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 77 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.
As seen from the examples above, the total impedance will increase with the
number of transformers in series. The recommended practice is to install the
least amount of transformers between the MTs and the highest voltage
connection point. In the examples above, it would be recommended to remove
TX2 and change TX1 voltage ratio to 34.5 kV/480 V in example 1. In example 2,
TX1 would have a ratio of 34.5 kV/400 V.
7.4.4. Transformer Benefits for 480/400 V Operation in Grid Connect
For 400 V applications, using an operating voltage of 480 V on the microturbine side of the
transformer allows for full power output without de-rate at a power factor of +/- 0.9. This is due to
the current limit of each 200 kW module being limited to 300 A.
7.4.5. Transformers for Stand Alone
For any Stand Alone installation with highly non-linear loads, an isolation transformer is required.
In addition to reducing harmonics, there are two major benefits that are worth consideration. First,
the energy storage in the transformer windings reduces voltage drop during motor direct on-line
(DOL) starts. Second, for 400 V applications, using an operating voltage of 480 V on the
microturbine side of the transformer provides up to 20% higher kVA margin for starting large
electric loads.
For sites requiring an isolation transformer, the recommended configuration is as follows:
Delta connection on microturbine side.
Wye connection is recommended on load side. However, delta connection on load side
is also acceptable if required by installation.
480 V output setting on microturbine side. This may not be commercially available in all
countries.
Impedance between 4-8%. Lower impedance provides better overall voltage regulation,
but may require configuration of a soft start ramp on the microturbines for installations
with three or more microturbines, due to the larger inrush current to energize the
transformer. The voltage ramp and frequency ramp start features are discussed in the
CRMS Maintenance TR 410014.
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