Marine Motors and Certificates

Marine & Offshore

The mechanical and electrical performance of the basic rotor nl® electric motors is adapted for marine and offshore application. Due to often aggressive “salty” environment, almost all sizes of RN series can be supplied in cast iron motor housing and end shields. rotor nl® produces electric motors for below deck as well as above deck applications and they can be equipped with disc brakes, encoders, force ventilation units etc. The electric motor windings are based on ambient temperatures of up to 50°C and are moisture and mould resistant suitable for relative air humidity up to 96%. These electric motors meet various criteria set out by a number of marine classification societies and are suitable for “essential service” when supplied with a marine certificate.

How can a rotor nl®electric motor be identified as a marine motor?

All rotor nl® marine electric motors are equipped with stainless steel rating plate that specifies the following:

  • the nominal electric motor data and the “rotor nl® marine classification” marking
  • any additional rating plates with supplementary/customer data


The rating plate specifies the marine classification society and the ambient temperature specified by the society’s regulations (usually IEC92.301 C). The date of purchase as well as the marine certificate number (issued by the marine classification society) are also marked on the rating plate. The rating plate and a fixed component of the electric motor would have been certified and stamped by the marine classification society surveyor when marine approval testing is required. Should no marine approval testing be required only the “marine classification society” logo and the date of production would be specified on the rating plate. No additional rating plate would be fitted. Electric motors with a rating plate that is not marked as ‘rotor nl® marine classification’ are not marine motors and even though it is very likely that they would operate satisfactorily in the marine environment (on-board of a vessel or offshore), a factory marine motor declaration cannot be issued. A 2.1 or 2.2 class certificate can, in most cases, be issued for marine motors that are not older than one year upon request and the necessary data submission. The temperature rise of the winding must be determined by the resistance method. There are certain specific regulations applicable on marine motors related to the mechanical execution.


All rotor nl® electric motors are tested after assembly to guarantee their correct operation and are subject to high-voltage insulation and no-load run tests. Additional tests can be performed in the factory test laboratory. Multiple electric motors can be tested there under continuous or intermittent load at the same time and their electrical and mechanical properties measured and identified. This is the same procedure as when new motor designs are tested and Type Test Reports issued. Rotor nl® electric motors can also be supplied with a factory declaration of compliance or with a test certificate that confirms that the test data measured on a specific electric motor are in compliance with the customer’s specification. Rotor nl® electric motors are tested to the EN 10204 standard and 4 different certificates can be selected mentioned below.

EN 10204-2.1

The declaration of compliance 2.1 (factory declaration) is issued based on the electric motor serial number, invoice number and the customer order number. No testing is involved when issuing this document.

EN 10204-2.2

Test certificate 2.2 (factory issued certificate) is issued based on the electric motor data set out in the type test report (when the motor prototype have been tested) amended with certain other data (historical test data). The invoice number and the customer order number are also marked in the test certificate. A number of motor serial numbers of the same type can be included in one test certificate.

EN 10204-3.1

The relevant no-load or full-load tests are carried out on a specific electric motor when the inspection certificate 3.1 (inspection report) is issued. This must be clear at the moment of the order placement. This test is also referred to as the “routine test” and provides a reasonable guarantee of the correct performance of the electric motor when the tested data comply with the type test data. The invoice number and the customer order number are also marked in the inspection certificate. One inspection certificate is issued for each electric motor.

EN 10204-3.2

Inspection certificate 3.2 is issued based on the test witnessed by an independent inspector (classified inspection­ report). The inspector (surveyor) can be appointed by the customer or by ourselves. In majority of the cases the surveyor would attend the testing in our approved test laboratory. External testing by certified laboratories have to be carried out in certain cases.

Type approval certificate

Rotor nl® is authorised and approved to independently test and certify electric motors up to 300 kW (without the actual presence of a surveyor). The tests are carried out in our approved test laboratory. This enables rotor nl® to supply electric motors for essential service quickly and with the relevant certificate. The independent testing has been arranged with a number of classification societies. Rotor nl® can currently issue type approval certificate for DNV, BV, CCS, Lloyd’s, ABS, GL and RMRS.

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