System information

GRAVITAS SABRE SERIES
INSTALLATION &OPERATING MANUAL
Manual No. SABRE-4 Page 16 11/27/07 sabre-man
1.2.1.8 Fan control
1.2.1.8.1 Fan speed control
The speed of STS fans is decided by the output current and the NTC temperature, with the NTC temperature taking
priority. When the temperature of the NTC is above 80ºC, the fan will operate at maximum speed according to the
valid fan number, otherwise, the fan will operate according to the load current. The following tables show the
relationship between the fan speed and load current. In normal circumstances, where both fans are running, the speed
is based on definition -2 shown below. When one of the two fans is locked, the speed is based on definition -1.
If both fans are locked for more than 2 minutes the STS will transfer to Inverter bypass mode and the STS module will
shut down.
One fan---- definition-1
Load Temperature of NTC Speed level
Load < 25% Speed2
25%  Load < 50% Speed3
75% < Load  50% Speed4
Load > 75%
<80ഒ
Speed5
Any load
>=80ഒ
Speed6(full speed)
Two fans---- definition-2
Load Temperature of NTC Speed level
Any Load
<80ഒ Speed1(the lowest speed᧥
Any Load
>=80ഒ
Speed5
1.2.1.9 Over temperature protection
On-line Mode (Inverters Providing Power)
When the temperature is over 85ºC, the STS will power the load through the bypass relay, and SCR2 will be open. If
the temperature reaches 90ºC, the bypass relay will open, and the load will be disconnected until the STS is restarted.
The system will re-establish power through the inverter with SCR2 closed and the relay open, when the temperature is
under 65ºC and at least one fan is running. The STS will then return to normal mode.
Off-line Mode (Utility/Mains Providing Power)
When the temperature is over 85ºC, the STS will transfer to on-line mode if the Inverter is normal, then the over
temperature protection is the same as on-line mode.
If the temperature is less than 65ºC and at least one fan is running, the system will re-establish the power through the
inverter with SCR2 closed and the relay open and the system will return to off-line mode.
x Inverter bypass: 85ºC
x Inverter bypass back: 65ºC
x Temperature protection: 90ºC