The functions of the diesel generator controller  are to provide: control, protection and indication.  They are designed to provide the state of the generator at all times and the ability to change that state. Equipment required in the control system include:

  • Measuring instruments (meters)
  • Status indicators
  • Protection relays
  • Warning/Alarm
  • Engine and alternator regulation
  • Command signalling

Today most systems contain microprocessors allowing to provide complex features such as:

  • True RMS output
  • Component monitoring
  • Configurable inputs
  • Engine ECU interface
  • Remote communication

Controllers range from basic start/stop operation to being able to monitor and control remotely. It is important that the application requirements and operating staff qualifications are considered in determining the correct system. If not this can lead to having an underutilised system or a system that cannot meet the requirements of the application.


Typical metering outputs are:

  • Hour run
  • Engine Speed
  • Engine oil pressure
  • Engine coolant temperature
  • Voltage
  • Current
  • Frequency
  • Battery Voltage
  • Battery Current
  • Power
  • Energy

Control Functions

Start – Enabled only when:

  • Engine is not running
  • Emergency stop button is not engaged
  • No alarms are present

 Auto Start

  • Engage starter for a time period (crank time)
  • Dis-engage starter upon engine start (crank disconnect)
  • Dis-engage starter after a time period of engine not starting
  • Repeat start attempt after a defined rest time and no of attempts (crank rest)
  • Upon engine no start signal fail to start (fail start)

Protection delay

Period between the generator reaching up to speed and voltage condition and protection circuits arming.  This is to allow oil pressure to build and voltage and frequency to stabilize.

  • Load breaker switching

Period between the generator reaching up to speed and voltage condition and closing the breaker to accept load. 

Status Indicators

Control systems provide the current mode of the generator. Common indicators that are useful for operators are:

  • Start Delay
  • Return delay
  • Cooling run
  • Fuel off
  • Fuel on
  • Cranking or Starting
  • Crank rest or Start rest
  • Failure to start
  • Crank disconnect
  • Running up to speed
  • Up to speed and volts
  • Running
  • On load
  • Breaker fail to close
  • Engine at rest


The control system monitors several conditions in order to limit generator faults and damage to connected load. Warning alarms are non-critical conditions however failure to address may lead to generator failure to start and or damage. Shutdown alarms are critical conditions that will trip the main circuit breaker and cut supply to the fuel solenoid.  Conditions may have an alarm and or warning parameter.

Typical conditions monitored are:

  • Low engine oil pressure
  • High coolant temp (Warning, Alarm)
  • High oil temp
  • High alternator winding temp (Warning, Alarm)
  • High alternator bearing temp (Warning, Alarm)
  • Low coolant level
  • Low fuel level (Warning)
  • Under Voltage
  • Over Voltage
  • Under speed
  • Over speed
  • Under frequency
  • Over frequency
  • Over Current
  • Earth Fault
  • Reverse power


With the advancement of microprocessors incorporated in control systems it has become easier to communicate remotely.  SCADA suite software, web based and mobile apps are the various solutions used to link generator controller to remote device.

The use of remote communication provides numerous benefits:

  • Travel to site may be avoided
  • Sites can be left unmanned
  • System parameters can be monitored to develop trends and aid in early failure detection
  • All operation, maintenance and performance data can be stored on PC and retrieved when required.
  • Instant alerts
  • Fault finding


The diesel generator  controller is the brains of the generator. Consisting of electronics and microprocessor, it can provide various functions ranging from basic to complex. The application and end user requirements need to be assessed in order to select the appropriate controller.  Parameters, inputs and outputs can be configured to ensure customers specifications are met.  Highly sophisticated systems require specialist engineers to provide the desired outcome.


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