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Capstone Microturbine C1000 Series User Manual

Capstone Microturbine C1000 Series
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Capstone Turbine Corporation • 16640 Stagg Street • Van Nuys • CA 91406 • USA
Installation Guide: Capstone C1000S/C800S/C600S with C1000 Series Controller
480064 Rev C (December 2018) Page 106 of 122
Capstone reserves the right to change or modify, without notice, the design, specifications, and/or contents of this document without
incurring any obligation either with respect to equipment previously sold or in the process of construction.
7.8.2. Mitigating Harmonics
Below is a list of recommendations to reduce harmonic levels. Always consult with Capstone
whenever high harmonic loads represent a significant percentage of the total site load.
When specifying a VFD, always select IGBT-based VFDs with Active Front End power
inputs. If IGBT-based VFDs are not possible, select 18- or 24-pulse VFDs. Many VFD
manufacturers offer accessories for their VFDs to reduce harmonics, including in-line
chokes. Always select the VFD and accessories that offer the lowest current harmonics
at the input of the VFD.
The use of a transformer with a Delta winding on the microturbine side will effectively
filter out the third harmonic. It is recommended to always specify a transformer with a
delta winding on the microturbine side for Stand Alone only applications. This is required
for any Stand Alone installation with highly non-linear loads and current THD >8%. The
isolation transformer reduces “triplen” harmonics, which are common with non-linear
loads.
1
If the current THD at the microturbine is still reading above 8%, it is
recommended to improve the “worst offender” loads contributing the most to the THD
problem. If the microturbines will operate in Dual Mode with high harmonic loads, a
transformer with a delta winding on the microturbine side of the transformer can still be
used in combination with a grounding transformer on the delta circuit.
For example, if there is a large VFD that seems to be increasing the THD current when it
is operating, installing an input line filter can reduce the harmonics. However, there are
limits to this approach, especially for the lowest cost equipment using 6-pulse rectifier
bridge inputs. No simple input filter can reduce the current THD of these devices to meet
<8%. In this case, some combination of input line filters, and site-general isolation
transformer, or possibly even a hardware upgrade to a 12- or 24-pulse rectifier bridge
input VFD may be required. If these actions are not enough, a final option would be
installation of a custom-designed electrical filter tuned to reduce the specific harmonics
profile present on the site.
Many manufacturers of UPSs and large battery chargers also offer different options to
reduce current harmonics. As with the VFDs, always select IGBT-based UPSs with
Active Front end. If IGBT-based UPSs are not available, select 18 or 24-pulse UPSs.
Also make sure to include all options provided by manufacturer, such as in line chokes,
to offer the lowest harmonic distortion in input current.
For processes requiring large heaters (>10 kW) always specify gas-fired heaters or use
heat recovery from the microturbine exhaust. Most large heaters are modulated with
SCRs (also known as thyristors). These devices not only introduce high levels of
harmonics, but also generate very frequent and large power cycles, which significantly
shorten the microturbine battery life in SA operation.
Voltage and current harmonics of the load may have an increasing effect on the microturbine
voltage and current harmonics due to their interaction with the output inverter of the microturbine.
This interaction between the microturbine and load/grid harmonics can increase the steady-state
level of voltage and current harmonics in the system.
1
Additionally, the transformer will improve voltage balance by cancelling zero sequence currents. It is
highly recommended to specify the voltage of the transformer on the microturbine side to 480 VAC. This
will allow operation with maximum available current for starting loads.

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Capstone Microturbine C1000 Series Specifications

General IconGeneral
BrandCapstone
ModelMicroturbine C1000 Series
CategoryController
LanguageEnglish