JeftK
New member
Hi, I want to control the maxpower ct80 bowthruster by using a pwm controller. Does anyone know if this is possible and maybe give me a few hints? Thank you.
PWM controller
- Thread starter JeftK
- Start date
coopec
N/A
Are you serious?
We get quite a few prankster posing mischievous questions.
Can you tell us where you are from.
What sort of boat you have.
What PWM controller you have in mind?
JeftK
New member
Hi, of course I am serious! I'm from the Netherlands. I have an 8 meter long motorboat and the problem I have with the bow thruster is that it is to digital (only on or off). I've a 300 amps reversible PWM controller. If you have some hints for me I would be very grateful.
Alex_Blackwood
Well-known member
Takes one to know one!
andsarkit
Well-known member
Certainly possible but not a sensible idea. DC motor controllers usually work at much higher voltages than 12v to keep the currents down. Trying to switch 100+ amps requires very large transistors and associated heatsinks with quite large losses. A stalled motor has a very low DC resistance and will draw up to 5 times the running current when it starts. Motors rely on the back EMF generated when it is running to limit the current. If you are running it at slow speed you would have to take this into account. You would probably need a tacho feedback to properly control it.
I have been involved in the development of AC motor controllers for up to 500kW motors and it is quite scary when they draw 6000A on start up. There was a lot of software development for the controllers and if it didn't get the timing exactly right the results could be quite lumpy.
I doubt you would find anything off the shelf and it may invalidate the bowthruster warranty.
Some information here EV controller
You might be able to find a controller off a golf cart or mobility scooter that may work.
The sensible way to do it would be an AC motor and variable frequency inverter but most people manage quite well giving short bursts on the bowthruster.
There are people on here that know a lot about EV cars and can probably tell you how the car industry controls a motor from battery power.
I have been involved in the development of AC motor controllers for up to 500kW motors and it is quite scary when they draw 6000A on start up. There was a lot of software development for the controllers and if it didn't get the timing exactly right the results could be quite lumpy.
I doubt you would find anything off the shelf and it may invalidate the bowthruster warranty.
Some information here EV controller
You might be able to find a controller off a golf cart or mobility scooter that may work.
The sensible way to do it would be an AC motor and variable frequency inverter but most people manage quite well giving short bursts on the bowthruster.
There are people on here that know a lot about EV cars and can probably tell you how the car industry controls a motor from battery power.
vas
Well-known member
agree with previous posters on this being a non-sensible idea.
HOWEVER, you could go hydraulic: motor (tiny compared to the massive DC, el.motors!) BUT with the extra complication that you need a PTO (power take off) on your engine (or pulley/clutch assemby on the front of it), and lots of pipes going back and forth.
Controlling can be v.cheap afterwards with a progressive diverter valve thingie.
V
HOWEVER, you could go hydraulic: motor (tiny compared to the massive DC, el.motors!) BUT with the extra complication that you need a PTO (power take off) on your engine (or pulley/clutch assemby on the front of it), and lots of pipes going back and forth.
Controlling can be v.cheap afterwards with a progressive diverter valve thingie.
V
JeftK
New member
Thank you for your reply! Indeed the thruster has a 24V motor and the average current is below 150 amps, peak current should be 200 Amps or less on power up it takes 400 amps. The controller I want to use is from a mobilty scooter. I just don't know how to connect this thing. I tried yesterday but it didn't work out.
Alex_Blackwood
Well-known member
Agree with previous answers. However a lot more detail of the controller would be required for any sensible comment. I assume that the scooter control has reversing capability?
JeftK
New member
Hi Alex thank you for your reply. The controller I want to use is a 24V 300Amps controller it has reversing capability. I can control the output by joystick or a pwm signal. In joystick mode the output is 0% if in middle position and up to 98% from middle to left or middle to right position. It worked fine when I used it on a scooter but I just don't know how to connect to the thruster. I've never seen such a motor. 2 positive connections 1 negative with a big relay.
andsarkit
Well-known member
You could make up a load such as a couple of 12v car headlight bulbs in series and connect to the controller output. Connect a voltmeter to the output and see what happens when you adjust the controller. Ideally you would use an oscilloscope but a simple multimeter should give you some useful information.
andsarkit
Well-known member
Do you have a circuit diagram for the original bowthruster wiring or can you let us know the make and model number?
The 2 positive connections might be for reversing or do you have a polarity changing contactor/relay?
The 2 positive connections might be for reversing or do you have a polarity changing contactor/relay?
JeftK
New member
hi Andsarkit, thank you for your reply. A voltmeter won't do, it will always read 24 volts but the oscilloscope shows a very nice block wave with a duty cycle from ~5% up to ~98% in both directions. So I know the controller is in good shape.
Alex_Blackwood
Well-known member
Just off the top of my head, I may be wrong! I think that the motor may be your problem. I suspect that the controller has one output which reverses according to the position, right or left, of the joystick. The motor has two + ve. and one - Ve. used to determine direction dependent on which + Ve. is energised by the relay. Cannot say much more without eyeballing the motor depending on the winding configuration you may be on to a loser. Again one of these that is difficult to provide a definitive answer for on line. Sorry, Having said that don't be surprise if someone with more experience of this equipment doesn't pop up.
