York YK Style H Operation Manual page 179

VSD – High Phase B Instantaneous Current
See the previous VSD – High Phase A Instantaneous Current message.
VSD – High Phase C Instantaneous Current
See the previous VSD – High Phase A Instantaneous Current message.
VSD – Phase A Gate Driver
A second level of current protection exists on the VSD driver boards themselves. The collector-to-
emitter saturation voltage of each IGBT is checked continuously while the device is gated on. If
the voltage across the IGBT is greater than a set threshold, the IGBT is gated off and a shutdown
pulse is sent to the VSD Logic Board shutting down the entire VSD system. A gate driver fault can be
initiated when the VSD is not running.
VSD – Phase B Gate Driver
See the previous VSD – Phase A Gate Driver message.
VSD – Phase C Gate Driver
See the previous VSD – Phase A Gate Driver message.
VSD – Single Phase Input Power
This shutdown is generated by the SCR trigger control and relayed to the VSD Logic Board to
initiate a system shutdown. The SCR Trigger control uses circuitry to detect the loss of any one of
the three input phases. The Trigger will detect the loss of a phase within one half line cycle of the
phase loss. This message is also displayed every time power to the VSD is removed or if the input
power dips to a very low level.
VSD – High DC Bus Voltage
The VSD's DC Link Voltage is continuously monitored and if the level exceeds 745 VDC, a Bus Over-
Voltage shutdown is initiated. If this shutdown occurs, it will be necessary to look at the level of the
460 VAC applied to the drive. The specified voltage range is 414 to 508 VAC. If the incoming voltage
is in excess of 508 VAC, steps should be taken to reduce the voltage to within the specified limits.
VSD – Logic Board Power Supply
This shutdown is generated by the VSD Logic Board and it indicates that the low voltage power
supplies for the Logic Boards have dropped below their allowable operating limits. The power
supplies for the Logic Boards are derived from the secondary of the 120 to 24 VAC transformer,
which in turn, is derived from the 480 to 120 VAC control power transformer. This message usually
means the power to the VSD has been removed.
VSD – Low DC Bus Voltage
If the DC link drops below 500 VDC (or 414 VDC for 50 Hz applications), the drive will initiate a
system shutdown. A common cause for this shutdown is a severe sag in the incoming power to the
drive. Monitor the incoming three-phase AC line for severe sags and also monitor the DC link with a
voltmeter.
VSD – Low DC Bus Voltage
(575V/60 Hz applications)
If the DC Link Voltage falls below 600 VDC while running, this shutdown is performed.
VSD – DC Bus Voltage Imbalance
The DC link is filtered by many large electrolytic capacitors, rated for 450 VDC. These capacitors
are wired in series to achieve 900 VDC capability for the DC link. It is important that the voltage be
shared equally from the junction of the center, or series capacitor connection, to the negative bus
and the positive bus. This center point should be approximately ½ of the total DC Link Voltage. Most
Model YK Style H Centrifugal Liquid Chillers with OptiView Control Center 179