Specifications

Document No. DER01120 DESCRIPTION AND OPERATION
Page 8 of 9 Effective Date 25 May 07
ELECTRICAL CONTROL SYSTEM OPERATION
The following paragraphs describe operation of the electrical control system. This information is
provided as an aid to understanding the centrifuge operation, which will facilitate operating the
equipment as well as for troubleshooting. The following paragraphs describe operation of the
drive motor and feed pump control circuits.
50 HP Drive Motor
With electric power supplied to the centrifuge (refer to Drawing 10147-00 in Section 11), pressing
the CENTRIFUGE ON button applies power through the switch’s normally open (N/O) contacts,
normally closed (N/C) thermal overload contacts, N/C over-torque switch contacts, N/C vibration
switch contacts, and N/C motor over-temperature contacts, energizing centrifuge run relay CR1.
With run relay CR1 energized, power is applied to the 50 HP electric drive motor. In addition, the
feed pump circuit is enabled, permitting startup of the slurry feed pump, and the elapsed time
meter is energized to begin recording operating time.
Feed Pump
Pressing the PUMP ON button applies power through the switch’s N/O contacts and normally
closed (N/C) thermal overload contacts, energizing pump start relay CR2. After the button is
released, power is maintained to CR1 through the button’s NC contacts, and the parallel circuit
formed by the N/O contacts of relays CR1 and CR2. Pressing the PUMP OFF button de-
energizes relay CR2, shutting down the feed pump motor and centrifuge drive motor.
Safety
The centrifuge control system protects the centrifuge in case of any of the following conditions:
• Excessive drive motor current demand
• Excessively high conveyor torque
• Excessive vibration
• Drive motor over-temperature
Any of these conditions de-energizes relay CR1, causing its N/O contacts to open, which de-
energizes centrifuge run relay CR1, shutting down the 50 HP electric motor and feed pump motor,
disabling the centrifuge. Once shut down by any of these conditions, the centrifuge cannot be re-
started until the anomaly is removed, and the CENTRIFUGE ON button is pressed.
Thermal Overload
If the drive motor or pump feed motor thermal overload trips due to excessive current flow, the
thermal overloads should be re-set and the centrifuge re-started only after removing the cause of
the overload. Pressing the centrifuge and pump starter RESET buttons mechanically close the
thermal overloads.