Delta VFD300C43S-HS User Manual page 82

Chapter 7 Optional AccessoriesC2000-HS
DC reactor
A DC reactor can also improve the power factor, reduce input current, and reduce interference
generated from the motor drive. A DC reactor stabilizes the DC BUS voltage. Compared to an AC input
reactor, the advantages are smaller size, lower price, and lower voltage drop (lower power dissipation).
Following table is the THDi value of Delta motor drive matching AC/DC reactor:
Drive Spec.
Reactor Spec.
5th
7th
11th
13th
THDi
THDi may have some difference due to different installation conditions (like wires
Note
or motors) and environment.
AC Output reactor
When the wiring between the drive and the motor is too long, the GF (Ground Fault) and OC (Over
Current) protection may be triggered. The over-length motor cable generates extremely large stray
capacitance, enlarges three-phase common mode current and triggers the GF protection. In this case, the
wire-to-wire and wire-to-ground stray capacitance is enlarged, and creates a surge current that makes the
drive output large current. An AC output reactor between the drive and the motor can increase the
high-frequency resistance and suppress the common mode current that outputs from the stray
capacitance.
The power transistor is switched via PWM to control the output voltage and frequency for AC motor
drive. During the switch process, the impulse voltage (dv/dt) rises and drops rapidly, makes the inner
voltage of the motor distributes unequally, can causes deterioration of motor isolation, bearing current and
electromagnet interference. Especially when the AC motor drive is connected with the motor by a long
leading wire, the damping leads to high frequency resonator, and makes impedance matching poor to
enlarge the voltage reflection. This phenomenon generates twice-input voltage in motor side, which easily
makes motor voltage overshoot to damage insulation.
Models with built-in DC reactor
No AC/DC reactor
31.16%
23.18%
8.6%
7.9%
42.28%
3% input AC reactor
27.01%
9.54%
4.5%
0.22%
30.5%
7-10
5% input AC reactor
25.5%
8.75%
4.2%
0.17%
28.4%
Table 7-9