top of page

Yacht Monitoring & Control System: A Visit to Praxis Automation - Part 1

Updated: Mar 23

Our monitoring and control system partner is Praxis Automation from Leiden in the Netherlands.

Dutch people seem born with two charms attached, bicycles and boats, so when it comes to yacht equipment, they are top of their game in most ways. It was a two-day visit to inspect a simulation of the final scope of delivery and the software package in its preliminary form. After an initial introduction, we got down to business, starting with the drive line.

Explorer Yacht Monitoring & Control System

Our explorer yacht has a duplicated driveline similar to the illustration above; we will look at a single side for now. We have a John Deere 4045 diesel feeding through a clutch into a mechanical step-down drive PHT from Esco Power. This drive connects the hybrid motor to the driveline allowing it to run at higher than engine speed. The drive line then passes to a Twin Disc gearbox before going through a self-aligning coupling and onto the propeller shaft. So far, so good.

Operating modes are as follows:

  • 100% diesel driving the propeller, engaged clutch, gearbox engaged or disengaged

  • 100% electric - diesel clutch disengaged, gearbox engaged

  • diesel and electric - basically everything running.

  • Finally, in generating mode charging batteries from the diesel with or without the propeller connected and spinning.

Table 1 shows the various ratio involved, along with some governing performance parameters. Our next task was to run through the various operating modes and consider how they perform with time when loaded, unloaded, or poorly treated. There is no right or wrong here, but it is worth a look. Firstly we checked the various speed limitations.


1500-3600 RPM max

30kW power - 90kW generation


1000 - 2300 RPM max

120kW max, clutch to PHT, fixed to E-motor and gearbox.


fixed 1.46 (not as thought 1.7)

250kW max


2.5 to 1 step down

250kW max, F/N/R

Problem - early documentation for the PHT drive indicated a gear ratio of 1.7:1 or 1.46:1 2300x1.7=3910 >3600 RPM limit on the E-motor, so we have an immediate problem!