The flywheel armature temperature must be at least 30 °C (86 °F) before start of rotation. If the flywheel temperature is below 30 °C (86 °F), a flywheel preheat cycle will be automatically initiated:
- Each time the keyswitch on the Flywheel Cabinet is turned to the "On-line" position and the flywheel temperature is below 30 °C (86 °F)
- Prior to Rotor Position Sensor (RPS) calibration and the flywheel temperature is below 30 °C (86 °F)
If the temperature is greater than 30 °C (86 °F), a preheat cycle will not normally be performed.
In a normal preheat cycle, the armature temperature determines the length of the preheat cycle. If the temperature is below 30 °C (86 °F), the system will calculate a required preheat cycle time from 6 minutes (min.) to 42 minutes (max.) The preheat is accomplished by sending 3-phase AC voltage to the armature at 85 amps.
After the preheat cycle, a thermal equalization time period is also determined. This period of time is used to allow the heat generated in the armature to be radiated into the rotor and allow temperatures to equalize. The minimum and maximum equalization times are 6 minutes and 15 minutes, respectively. The equalize time will be equal to the pre-heat time, but will not exceed 15 minutes.
Once the preheat/equalization cycle is complete, the UPS will automatically continue with start-up or RPS calibration.
If power to the Flywheel Cabinets has been off for over 48 hours, a 42 minute preheat cycle for the flywheels will be initiated. In most cases this preheat length will not be needed and will overheat the armature if completed. This overheating will result in a delay in obtaining nominal rotor speed. Call Caterpillar tech support to get a 42-minute preheat bypass password.
The Caterpillar representative will ask three questions to determine if the preheat time can be shortened. These questions are listed below, be prepared to answer these questions when calling.
- What is the temperature in the room where the flywheel is installed?
- How long has the flywheel been installed in this temperature environment?
- How long has it been since the flywheel was energized (full speed)?
If certain conditions exist, Caterpillar will issue a special password to over-ride the timing for preheat. In order to issue this command into the UPS you must have a computer connected via direct (serial) connection to the service port in the Flywheel Cabinet. Press the following keys simultaneously: "Ctrl", "Shift" and "6".
There is one password needed per Flywheel Cabinet.