Series or Sepex?

[miketuite]

Hi,

I tried searching for an answer, but no luck. What's the difference between series and sepex systems? Which do I have in my '03 G22E?

Thanks,

Mike

[cgtech]

All yamaha electric G19e and newer are "sepex". All yamaha electrics prior are "series". A brushed dc motor (like all traditional DC golfcart motors) has three major component systems.

1- the "rotor" or armature- This is the part that spins and moves the cart, the portion that is acted upon by the magnetic field created by the power consumed in the motor.

2- the "stator" or field windings and shoes- this portion is bolted into the outer shell of the motor, it is stationary (it better be, or $$$). Power passes through it to create a magnetic field that applys torque on the rotor.

3- the brushes and brush-holder- these brushes supply power to the rotor with a long wearing but reletively soft carbon/graphite conductor that will do its job while allowing the rotor to spin. This part is electrically isolated from the outer shell, and all four brushes are isolated into groups of two. Each brush has its pair 180° away, with the two pairs 90° seperated. The brush orientation is of little concern in this discussion, they are the same in both series and sepex motors.

On a traditional Series motor, all the voltage and current will pass through the field and armature. One circuit, like a loop inside the motor. To achieve reverse, the F&R flips power to two of the high current wires to reverse polarity and the magnetic field. If reverse were not needed, like a pump application, this type of motor would only need 2 cables.

On a Sepex motor, the armature (rotor) and field (stator) are treated as two different circuits. The field windings are never fed full voltage or amperage that is fed to the armature, field windings are much finer wire than a series motor field winding. they make up for this by having many more "turns", a longer wire to give a near equivelant amount of magnetic force with less amps. Another major difference from a series motor is the method to achieve reverse, the field circuit is reversed polarity within the motor controller, as opposed to a mechanical method of reversing polarity (lever actuated rotary switch, or two extra relays to "flip" the polarity). The "seperate" nature of the field circuit allows the controller to turn the spinning armature into a generator to apply power back into the batteries when braking by reversing the field polarity in a controlled fashion. If this were attempted with a "series" motor (equal volts and amps to the field and armature), the results could be catastrophic, and at minimum not comfortable or controlled.

I can explain further, but i just typed this on a cellphone, my fingers and eyes are spent.

[miketuite]

cgtech,

You have my undying respect for being able to compose a treatise on electric motors on a cell phone. I can barely text a sentence. I appreciate your effort.

The only question I have is, in layman's terms, what practical advantages does sepex offer vs. series? The answer may be in what you've written, but it isn't obvious to this electricity-impaired cart owner.

Thanks,

Mike

[cgtech]

First SERIES MOTORS

-Pros- best torque options. Easiest speed upgrades with stock controller, top speed generally limited by motor . Slightly cheaper motor controllers. Better chance of motor controller surviving a motor failure. Higher amp controllers available (more torque). IMO more robust for offroad/HD use.

-cons- No regenerative braking/putting energy back into batteries. No anti-rollaway feature. Requires more parts to facilitate forward and reverse.

SEPEX MOTORS

-pros- regen & anti-rollaway features. Less parts, forward and reverse handled by motor controller. Extra speed and torque is usually only a controller swap away. Most stock systems will try to keep you from over-revving motor (alltrax doesnt).

-cons- when motor fails, almost always kills controller too. Factory controller is usually a bottleneck for speed upgrades.

Swapping a sepex system to a series system (or vise-versa) is always expensive, sepex motors are only compatible with sepex controllers (same for series motors & controllers).

This is a pretty short list, Im sure there will be more pros/cons added by other users, im welcome to any additions.

[miketuite]

Thanks, cgtech. I really appreciate the benefit of your experience.

Mike