APPENDIX D (Continued)
(4)
Compatibility with multimotor applications.
(5)
Ability to ride through a 3 to 5 Hz
power loss.
(6)
Lower initial cost.
f) The following disadvantages, however, should also
be considered:
(1) Motor heating and insulation breakdown in some
applications due to high frequency switching of transistors.
(2)
Non-regenerative operation.
(3) Line-side power harmonics (depending on the
application and size of the drive).
D-1.04.2 CSI Design. In the CSI drive design, the incoming
power source is converted to DC voltage in an SCR converter
section, which regulates the incoming power and produces a
variable DC bus voltage. This voltage is regulated by the firing
of the SCR's as needed to maintain the proper volt/hertz ratio.
SCR's are also used in the inverter section to produce the
variabe frequency output to the motor. CSI drives are inherently
current regulating and require a large internal inductor to
operate, as well as a motor load.
a)
CSI's have the following advantages:
(1)
Reliability due to inherent current limiting
operation.
(2)
Regenerative power capability.
(3)
Simple circuitry.
b) The following are disadvantages which should be
considered in the use of CSI technology:
(1)
Large power harmonic generation back into the
power source.
(2)
Cogging below 6 Hz due to square wave output.
(3)
Use of large and costly inductor.
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