Modifying a motor for series parallel operation

[zombiess]

I have a Cromotor Hubzilla that is setup for 17-18KV, it's only a 2 turn motor. I'm told I can modify the wiring and run it in series. If I wanted to do this how would I go about wiring this motor so it's setup in series and not such a heavy load on the controller. I'm thinking setting up a switching setup so I can go between series parallel if possible.

[amberwolf]

If the motor is wired up in groups of stator teeth, and then those groups are then wired up in parallel, you could just undo the parallel connections first, including the ones at the termination point (assuming it's Wye) where all the windings come together.

The series part I'm not exactly sure if it is as easy as then hooking one end of each group to the other, then rehooking up the loose ends of all together for a new termination point at the "center". Might require hooking them up in a specific pattern but since they are then series, it shouldn't, I'd think.

You *would* probably need to keep track of which windings had been paralleled, and only use those for their own series connections.

[ZOMGVTEK]

Generally the motor will have 6 windings that are twisted into 3 pairs. Break these pairs apart and run 6 phase wires out of the motor. Then you can do some snazzy switching for series/parallel.

Does the cromotor have an angled stator?

[zombiess]

Generally the motor will have 6 windings that are twisted into 3 pairs. Break these pairs apart and run 6 phase wires out of the motor. Then you can do some snazzy switching for series/parallel.

Does the cromotor have an angled stator?

No angled stator, same lamination style as a 9C.

I know doing some snazzy stuff is possible, but I'd need to know how to wire it in series after I break them into parallel groups.

If I don't sell this motor I'd like to at least do something interesting with it.

[ZOMGVTEK]

Crack the motor open, hope it has 6 clear phase wires twisted into 3 pairs, and label/pull them out of the hub. Find a big 3PDT contractor, and wire it up with some guessing and the help of other conversions on here. Doc has a diagram of how his was wired up somewhere...

http://www.endless-sphere.com/forums/vi ... f=2&t=9215

I would imagine its going to be made similar to most every other hub motor, so it might just be a simple matter of copying what other people have done and documented. However, this has never been done on this motor, so its going to be a bit of a learning process. Take some detailed pictures of the windings?

I'm a fan of the educated guess and check method. Sometimes it makes things blow up, but it usually ends up working. You can analyze why it worked after its working.

I'd want as much super low Z/ESR capacitance on the FET power rail as you can get to help manage the switching delay.

[John in CR]

There's a big thread about series/parallel and Delta/WYE. I'm not sure anyone has come up with something reliable at high power. DocBass tried it with big expensive contactors and ran into the problem of the spring loaded contactors losing contact in bumpy conditions.

[zombiess]

There's a big thread about series/parallel and Delta/WYE. I'm not sure anyone has come up with something reliable at high power. DocBass tried it with big expensive contactors and ran into the problem of the spring loaded contactors losing contact in bumpy conditions.

I would use large paralled fets to act as the switches.

[John in CR]

There's a big thread about series/parallel and Delta/WYE. I'm not sure anyone has come up with something reliable at high power. DocBass tried it with big expensive contactors and ran into the problem of the spring loaded contactors losing contact in bumpy conditions.

I would use large paralled fets to act as the switches.

I like the concept, and wondered about exactly that not long ago. Do they handle AC flowing thru them in the ON position?
Do they come in varieties with low enough resistance to make sense inside a hubbie and be absolutely reliable at hundreds of phase amps? If that really will work, then it's ridiculous that it's not already standard for DD hubmotors.

[zombiess]

I'd keep them external to keep heat down.

Now I'd like someone to tell me how to wire the windings into series.

[liveforphysics]

The 9C pattern doesn't repeat, so no chance of series/parallel IIRC.

You could perhaps delta-wye, but the bigger question is why.

That motor should be fantastic (equally fantastic as the other winds with equal copper fill), just needs to be powered at a lower voltage, and likely use a controller with 3077 FETs.

