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Orion Marine
Marine Electrical

Marine Generators, Motors & Drives

Generators that will not share load. A motor that trips its starter on every second start. A drive whose maker stopped supplying spares years ago. We work on the electrical side of the machines that generate and use the vessel's power: protection, excitation, control, connections and drives.

Power path

Symptoms and checks along the power path

The symptom and its cause can sit at different points between the generator and the load. These are the checks we make at each stage.

  1. 01Generation

    Generators in parallel

    Sets running in parallel share active power through their governors and reactive power through their AVRs. When sharing is unstable, we separate governor, AVR and signal problems from faults in the alternator before deciding where the cause sits.

    What the vessel sees: kW sharing drifts apart as the load changes
    Where we look: Governor droop settings and speed signals, the load-sharing lines, the kW transducers
    What the vessel sees: kVAr sharing is unstable, or one set runs hot
    Where we look: AVR droop and settings, the current transformer and its polarity, voltage sensing
    What the vessel sees: A set trips on reverse power
    Where we look: Governor response during load changes, the relay setting and its time delay, the power measurement
    What the vessel sees: A set will not synchronise, or closes with a bump
    Where we look: The synchroniser, voltage and frequency matching, breaker closing time
    What the vessel sees: A set drops out when a large motor starts
    Where we look: Voltage dip and AVR response, the running reserve, how the motor is started

  2. 02Distribution

    Between the board and the machine

    A machine problem can turn out to be a supply problem. We check voltage at the motor terminals, the feeder condition and the breaker's settings before blaming the machine. Work on the boards themselves is covered under switchboards and power distribution.

    What the vessel sees: Motor slow to start, starter contacts burning
    Where we look: Voltage at the terminals during starting, cable size and length, the connections
    What the vessel sees: Breaker trips on starting although the motor is healthy
    Where we look: Trip settings against the starting current, and the starting method

  3. 03Starter or drive

    Starters and variable frequency drives

    The starter or drive sits between the supply and the motor and takes commands from the control system. A fault at this stage can come from the supply, the starter or drive itself, the motor, or the control interface.

    What the vessel sees: Drive trips on overcurrent or earth fault
    Where we look: Motor cable insulation, the motor itself, the acceleration settings
    What the vessel sees: Drive trips on DC-bus overvoltage as the load slows
    Where we look: Deceleration ramp, the braking arrangement, supply voltage
    What the vessel sees: Drive faults after a blackout
    Where we look: Parameters lost or returned to default, restart settings, the control supply
    What the vessel sees: Star-delta starter trips at changeover
    Where we look: Changeover timing, the contactors, the overload setting
    What the vessel sees: Drive runs locally but not from remote
    Where we look: The control signals and the interface, which is automation and control work

  4. 04Motor

    Electric motors

    Our work on motors is electrical: the supply, the connection, the protection and the condition of the insulation. Where a motor needs a workshop rewind or a mechanical overhaul, we say so.

    What the vessel sees: Motor runs hot at normal load
    Where we look: Phase currents and their balance, supply voltage, cooling, the overload setting
    What the vessel sees: Insulation alarm whenever the motor runs
    Where we look: Insulation resistance of the winding and of the cable, moisture in the terminal box
    What the vessel sees: Motor turns the wrong way after work on it
    Where we look: Phase sequence at the terminals, corrected and marked
    What the vessel sees: Replacement motor larger than the old one
    Where we look: Cable, breaker, starter and protection checked again for the new rating

  5. 05Load

    The driven machine

    The driven load determines the starting torque and speed profile the motor and drive have to handle. Pumps, fans, compressors and winches place different demands on the system, so starter selection and drive parameters follow the actual load.

    What the vessel sees: Current high across the whole speed range
    Where we look: Whether the cause is electrical or the machine is taking more power; a mechanical cause is passed to the mechanical contractor
    What the vessel sees: Pump on a drive hunts around its setpoint
    Where we look: Control loop settings, the feedback signal, the minimum speed
Drive replacement

Replacing an obsolete drive is more than a box swap

The replacement is selected around the motor and load that will remain. The old nameplate kW is only one input: motor full-load current, load torque and the overload required during starting all affect the drive rating. The enclosure has to fit the available space, and the heat rejected by the drive has to be removed by the room or cabinet ventilation.

An older motor and its cable may not have been selected for a modern inverter output. Fast switching can increase voltage stress on winding insulation, particularly with long motor cables, and can contribute to bearing currents. Depending on the motor and cable run, the solution may include an output filter, correctly terminated screened cable, or both.

The interfaces come next. Start, stop, speed reference, feedback and fault signals from the old drive are recorded and mapped to the replacement, and the new parameters are set for the motor and load before the first start. On the supply side, feeder protection is checked and the drive's harmonic impact on the vessel network is assessed, particularly where the system is generator-fed.

Scope

What we cover on each machine

Our scope stays on the electrical side of the equipment.

  • Generators: protection, AVR and excitation circuits, synchronising, load sharing, control interfaces
  • Motors: connection, protection, insulation checks, direction of rotation
  • Starters: direct-on-line, star-delta and soft starters
  • Drives: replacement, installation, parameter set-up, fault finding
Outside our scope

Work that stays with other specialists

We identify at the start when the job also needs another specialist.

  • Workshop rewinding of motors and alternators
  • Mechanical overhaul: bearings, alignment, balancing
  • Mechanical work on the engines
Related work

Related systems and services

FAQ

Before generator, motor or drive work

Is a failed bearing or a burnt winding something you repair?
Not as workshop or mechanical work. We diagnose the electrical fault and determine whether the machine can be put right on board. Rewinding, bearing replacement and mechanical overhaul remain workshop or mechanical work outside our scope.
Can a new drive be fitted to the existing motor?
Often, but only after the motor insulation, cable length, earthing and load requirements have been checked. An older motor may need an output filter or other mitigation, and in some cases replacing the motor with the drive is the better option. We establish that before the replacement drive is selected.
Load sharing was fine and then changed. Where do you start?
With what changed: a governor or AVR replaced, a set overhauled, a transducer or card renewed. We then record kW and kVAr on each set through a load change. That helps show whether the problem is on the active-power or reactive-power side, and which set needs further investigation.

Generator, motor or drive problem?

Send the vessel and machine details, what it is doing, and when the fault appears. Nameplate photos and the alarm or trip message are especially useful.