DC Reactors

DC reactors prices as listed on the website, ATO DC reactor for vfd, provide power of 2 hp, 5 hp, 10 hp, 20 hp, 30 hp, 40 hp to 200 hp DC reactor, output DC voltage 220V, 380V, 400V to 1200V for your choice, DC reactor material copper or aluminum can be. Other powers can be customized, please contact us.

What is a DC reactor ?

DC reactor is connected between the diode and the DC bus. Depending on the observed harmonic order, they may be slightly less or more effective in eliminating harmonics than AC reactor. DC link choke is typically smaller than AC line reactor, and they add the necessary impedance to reduce harmonics without reducing voltage. While a DC reactor does not add any additional buffering to the voltage surges seen by the rectifier, it does prevent current surges. The smaller size and lack of voltage drop provides some benefits over DC reactors while providing similar harmonic reduction.

Role of DC reactor

• Prevents inverter commutation failure.
• Reduces voltage and current harmonics in the DC line.
• Reduces ripple coefficient.
• Limiting the current in the rectifier in case of line short circuit.
• DC reactors are connected in series on each pole of the converter. Inductance is about 0.4 to 1.0H.

Note: The value of the inductance must be taken to ensure that no resonance occurs in the DC circuit at industrial frequency.
DC reactors can increase the power factor to more than 0.9. Because of its small size, many inverters have installed DC reactors directly in the inverter. In addition to improving the power factor, DC reactors also weaken the shock at the moment when the power is first turned on. If equipped with both AC reactor and DC reactor, the power factor of the inverter speed control system can be increased to more than 0.95.

Role of DC reactor on VFD

1. Reduce harmonics generated by inverter rectification.
   
   DC reactor can effectively suppress the harmonics generated during the rectification of the inverter and reduce the interference of the inverter rectification harmonics to    other sensitive power-using equipment.
   
   
2. Limiting the AC component.
   
   The DC reactor can limit the AC current superimposed on the rectified DC current of the inverter to a certain specified value.
   
   
3. Keeping rectified current continuous.
   
   The rectification current of a VFD is discontinuous after it is rectified by a rectifier device, but by adding a DC reactor, the rectification current can be continuous.
   
   
4. Reduce the current pulsation value.
   
   DC reactors can significantly reduce the pulsation of the current.
   
   
5. Improving the stability of the rectification link.
   
   DC reactors can significantly improve the stability of the rectifier link of the VFD.
   
   
6. Improving the power factor of the VFD
   
   DC reactor can significantly improve the power factor of the variable frequency inverter, which can generally be increased to ≥0.93.

How to choose DC reactor for VFD?

1. There are switched reactive power compensation capacitors or with thyristor phase control load
   
   For the occasion that there is a switching reactive power compensation capacitor screen on the same power node provided to the VFD working power, or with thyristor phase control load, DC reactor should be selected. This is mainly due to the instantaneous change of reactive power caused by the switching of the capacitor screen, which will cause sudden changes in the grid voltage, and the harmonics and grid waveform gap caused by the phase-controlled load, which may cause harm to the input rectifier circuit of the inverter.
   
   
2. Unbalanced three-phase power supply
   
   When the unbalance of the three-phase power supply to the inverter exceeds 3%, DC reactor should be used.
   
   
3. There is a power factor requirement
   
   If there are certain requirements for the power factor at the input of the inverter, which needs to be increased to above 0.93, DC reactor should be used.
   
   
4. Large-capacity transformer
   
   If the inverter is connected to a large-capacity transformer, and the current flowing through the input power circuit of the inverter may cause harm to the rectifier circuit of the inverter, a DC reactor should be used.

How to choose reactance of reactor?

1. Reactance is an important parameter of reactor, and the size of reactance will directly affect its function and the safety of the system. In order to select the reactance rate appropriately, it is necessary to understand the background of harmonics in the power grid where the capacitor is connected. Only after the actual measurement of each harmonic can the capacitor be matched with the reactor connected in series.
2. The background harmonics at the access of the compensation capacitor are mainly 3rd and 5th, and the content of both is larger, it is appropriate to choose 12% and 4.5% ~ 6% two kinds of reactance mixed way of series reactor, to ensure the suppression of the 3rd harmonic amplification as a premise. The advantages of this program than all use series 12% program can reduce reactive power loss.
3. When the background harmonics at the access of compensation capacitor are mainly 3rd and contain more than 5th harmonics, but the content is less, 0.1%~1% reactor can be used.
4. When the background harmonics at the access of compensation capacitor are mainly 3rd and 5th, but the content of 3rd harmonic is less, and the content of 5th harmonic is more or close to the standard value, 5%~6% reactor should be used.
5. When the background harmonics of the compensation capacitor access is 5 and above, and the 5th harmonic content is larger, should choose 6% series reactor.
6. When the compensation capacitor access to the grid contains a variety of harmonic components, and coarse content are larger, series single reactor reactance rate can be The following formula to determine.
   xL =axc/n2
   a: reliability coefficient (generally take a = 1.2 ~ 1.5)
   XC: Base-wave reactance of capacitor bank
   n: the minimum number of harmonics with large content
   At this time the capacitor branch for the larger content of each harmonic will not produce amplification.
7. Newly built power substation can not know the background wave of the grid, the compensation capacitor device can choose damped current limiter, the rated current of the series reactor in the current limiter can be selected according to the final capacity of the capacitor bank.