by Steven Baker (bakersj) 05-20-2010 10:53 AM - edited 05-21-2010 09:38 AM
Non-linear loads create harmonics and voltage distortion, degrading the performance of a generator set. The percentage of voltage distortion is especially critical in data center applications. A generator set's alternator must be properly sized to limit voltage distortion to an acceptable level. Some types of non-linear loads are:
- Uninterruptible Power Supply (UPS)
- Battery Charger
- Variable Frequency Drive Motors – VFD (60 Hz)
- Variable Speed Drive Motors – VSD (50 Hz)
Filters & Pulse Rectifiers
To offset the unfavorable effects of non-linear loads, consulting engineers can upsize the alternator or recommend a higher rated (thus more costly) generator set.
However, adding filters and/or increasing the pulse count of pulse rectifiers (e.g. 6 pulse to 12 pulse, 18 pulse or 24 pulse) on a generator set can reduce the harmful effects of non-linear loads. Alternator life can be extended by avoiding the overheating caused by distortion. Power quality can be maintained or improved. Taking those measures can allow for a smaller ekW/kVA rated generator set and reduce the initial purchase cost.
- As a consulting/specifying engineer or a commissioning engineer, what are the applications or situations in which you recommend the use of filters or higher pulse rectifiers on a generator set?
- What types/size of filters and/or pulse rectifiers do you recommend to balance the cost-benefit trade-off between the purchase price of a filter or pulse rectifier, and the opportunity to downsize the required ekW/kVA rating of the generator set?
- What are some applications in which you have effectively reduced your customer's costs by using filters or pulse rectifiers?
- Are there any problems you have encountered using filters and/or pulse rectifiers?
- What are some rules of thumb you would advocate to a colleague who is faced with a customer site application where harmonics and voltage distortion are a concern?
Please post your answers and comments below.
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