+1 for any circuit diagrams or documentation.
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JeftK
New member
The make is Powermax model is ct80. I think that you are right concerning the positive connections. I think that the relay attached places the motor in forward or reverse(left or right) but it must also have an inhibit function. I connected the controller yesterday to one of the positive connectors and to the negative but nothing happened. (sorry for my bad English, it has been a while :-( )
You can get the diagram from here: max-power.com/product/164-electric-tunnel-thrusters/5113-electric-tunnel-thruster-ct-80 only pdf. I have the 24 volt version.
Tranona
Well-known member
Bow thrusters have always been switched, usually by relays one way or the other rather than variable as you are aiming at. It is desirable to have variable speed but if it was easy manufacturers would have done it years ago. In fact Sleipner have recently brought variable control sleipnergroup.com/knowledge-hub/thrusters/thruster-blog-articles/five-benefits-with-variable-speed-control
It sells at more than 50%premium over the standard units and I believe they will be offering conversion kits for existing models soon.
So, not sure a simple control such as you are suggesting would do the job. However I am not up with exactly how the motor is reversed except that the relays in the control box switch the current from one positive to the other through relays.
It sells at more than 50%premium over the standard units and I believe they will be offering conversion kits for existing models soon.
So, not sure a simple control such as you are suggesting would do the job. However I am not up with exactly how the motor is reversed except that the relays in the control box switch the current from one positive to the other through relays.
JeftK
New member
thank you, that are the exact reasons I want the thruster become speed-controlled.
andsarkit
Well-known member
It looks like the main power connections are fixed and the reversing is done by relays controlled by the brown or blue wires. I've no idea what the third main connection is for unless it is for a different voltage rating.
The handbook mentions having a separate controller supply and a main positive isolating relay which will need to be energised to send power to the motor. The controller will then energise either the blue/black or brown/black wires to select the direction. Not both together or there will be a big bang. There may even be a mechanical interlock to prevent this happening. The original system has a built in delay so you can't change direction without a pause.
Once one of the reversing relays is energised it may be possible to then do the reversing with your external mobility scooter controller.
If you have the original controller working you could leave the main bowthruster power off and just see what voltages you get on the blue/black and brown/black wires when you operate the controller. You might also hear a relay clicking.
Just be aware that you are dealing with potentially very high currents and if you get something wrong there will be a possibility of damage or injury.
By the way, your English is excellent and a million times better than my Dutch although I have been to Holland many times.
ean_p
Well-known member
Have a lookie here...https://www.youtube.com/watch?v=8IYVUyf_rYE
The world of electric hand pallet trucks etc is exactly what your trying to replicate.
Essentially direction is via interlocked ( so only one can ever be energised at any one time) contactors and traction rate is via the pulsed controller, or as in yesteryear by taking out of line a series of resistance's which give a stepped acceleration now long replaced with first the old thyristor controllers and then Mosfet controllers.....its been a few ( a good few ) since I dabbled in them but sounds very do'able if you can be inclined. Don't know what help the video will be but any good circuit diagrams will give you the idea if you sweep out all the auxiliary circuits and just focus on the 'traction' circuits.
The world of electric hand pallet trucks etc is exactly what your trying to replicate.
Essentially direction is via interlocked ( so only one can ever be energised at any one time) contactors and traction rate is via the pulsed controller, or as in yesteryear by taking out of line a series of resistance's which give a stepped acceleration now long replaced with first the old thyristor controllers and then Mosfet controllers.....its been a few ( a good few ) since I dabbled in them but sounds very do'able if you can be inclined. Don't know what help the video will be but any good circuit diagrams will give you the idea if you sweep out all the auxiliary circuits and just focus on the 'traction' circuits.
Alex_Blackwood
Well-known member
As with the above I am unsure of the three wire configuration. Perhaps, and only perhaps, these motors have two separate field windings for direction?? To change direction you need to reverse the +ve and - ve through either the armature or field, or both depending on winding arrangement. Which would need either a two or four wire arrangement. Just possible it may be a permanent magnet design for which three wires would work, I think!! The diagrams don't show the actual motor configuration. Considering the other interlocking circuits which are used. I am of the opinion that your idea is just not practible without considerable alteration and redesign of the system.
I am now searching for for more info on the motor design. Curiosity has kicked in.
Edit. Scrub the permanent magnet idea. Won't work!.
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William_H
Well-known member
It all seems very complicated especially as you do not know the arrangement that was used in the scooter motor for this controller. Even if you got it going it may well be destroyed by back EMF. I would suggest perhaps a mediocre solution might be to fit a resistor in the negative or positive supply to reduce the speed and then add a relay across the resistor to give choice of full or partial power. Resistor could be in the form of stainless steel plate where distance between bolt hole connections and width and thickness of plate determine resistance so speed on low. I would start with 18g ss 10cm between bolt holes and 30mm wide. See how that looks for resistance. ol'will
