2 wire vs 3 wire windlass

[44kebeck]

I have an older Lofrans windlass with 3 terminals. (neg, pos up, pos down)

Since most DC motors reverse by switching polarity, I'm curious about what's going on inside the Lofrans motor. (separate windings?)

Thanks in advance for any insight

[sailormed]

I just goog... it and found tens and tens of drawings and comments.

[44kebeck]

I googled it too and found all the diagrams but nothing that explained the internals of a 2 vs 3 wire motor.

[Bycrick]

A two-wire motor is a simply reverses the polarity to the two motor connections (one winding) to reverse the direction. That usually requires a more complicated solenoid. Or you can build a two winding motor using one at a time for the two directions.

[44kebeck]

That's what I was thinking - simplifies the switching. Allows for 2 simple SPST foot switches if you aren't using solenoids.


So electro mechanically there is no advantage one over the other except that the 2 wire motor can have a bigger winding since there is only one (or the motor could be smaller)

[roland stockham]

Just a theoretical idea but if a motor has bigger windings I would expect t to take longer to bothe heat up and cool down so it could effect the duty cycle.

[onavegador]

your foot switches will not live a long if you use no solenoid eg. for a winch with 800 Watts or even more. Where is a huge current passing the contacts of the switch when braking the anchor out of the sea bed. And solenoids for up and down does not cost a fortune. Just shop a little around.

Good luck
James

[44kebeck]

I'm not a fan of foot switches either.

I've been looking into this further and now understand that the 3 terminal motor is a series wound motor.

"With a series wound motor, the field coils are connected in series with the armature coil. Series wound motors are powerful and efficient at high speed and generate the most torque for a given current. A series wound motor will uses more current over a permanent magnet motor because they use field coils to generate a magnetic field. Series wound winches are heavier duty winches, and tend to be more expensive."

"A permanent magnetic motor will pull the same as a series wound motor, at at less of an amperage draw on the battery and charging system. However, as the permanent magnet motor gets warmer, the power will drop as the amperage draw will increase. The amperage draw on a series wound motor will stay the same throughout the duty cycle."

You have to reverse the current in the field coils to reverse the motor

[blubaju]

Originally Posted by 44kebeck

I have an older Lofrans windlass with 3 terminals. (neg, pos up, pos down)

Since most DC motors reverse by switching polarity, I'm curious about what's going on inside the Lofrans motor. (separate windings?)

Thanks in advance for any insight

Same here, unfortunately I had water entry in the stainless base, coals & everything inside completely corroded, ordered new 1000W motor in Italy, received twice a wrong one, despite sending pictures & drawings, surprisingly all same spare part number.



The dimensionally matching replacement has 2 contacts only, needed new solenoid of course for reversing polarity.



Take much care about rust between the aluminum housing and the steel motor, I had to break down the motor and carefully chisel away the rust in that small gap. No other way to separate motor and windlass. Else the motor looked like new outside. There supposed to be a small drainage hole at the bottom

[Jim Cate]

Originally Posted by onavegador

your foot switches will not live a long if you use no solenoid eg. for a winch with 800 Watts or even more. Where is a huge current passing the contacts of the switch when braking the anchor out of the sea bed. And solenoids for up and down does not cost a fortune. Just shop a little around.

Good luck
James

We keep getting this statement here on CF, and it is simply untrue. IF you get foot switches that are designed for the job, they are very reliable and long lasting. The ones supplied with Maxwell windlasses, for instance... the ones on our boat are now 30 years old for the up switch and 17 for the down switch and have never given any problems.

Solenoids are not without flaws, you know, and have their own list of failure modes. One that has been mentioned here is inadvertent activation, raising the anchor when not desired... never happens with direct switching.

Your choice!

Jim

[RaymondR]

As Jim says, two good reliable, quality, foot switches and two sets of windings in the three terminal motor is a far more reliable combination than a single set of windings and the two switches and four solenoids required with a two terminal motor.

[Jammer]

Originally Posted by 44kebeck

I have an older Lofrans windlass with 3 terminals. (neg, pos up, pos down)

Since most DC motors reverse by switching polarity, I'm curious about what's going on inside the Lofrans motor. (separate windings?)

Thanks in advance for any insight

Contrary to long-standing tradition on Cruiser's Forum, I am actually answering the question you asked.



DC windlass motors that reverse by using three terminals are series wound, that is, the field winding is in series with the armature. Series wound motors operate in the same direction when polarity is reversed, because the polarity of the field and the polarity of the armature both change.


