Before the catalogue: the 5 tests that secure the reliability of FB submersible motors

Reliability is the main criterion when choosing a submersible motor. It must complete the job continuously and consistently, without interruptions or the need for special interventions, guaranteeing solid and long-lasting performance. For this reason, before an FB submersible motor enters the catalogue, we subject it to a sequence of tests that simulate the worst conditions and measure the aspects that really make the difference in the field. 

Each motor is tested for:

• Insulation, 

• Dielectric strength, 

• Mechanical resistance, 

• Pressure resistance, 

• Temperature resistance, 

• Minimum cooling, 

• Axial load, 

• Behaviour with high and low voltage, 

• Overload,

• Efficiency

How we test our submersible motors​

Each new type of FB submersible motor is put to the test in a testing environment that faithfully reproduces real operating conditions. The dynamometer bench with brake makes it possible to evaluate power and torque up to 220 kW, with voltage variation up to 1000V and frequency up to 60Hz. Motors are placed in boosters to simulate the minimum water flow around the motor, while precision instruments record data on insulation, dielectric strength, internal and external temperatures, and energy efficiency. 

In addition, the Test Room makes it possible to verify axial thrusts up to 250,000 N and temperatures up to 95°C at variable speed, evaluating critical components such as the thrust bearing. All these tests ensure that FB motors, in various types and with rated powers from 0.5 hp to 260 hp, are ready to work reliably and consistently. And when the motor reaches the hands of the end user, it can be relied upon for real, reliable, and catalogue-consistent performance, with no surprises or margins of error.

The tests FB submersible motors undergo after the winding phase

1) Insulation test - Checks the quality of the windings against moisture and water ingress, reducing the risk of failure and increasing long-term reliability.

2) Dielectric strength test (up to 2500V) - Applies high voltage to detect any insulation faults. 

3) No-load test - Verifies that the motor starts and runs correctly without load. It helps detect any friction or mechanical losses, ensuring smooth operation. 

4) Short-circuit test with locked rotor - Determines the maximum thermal resistance time of the motor under extreme conditions. It is useful for precisely setting electrical protections and provides additional indications in the event of anomalies, such as a possible pump blockage. 

5) Brake test at constant load and variable voltage - By varying the nominal voltage by ±20%, speed, torque, current absorption, power, and efficiency are recorded. This test confirms the correct operating point of the submersible motor calculated during the design phase. 

6) Brake test at variable load and constant voltage - By increasing the motor’s power load up to +25%, the temperatures reached are analysed, simulating possible anomalies such as closed valves, pumping sandy water, or off-curve operation of the electric pump. 

7) Power and efficiency test at different temperatures - Measures absorbed power, current, and efficiency both cold and hot, providing realistic data to estimate energy consumption and correctly size the electrical panel drive. 

Technical transparency: what’s needed for safe performance

FB provides customers, in the dedicated submersible motor catalogue, with a complete set of technical data and operating guidelines: power and efficiency curves, derating tables, protection and energy optimisation guidelines, application notes on minimum cooling flows, and maintenance instructions. 

The range includes rewindable water-filled motors from 6” to 10”, rewindable oil-filled motors from 4”, and resin-filled water-filled motors from 4” — all designed to ensure reliability, high performance, and easy maintenance. 

Each motor is verified down to the smallest detail before reaching the field, thanks to a combination of in-room and test room trials, thus ensuring that the catalogue data truly reflects actual operating performance.