{"id":16,"date":"2019-08-21T10:46:41","date_gmt":"2019-08-21T10:46:41","guid":{"rendered":"http:\/\/hansfix.nl\/electric\/?p=16"},"modified":"2019-08-21T13:33:16","modified_gmt":"2019-08-21T13:33:16","slug":"motor-controller","status":"publish","type":"post","link":"https:\/\/hansfix.nl\/electric\/2019\/08\/21\/motor-controller\/","title":{"rendered":"Motor controller"},"content":{"rendered":"\n

To control the speed of the motor, you ‘ll need a controller. And some additional hardware… Of course it is possible to build these parts completely yourself, but the currents in part of this hardware is so high, that any small mistake will lead to a small cloud of smoke. Remember, the motor is 10 kW, at appox. 48V, this gives a current of 200 A! To prevent to much smoke (after the magic smoke has escaped the things don’t work any more) I went looking for a controller, again on marktplaats.nl I found a Sevcon MOS90 controller, again this is from an old fork lift. The only problem was, I couldn’t test it and couldn’t get it to work. So I contacted HSCT and they helped me. It proved that I didn’t connect it correctly, because when I connected it according to there circuit diagram it worked perfectly. They also adapted the settings a little bit (ax current 300A e.g.). It seems that I also have the most robust one, the one that can handle up to 400A!<\/p>\n\n\n\n

\"\"
Sevcon MOS90 motor controller.<\/figcaption><\/figure>\n\n\n\n

So that is the base of the controller, but with that controller, it can only run in one direction, so you need a heavy relay (and heavy relays are called contactors) to switch the polarity of one of the windings in the motor. In a series motor there are two: the stator and the rotor, if you change the polarity of one of them, the motor runs in the other direction. If you change both, the motor runs in the same direction again.<\/p>\n\n\n\n

\"\"
Motor with modified connections for stator and rotor. Also visible the contactor to change direction.<\/figcaption><\/figure>\n\n\n\n

Because this motor was build to drive an oil pump, it was not possible to change the polarity of one of the windings, only both at the same time. That doesn’t make sense, so somehow I had to break the connection of the two windings, and get the wires to outside the motor, to connect to the contactor. Luckily this was not to difficult, the wires were easy accessible and two connections were made on a small piece of trespa. So now we had the possibility to let it run in two directions (with a switch), and control the speed with a potentiometer. Not optimal, but workable.<\/p>\n\n\n\n

On a boat (and also on It Paradyske) it is normal to have a single lever throttle control. If you move the lever forward, the motor runs forward, and if you pull it backwards, the motor spins the other way round, the further you push the lever, the harder it spins. Yes, fine, but the potentiometer doesn’t work that way, it only controls fast and slow, and the direction is controlled via a double throw switch, how to adapt this?<\/p>\n\n\n\n

One way is to solve it in a mechanical way, but wait, I am a software engineer, and also studied electronics, so why not…?
Yes, solve it in a smart way. Get a microcontroller, a throttle lever, and some nice gadgets (remote control), do a little bit of mechanical modification to the lever and write some software to glue it all together.<\/p>\n\n\n\n

\"\"
Mechanical push pull wires removed, and potentiometer added to throttle lever. This is an almost identical throttle control as mounted on It Paradyske, so I hope this one will fit flawlessly. <\/figcaption><\/figure>\n\n\n\n

One of the options I didn’t mention yet, is the possibility to use a 0-5V voltage level to control the speed of the motor via the MOS90 controller. So basically the microcontroller reads the position of the lever, determines which side of the direction contactor should be activated, instead of a double throw switch some relays are used to control this, and controls with an analogue output the speed of the motor.
Of course there are some nice to have things: Standing on the pulpit, and controlling the speed when docking! So a simple remote control was added.<\/p>\n\n\n\n