Therefore, reversible series wound motors have two field coils, wound (well, connected) in opposite directions -- in this case, an "up" coil and a "down" coil. One end of each field coil goes to the armature. The other end goes to the "up" or "down" terminal -- "up" for the "up" coil and vice versa.


The terminal you call the "negative" terminal is actually better understood as the "common" or "armature" terminal, again, because the windlass will work the same way if you switch polarities and use that as the "positive" terminal. In other words, the "up" terminal is still "up."



Series wound motors have the desirable property of producing more torque when heavily loaded and a self-regulated maximum speed, which is why they are used for windlasses. Permanent magnet motors produce constant torque regardless of load and have no upper bound on speed when run unloaded (until they self destruct or the internal friction increases to the point where it matches the output torque).


Another type, shunt wound, is similar to permanent magnet motors in performance but also requires a three-terminal arrangement for reversing. They are not used for windlasses.


You may now resume your regularly scheduled conversation on tangentially related matters.

[RaymondR]

Originally Posted by Jammer

Contrary to long-standing tradition on Cruiser's Forum, I am actually answering the question you asked.



DC windlass motors that reverse by using three terminals are series wound, that is, the field winding is in series with the armature. Series wound motors operate in the same direction when polarity is reversed, because the polarity of the field and the polarity of the armature both change.


Therefore, reversible series wound motors have two field coils, wound (well, connected) in opposite directions -- in this case, an "up" coil and a "down" coil. One end of each field coil goes to the armature. The other end goes to the "up" or "down" terminal -- "up" for the "up" coil and vice versa.


The terminal you call the "negative" terminal is actually better understood as the "common" or "armature" terminal, again, because the windlass will work the same way if you switch polarities and use that as the "positive" terminal. In other words, the "up" terminal is still "up."



Series wound motors have the desirable property of producing more torque when heavily loaded and a self-regulated maximum speed, which is why they are used for windlasses. Permanent magnet motors produce constant torque regardless of load and have no upper bound on speed when run unloaded (until they self destruct or the internal friction increases to the point where it matches the output torque).


Another type, shunt wound, is similar to permanent magnet motors in performance but also requires a three-terminal arrangement for reversing. They are not used for windlasses.


You may now resume your regularly scheduled conversation on tangentially related matters.

Due to lock-down and all the entertainment venues being shut down my alcohol consumption has increased and I've had a few beers and am now working on a rum and ginger beer and consequently these circumstances allied with my advancing age deter me from applying any degree of intellectual rigor to a technical analysis of your post.

However befuddled as I am, and mindful of the attentions of the moderators and disinclined to be disagreeable, I have an overwhelming feeling that your post includes elements of BS in respect of the arrangements of the field and rotor coils and their interactions in a series wound motor.

I have this vague recollection that the windings in a three terminal motor are arranged so that positive to common on one side makes the motor rotate one way and that positive to common on the other makes it rotate the other way. That is that the field windings are arranged so that two of them and two of the brush timed commutating rotor current induced magnetic field one way and the other the other.

Of course it could be just the rum talking

[Jammer]

Originally Posted by Jim Cate

Solenoids are not without flaws, you know, and have their own list of failure modes. One that has been mentioned here is inadvertent activation, raising the anchor when not desired... never happens with direct switching.

Jim,


While I agree with your overall point I would like to suggest that direct switching is not foolproof. While I am unaware of any examples involving windlasses on yachts in particular, momentary switches do fail shut leading to unwanted activation, just as relays and contactors do. The most common situation is a failure of the switch to open when it is released but other failures are possible and do occur.


There are two common safer-design practices used on industrial hoists to mitigate these failures. Again, they apply equally with relays and with direct switching:


1) An emergency stop switch is provided in addition to the up and down switches. These are push-to-break switches and are much less likely to fail shut than push-to-make switches.


2) An "operate" switch is provided that is in series with the "up" and "down" switches. The idea is you hold down both the "operate" and one of the direction switches at the same time. If, say, the "up" switch fails shut then the machine will still stop when the "operate" switch is released.


With foot operated switches, the idea is that you place the switches so that you can depress both "operate" and either "up" or "down" with one foot.

[RaymondR]

The for deck of a sail boat is not the best environment for an excessive number of switches from both operation or maintenance viewpoints.

The winch will either run all the chain out, in which case one hopes that the bitter end is shackled to something substantial in the bottom of the locker, or all the way in, in which case the anchor will rack and one hopes the bow is not going to concertina. And, in either event one hopes that the fuse will blow or the breaker kick out.