[John in CR]

Better hill climbing at lower speeds and more efficient take-offs or low speed cruising would be the only reasons for it. If the idea is to be able to run a 26" wheel, that's not going to work unless the bike is for highway speeds with a streamlined aero shell. Make it work well with only a few inches of added copper in the winding pathway, and you've got a high speed motor with much better efficiency in stop and go riding.

It needs to be done inside the motor. Otherwise you end up essentially adding a big chunk of efficiency robbing end windings, because you bring it out of the motor to make the correct connections only send it back into the motor through the other phase before coming back out to the controller.

John

[Arlo1]

I have a Cromotor Hubzilla that is setup for 17-18KV, it's only a 2 turn motor. I'm told I can modify the wiring and run it in series. If I wanted to do this how would I go about wiring this motor so it's setup in series and not such a heavy load on the controller. I'm thinking setting up a switching setup so I can go between series parallel if possible.

I am pretty sure it was proven there is nothing to gain from series parallel. Your motor will make the same thrust in series or parallel at low speeds it will only be easier on the controller to start in series but we up till now have been using some pretty barbaric controllers!

[John in CR]

Arlo,

That wasn't proven at all. The only thing proven was to eliminate the misconception that it would result in more torque. My high efficiency hubbies have series/parallel switching, and they're the only hubmotor to combine efficient mountain climbing with high speed on the flats. eg With my 360lb total load I can go 52mph on the flats in high (parallel) and climb 25% grades in low (series) without the sealed DD motor heating up using peak settings on the controller of only 5kw.

If it could be used on every takeoff, it would be another advantage by making acceleration more efficient for a high speed hubbie, since it would essentially be a low speed hubbie early in acceleration and get to its efficient band of operation quicker. Zombies's approach if done inside the hub, so there's no real detriment, could eliminate the limitations of the multiple contacts in my motors. If the switching was used on every takeoff, the wear on the contacts could become a problem. Those contacts and the flexible wiring that enable the switching are also a limitation for the max power you can push through these motors. A solution with mosfet could cure those issues.

John

[Olly3012]

Hi a silly idea I had was to replace the magnets altogether with electromagnets and then you would have a constantly variable Kv motor so you could essentially dial in the efficiency and speed.

[rkosiorek]

this modification can be done with any motor that is wound using an even number of multiple strands of smaller diameter wire instead of big fat wire.

for example. the Crystalyte 5302 motor has 2 turns per phase. those turns are wound from 8 parallel strands of 17AWG wire instead of some very large wire. these can be separated into 3 separate phase windings, each consisting of 8 parallel strands of smaller diameter wire. that is a total of 6 winding terminations.

now if you split each phase bundle of into 2 separate bundles of 4 strands each. we end up with twice as many bundles. 2 bundles per phase. each bundle is 2 turns.

if we connect those bundles in parallel we have a 2 turn motor. if we connect those bundles in series we end up with a 4 turn motor. this is how a series/parallel motor works.

a different approach that works with some motors is the Delta/Wye switch. the 3 phases of a motor can be connected either in a triangle (aka Delta) or star (aka Wye). the Wye works better at low rpms and the Delta runs 1.732X higher rpm for the same conditions.

rick

[rkosiorek]

I would use large paralled fets to act as the switches.

only complication is that the fets switch must be able to switch AC currents. standard fet relays and switches are dc only.

rick

[John in CR]

I would use large paralled fets to act as the switches.

only complication is that the fets switch must be able to switch AC currents. standard fet relays and switches are dc only.
rick

Darn, as little as I know about electronics I'm getting better at asking the right questions.

[scriewy]

sooo if our crystalyte 5404 is paralleled from the beginning, then all i can do is modify for series to make it slower.
how are most motors usually wound, parallel ? series just seems additional pain in the booty when you can start in the factory with wires and winds you want from beginning.

and what do manufacturers prefer to star-wey connect or triangle-delta or by design preference ?