Emerson Series 600T - Manual (Page 53)

System Overview
41
5.1.12 Flywheel Sensors
Speed
The speed detection system uses an infrared emitter and a sensor to detect the rotation of the shaft. A
hole drilled through the shaft allows light to pass and is detected on the opposite side by an infrared
detector. This signal is used to detect the rotor angle, the speed and any over speed condition. The
pulsed signal passes into the 6711 DSP to be converted into a speed signal. This is then passed to the
2812 DSP. The 2812 checks for over-speed and shuts down the power electronics if this occurs. If
either of the processors lock-up, the rotor will slow down, this guarantees that on over-speed cannot
occur.
Temperature
The stator and rotor temperature detectors are thermocouples and are both conditioned in a similar
way. The stator sensor is a Type J thermocouple potted into the stator windings. The rotor sensor is a
non-contact type sensor that detects the temperature of the rotor surface and gives an output in a
Type J thermocouple format.
Figure 42 Schematic for the speed and temperature sensors
DSP 6711
TIMER INPUT
DETERMINES
SPEED
DSP 2812
DETECTS
OVERSPEED
CONDITIONER
AND DIVIDE BY 2
AMPLIFIERS, CONDITIONERS,
LINEARIZERS AND COLD
JUNCTION COMPENSATION IN
ONE CHIP
STATOR
TEMPERATURE
SENSOR
J TYPE
THERMOCOUPLE
ROTOR
INFRARED
DETECTOR
SUPPLY
FROM
CIRCUIT
BOARD
NON- CONTACT
ROTOR
TEMPERATURE
SENSOR
J TYPE
THERMOCOUPLE
OUTPUT
STATOR
WINDINGS