What is the best way to mount a Tecnadyne thruster to an ROV or AUV?
We recommend the tried and true approach — fabricate a saddle mount from aluminum, stainless steel or plastic material that will partially encircle the cylindrical portion of the motor housing. Use two screw drive hose clamps (stainless steel) to hold the thruster to the saddle mount. Put electrical heat shrink tubing around the hose clamps — this will protect the thruster housing. And place a thin pad of hard rubber between the thruster and the saddle mount. For more information this and other recommended mounting methods, please read the Application Note
What is the correct operating voltage range?
We recommend that you regulate the operating voltage to the thrusters so that it is within +/-15% of the rated voltage for that thruster. Remember, of course, that each model of the Tecnadyne thrusters is available at rated voltages from 48vdc to 330vdc (some models are available at rated voltages as low as 24vdc and some are available to 500vdc). For more information on this subject, please read Application Note
What are the recommended power supply requirements?
Tecnadyne thruster motors are designed to operate from a wide variety of power sources, including regulated DC power supplies, filtered and rectified AC and batteries. There are a couple of important precautions that must be taken – the power source must have some capacitance to help filter the back EMF from the motors and precautions must be taken to isolate the instrument level signals from the main thruster voltage and to prevent current loops. For a detailed explanation, please read Application Note and Application Note .
We plan to use computer with D/A card to drive the thruster control signals. However, the analog outputs from the D/A card are not isolated from one another and they are common to the computer chassis ground. Will this cause a problem?
Most likely, this will cause a problem with ground loops and noise – please refer to Application Note . Tecnadyne supplies an isolation card specifically intended to address this problem. This card, the ISO-4, is a 4-channel isolation amplifier that isolates four analog control signals (from your D/A card, for example) and also provides isolated 12vdc instrumentation power to four thrusters – it is highly recommended. Tecnadyne also supplies the ISOMOD-4, ISOMOD-6 & ISOMOD-8, which are 4-channel, 6-channel and 8-channel modules that package ISO-4 cards, with a capacitor bank, fuses and overvoltage protection in a 1-atmosphere housing depth rated to 2,000m. The ISOMOD-4, ISOMOD-6 & ISOMOD-8 can also be fitted with Tecnadyne’s ANALOG-8 card, which will control up to eight thrusters over an RS-232, RS-422 or RS-485 data link.
What type of maintenance is required for the thrusters?
Our thrusters are very low maintenance – simply remove the propeller and flush with fresh water after use. It takes about 30 seconds to do this with each thruster.
How do you remove the propeller?
On most Tecnadyne thrusters, the propellers are held in place with a simple E-clip that can be removed with the fingers or with a screwdriver. On the Model 260 & Model 300 thrusters, the propeller is held in place with a shoulder bolt that requires a 1/8in Allen key (provided with the thrusters) to remove.
Why is the magnetic coupling a benefit?
Using a magnetic coupling eliminates the rotating propeller shaft and the shaft seal which are the major cause of leaks and failures with traditional thrusters. The propeller shaft seals in use today were all designed for use at or near the surface where the pressure is relatively low – they inevitably fail when subjected to the pressure of typical ROV and AUV operations (100m to 10,000m). The magnetic couplings developed by Tecnadyne not only eliminate this common cause of failure, the larger sizes are able to reliably transmit over 20hp.
What is the life span of the thrusters?
The thrusters have an MTBF of 20,000 hours. However, it is very important to remember that the propeller bearings are lubricated by the sea water. If the sea water is clean, the bearings will last for 2,000 hours. If the sea water is sandy (when operating on the bottom) the bearing life is severely reduced. It is easy to check for propeller bearing wear, just by rocking the propeller back and forth. And replacing the bearings takes only several minutes and the bearings are really inexpensive.
What is the standard depth rating of the thrusters?
Most Tecnadyne thrusters have a standard depth rating of 750m. All Tecnadyne thrusters are available with depth ratings to full ocean depth. However, sales of some thrusters with depth ratings greater than 1,000m requires US Department of Commerce approval when these are shipped to some countries. Please consult the Tecnadyne factory for further information.
What is the standard voltage rating of the thrusters?
The standard voltage rating for most thrusters is 150vdc. For the larger thrusters (Model 2020 and above) the standard voltage rating is 260vdc to 300vdc. But Tecnadyne thrusters are available with voltages ranging from 24vdc to 500vdc (actual voltages available depends on the thruster model – please consult the data sheets).
Do you offer field spares kits?
Yes, please consult the factory.
What documentation is supplied with the thrusters?
All documentation is supplied on PC compatible CDRom. The supplied manual includes installation and integration instructions, field repair procedures, illustrated parts breakdown with parts list and schematics. We also include the final test reports for the thrusters.
Can I operate the thrusters out of water?
No! But if you do need to operate them out of water, do so for only a few seconds to verify that they are operating OK. If operated for too long, the sea water lubricated bearings will overheat.
What type of testing do you do on the thrusters before shipment?
Every Tecnadyne thruster goes through a rigorous test cycle. First, we test the electrical isolation of all subsea connector pins to the case of the thruster at 500v. Next, we pressure test the thruster in water to a pressure of 1000psi (7mPa). And then, we repeat the electrical isolation test (this will indicate any water leaks). Once we know the thruster is not leaking, it is placed in our water test tank and is operated for a period of 10 minutes to 1 hour at full power (smaller thrusters, such as the Model 260 are operated for 10 minutes and the larger thrusters, such as the Model 2020 and 8020, are operated for a full hour). We consider this test to be a break-in period. Finally, the thruster is operated throughout its normal operation cycle and all the performance data is collected and this is the final acceptance test of the thruster.
Can I do instantaneous reversals from full power forward to full power reverse?
No!! It is necessary that your system has a time based ramp from zero speed to full speed and from full speed to zero speed in both forward and reverse. If you are controlling the thrusters with hand operated joystick, the time required to move the joystick from one position to another is probably enough for the thrusters. However, if you are driving the thrusters with computer, it is essential that you program a linear ramp into the thruster control algorithm. The reason that this time based ramp is necessary is because the thrusters generate back EMF and the back EMF is much greater when the speed changes very rapidly. For example, if the time ramp from full power forward to full power reverse is 20ms, the back EMF current spikes will be 10-20 times greater than the steady state current (we have actually measured this). If this ramp is increased to 50ms, then the back EMF current spikes will be about 4-8 times the steady state current. And increase the ramp to over 100ms, and the current spikes will be about 2 times the steady state current. Make the ramp as long as you can and contact the factory if you have any questions.