Many new energy vehicle manufacturing plants and charging stations encounter issues such as excessive power factor at night and inexplicable fines for over-compensation. Everyone knows that resolving capacitive overcompensation requires installing reactors to absorb excess capacitive reactive power.

However, the vast majority of electricians on site fell into the same trap: they directly used the 7% and 14% reactors that came with the capacitor bank. In the end, not only did this not solve the problem of fines, but it also caused the equipment to overheat, make abnormal noises, and even burn out.

Reactors that may look identical can have vastly different applications. Today, we'll delve into the methods for distinguishing reactors, their core differences, and selection criteria for reactive power compensation scenarios . After reading this, you'll never make the wrong choice again!

First, distinguish between the two types of reactors used on site, as their functions are completely incompatible.

In low-voltage power distribution rooms, common reactors are divided into two categories, which are not interchangeable and must never be used interchangeably:

Type 1: Harmonic suppression reactor (with % marking)

These are the 7% and 14% reactors most commonly found in capacitor banks. Their primary function is protection , not compensation.

be used in series with a capacitor . Its function is to suppress power grid harmonics, prevent harmonics from breaking down the capacitor, and filter circuit noise. It only provides protection and does not participate in reactive power regulation.

The second type: Reactive power compensation reactor (without percentage marking)

Specifically designed to address capacitive overcompensation and nighttime power factor advancement, it is positioned as a reactive power management device .

It can be used independently or in parallel with the grid . Its core function is to absorb the capacitive reactive power generated by the inverter and charging pile during nighttime standby, balance the reactive power of the grid, and solve the problem of penalties for exceeding the power factor standard.

II. Core Difference: Different pressure resistance values are the root cause of burnout due to mixing.

Many people wonder why reactors that look similar can be used in one case but burn out in another. The fundamental problem lies in their different voltage ratings.

Harmonic-type 7% and 14% reactors have extremely low withstand voltage and cannot withstand a full 400V operating condition. Their working principle is to divide the voltage in series with a capacitor, relying on the capacitor to share most of the voltage for normal operation.

Once connected to a 400V power grid alone, without capacitor voltage division, the reactor will instantly be in an overvoltage and overload state, rapidly heating up and saturating the iron core. Abnormal noises and overheating will occur within a short time, eventually leading to direct burnout, posing a great safety hazard.

The reactive power compensation reactor has a factory standard withstand voltage of 400V , which is perfectly compatible with low-voltage power distribution systems. It can operate independently on the grid for a long time, with stable withstand voltage and adaptable operating conditions, and is specially designed to deal with capacitive reactive power compensation scenarios at night.

III. Quick identification formula for instant differentiation on the spot

No complicated on-site testing is required. Just remember two simple identification methods for error-free product selection:

1. Check the nameplate parameters (most intuitive)

Nameplates indicating reactance rates of 7%, 14%, 12%, etc., are all harmonic protection models and should not be switched on or off separately . Nameplates without percentage markings, but marked with 400V withstand voltage and specifically for reactive power compensation, are for use in capacitive reactive power management.

2. Check the usage instructions

The reactor that is fixed in series with the capacitor is a harmonic protection reactor; the reactor that can be switched on and off independently and connected to the grid separately is a reactive power compensation reactor.

IV. Adapting to new compensation schemes: Selecting the right equipment is crucial for effectiveness.

Currently, new energy plants generally face the problem of large differences in reactive power between day and night: during the day, motor production is inductive and requires capacitor compensation; at night, photovoltaic and charging pile standby is capacitive and requires reactance absorption.

Hangzhou Shiyu Electronics' new generation controller supports bidirectional switching of capacitors and reactors , intelligently identifies the reactive power characteristics of the power grid, switches capacitors during the day to compensate for inductive reactive power, and switches reactors at night to absorb capacitive reactive power, fully automatically adapting to all operating conditions.

However, this solution requires the use of a 400V non-percentage compensation reactor . If a harmonic reactor is used incorrectly, even the most advanced controller will not function properly and may cause equipment failure.

V. Summary: Core Principles for Reactor Selection

1. Reactors with 7% or 14% reactance rate only provide harmonic protection and do not provide compensation; they are strictly prohibited from being connected to the grid independently.

2. Mixing series reactors will likely cause them to overheat and burn out, posing a significant electrical safety hazard;

3. For nighttime capacitive overcompensation, a dedicated reactive power reactor with a 400V withstand voltage and no percentage requirement must be used;

4. Only by using a bidirectional hybrid switching controller can the issues of day-night power factor fluctuations and power regulator penalties be completely resolved.