Demand more clean power.
The CPX series of variable frequency drives uses advanced 18-pulse clean power technology that significantly reduces line harmonics at the drive input terminals—resulting in one of the purest sinusoidal waveforms available. They prevent upstream transformer overheating and overloading, enabling the application of generators and other high-impedance systems.
Harmonic mitigation techniques can help protect equipment from potential damage, reduce power generation to overcome losses, and eliminate utility fines. Learn more about harmonics.
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| Technology |
Eaton VFD type |
How it works |
Typical THD |
Advantages |
Disadvantages |
|---|---|---|---|---|---|
| Inductive reactors |
EGS |
Mitigates higher-order harmonics by providing high input impedance that limits high-frequency currents. | 33-38% |
Low-cost, simple application |
Low effectiveness Voltage drop concerns |
| 12-Pulse converters |
HCX |
Two parallel 6-pulse converters fed by parallel isolation transformer paths, phase shifted 30°, which mitigates 5th and 7th order harmonics. Input impedance mitigates higher-order harmonics as well. | 12-18% |
Simple to apply Extremely robust |
Not as effective as other methods Relative high cost compared to passive filter |
| Passive filters |
Provides high input impedance for higher-order harmonics and a shunt-tuned reactor and capacitor to mitigate 5th and 7th harmonics. | 6-8% |
Simple retrofit Low cost for performance Insensitive to voltage balance |
Challenges with generator design Power factor issues Less robust than 18-pulse |
|
| 18-Pulse converters |
CPX |
Three parallel 6-pulse converters fed by a single-phase shifting autotransformer, phase shifted 20° to cancel all harmonics below the 17th. Input impedance mitigates higher-order harmonics as well. | 3-6% |
Simple to apply Extremely robust |
Higher cost on small hp |
| Active Front End drives |
RGX |
IGBT-based front end pulls relatively linear power from the line and uses a L-C-L filter to mitigate the IGBT switching noise. | 3-5% |
Slightly higher efficiency Immune to voltage imbalance Regeneration capability |
High cost, not as robust as 18-pulse |
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