About the wiring, shouldn't it be star point to NC, delta point to NO, COM to controller phase wire and the coil + and - to a 48v power source with a switch?
Afaik, the common is just a wire that connects all the end points together. You could hook a neuter upto this but it's not necessary.
The controller (thing that turns DC into 3 phase AC) is just that, something that turns DC into 3p AC, it will be fed with 2 wires, positive pole and negatie pole (3 if you count ground), then from the controller 3 wires will leave, your 3 phases that the controller has created. These will be hooked up to one end of the motor windings. The other end of the motor winding will be daisychained together, thus creating your star point.
In order to switch to delta, you'll need to splice into the daisy chained wire on the other end of the windings, connect those to your NC pole and the INPUT of the relay to another windings star point, do this for all three windings and all three relays (provided you use 3 relays, if you use more you'll need to do more daisychaining), so you essentially create the daisy chained star point again, but this time with an interrupter inbetween.
Then you will have to daisychain your L1, L2 and L3 (3p coming from controller) to the NO contact of the relay. You'll have to match up the phases so each winding gets two different phases (L1 + L2, L2 + L3, L1 + L3), and you'll have to get the phase angle correct or the motor will run backwards (if it does you simply switch out one phase with another and it should correct it).
The two 48V DC connection coming from the battery you will then hook up to the relays coils with a switch of some sort in between, then when you push that switch, you'll go from star to delta.
Current draw will be higher in delta 88v * SQRT3 = 152V * 45A (what your motor can/will draw) = 6.8Kw. As opposed to star configuration; 88v * 45A = 3.9Kw. Alternatively you can see this as, 88v * 45A*SQRT3 = 6.8Kw. You cannot "up" the amperage of the motor as it's simply it's physical limit, however if you switch to delta, the voltage to the windings increases and this the motor will be able to put more power through it's windings, resulting in higher draw from the source, 77 amps to be exact. Essentially what you are doing is lowering the resistance of the motor to pass more power.
I'm really not sure you want to do this... exploding lithium batteries are nasty, and what about the controller, can is handle the extra draw?
Also, concerning the voltage increase in delta; considering your motor is currently hooked up in a star configuration, it's likely that the controller is kicking up the output voltage to the motor, if you hook up a star then line to line Voltage becomes /SQRT3 over the coils, THUS to get 88v over your coils, the controller would have to be putting out 152V line to line, if you then switch to delta, the motor will be receiving 152V, as you've disconnected the "common" (star point) and replaced it with a line voltage on a different phase angle.
It's also possible that your motor is simply "rated" 88v, meaning there is 88v/SQRT3 over the coils or 50v. You need to figure this out before you try this.
Are you sure about the voltage? is it the same with DC motors? btw, why is it called a DC motor if inside the motor it's actually AC?
The laws of physics don't change for different motors
It's called a "DC" motor because you feed it DC (but the integrated controller changes that to AC).
The motor can handle that for a short period, it's about 6700 watts but I hope it isn't so with the voltage raise.
It is, if you switch to delta the motor will be receiving 152v, (or 88v depending on what the actual line to line coming from the controller is). I know motors are robust and can handle overvolt for a short while, but there is other components involved as well, the controller for ex, or the battery, it will get smoking hot... you might want to think about thermal management, and maybe overheat protection.
http://www.allaboutcircuits.com/tex...t/chpt-10/three-phase-y-delta-configurations/
http://www.allaboutcircuits.com/tex...t/chpt-10/three-phase-y-delta-configurations/
Quote from that link:
"In balanced “Y” circuits, line
voltage is equal to phase
voltage times the square root of 3, while line current is equal to phase current. In balanced Δ circuits, line
voltage is equal to phase
voltage, while line current is equal to phase current times the square root of 3."
Does it mean that in star (Y) the voltage is raised to about 152v inside the motor and current stays the same while in delta the voltage stays the same and the current is raised to about 77A? how can a 45A controller give more amps then it's rating? I don't get that part...
It means that in star the voltage inside the motor will be /SQRT3 or 88v, while the current is (max) 45A, while in delta the voltage is simply supplied to the motor as line voltage (152v) and the current (max) draw will be 77A. The controller will be made to work outside of spec, just like everything else in this setup. The controller is most likely an IC, it will do whatever you tell it to do up to the point you get white smoke.
What i'm trying to tell you, is that what you are doing is not "kosher" and sooner or later you will destroy the E-bike because of this.
The proper way to do this would be with higher spec parts. Get a more powerful motor and extra battery pack, then you can simply have the motor run below spec while in star configuration and at spec when in delta.
You never get something for nothing, if you want more power out of something that isn't rated for it, you'll get more heat, sparks, exponential wear and eventually white smoke.