may even receive rewards); at the same time, save the electricity bill caused by increased line losses.
Optional Harmonic Mitigation: By selecting the appropriate reactance rate (e.g. 7%), the capacitor can be prevented from amplifying specific harmonics (mainly the 5th order) and the harmonic environment can be passively improved. But please note that this is not active filtering (APF) and cannot eliminate the source of harmonics.
Intelligent Control: Modern controllers are powerful and have functions such as data measurement, recording, communication (RS485, Modbus, etc.), event recording, fault diagnosis, and remote monitoring.
Modular Design: Modular design is usually adopted, and capacitors, reactors, switching switches, protection components, etc. are integrated on pluggable circuit modules for easy installation, maintenance and expansion.
Safety & Reliability:
High-quality self-healing capacitors are used.
Complete protection system (overvoltage, undervoltage, overcurrent, overtemperature, harmonic protection, etc.).
Forced discharge device ensures safe operation.
Comply with relevant safety standards (such as IEC, GB/T 15576, etc.).