Motor Brush questions Testing PDS SEPEX

[pecothern]

My motor failed its a PDS SEPEX motor Once inside the motor I found a brush melted and falling apart.. I replaced the brushes but now when I test the motor I hook A1 and F1 to negative 12 volts and A2 and F2 to positive 12 volts the motor runs in reverse. If I switch the field F1 F2 the motor runs forward Did I put the brushes in incorrectly? I thought it should run forward hooked up A1 F1 to neg and A2 F2 hooked to positive can anyone confirm ? Thanks for your time and knowledge.

[JohnnieB]

Originally Posted by pecothern

My motor failed its a PDS SEPEX motor Once inside the motor I found a brush melted and falling apart.. I replaced the brushes but now when I test the motor I hook A1 and F1 to negative 12 volts and A2 and F2 to positive 12 volts the motor runs in reverse. If I switch the field F1 F2 the motor runs forward Did I put the brushes in incorrectly? I thought it should run forward hooked up A1 F1 to neg and A2 F2 hooked to positive can anyone confirm ? Thanks for your time and knowledge.

The motor shaft turns CW when A1 and F1 are connected to one polarity and A2 and F2 connected to the other. Whether that moves the cart forward or backwards depended on the how many gears interfaces between the motor shaft and the tires.

Typically, if armature and field currents are in-phase the motor shaft turns CW and when they are out of phase, the shaft turns CCW. However, some motors are wired differently and the opposite is true.


What it boils down to, if the cart direction doesn't match the direction selector, swap the F1 and F2 lead.

[pecothern]

Ok that helps a lot thank you I have a question when I first hooked up my rebuilt controller. The cart was going forward slowly with reverse selected and buzzer buzzing then fast in reverse when forward was selected on the dash switch. I switched the A1 and A2 wires at the motor. Instead of the F1 F2 wires. Would that damage the controller.?, Now I put it back A1 and A2 correctly and switched the F1 F2 wires and it will go forward only. In reverse the solenoid clicks in but then seems to release and no movement the controller did seem to get very hot under the A1 spade when I had the motor reverse A1 A2

The reason I ask is I'm worried I put the brushes in wrong and have inadvertently put the stud for A2 in the A1 position and vice versa is that even possible.? I put the brush in and put the stud in the closest hole and put the other one 180 degrees and same for the other set. Does it matter?? the A's and F's are same or opposite polarity for forward and backwards. For instance could you switch the A's instead of F's to change direction?

[JohnnieB]

It doesn't much matter which is A1 or A2 as long as one is connected to Battery B+ and the other to the controller's M- terminal, which is labeled A1 on a PDS controller.

Swapping A1 and A2 to change direction motor rotates doesn't hurt anything either.

When direction selector is in R, the beeper beeps and the controller is placed in half-speed mode, so you want to swap the cables until the cart direction matches the direction selector.

[pecothern]

Fantastic. Thank you so much for confirming my hunch.

[kantuckian]

Thanks

[pecothern]

I'm putting this here to continue the thread till completion to answer questions and help someone in the future ..

Ive done some more testing this morning This controller is putting power 10-12 volts to the fields when in forward but nothing to the fields when in reverse. I understand it is suppose to reverse polarity to the field for reverse. The switch on the dash test good and the buzzer is sounding in reverse so the controller knows it is suppose to be in reverse. the fields measure 1.5 ohms I cant find any skinned wires along the field wires . I believe the controller is defective though I just had it rebuilt. The previous controller was damaged when one of the brushes overheated and crumbled allowing a wire to touch the motor housing. As stated earlier I put new brushes in the motor and cleaned it up good and it runs forward when connecting it to 12 volts armature and field same polarity and it runs reverse when i switch the polarity on the fields

Several Questions for JohnnieB I understand direction is determined by field polarity.. does the controller control the speed purely by modulating voltage up and down to the fields.? Would I expect lower voltage on the field when it is reversed so speed is decreased? Is the Armature simply ON/OFF? switched mainly by the solenoid? I noticed when up on jacks the solenoid stays on even when releasing the pedal as the wheels coast down to a stop, is that the regenerative kicking in to charge the batteries ?

[JohnnieB]

You have a SepEx (Separately Excited) drive, which means the field windings are powered (excited) from a separate power source than the armature. Which in turn means the PDS controller is actually two controllers in one box. The armature is fed by a high power controller while the field is powered by a low power one, about 1/10 the output of the high power one.

The output of both is PWM (Pulse Width Modulated) DC. The MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) that pass the power are either turned on or turned off and they switch states at about 18,000 time per second. When on, the MOSFETs pass whatever the battery pack voltage is at the time to whatever they are connected to and when off, the output is 0V.

The power being passed is regulated by the duty cycle of the PWM pulses, so the effective (average) voltage applied to what the MOSFETs are connected to varies from 0% to 100% of the pack voltage for the high power controller and from 0% to about 10% for the low power controller.

The low power controller is also bipolar so the direction the motor rotates can be changed. Attached is a drawing of a generic sepex controller using an H-Bridge to change field polarity, plus two more with voltage paths highlighted for forward and reverse.

The field excitation does not control the motor's speed, it controls the motor's speed/torque curve. When more power is applied to the field, low end torque increases and when less power is applied to the field, high end torque increases. In other words, the same motor can produce good acceleration from a standstill like a torque wound series drive motor and good high speed performance like a speed wound series motor just by adjusting the number of amps flowing through the field windings. The process is called field mapping.

The low power controller also regulates the amount of regen braking.

The solenoid is controlled by the controller and it is turned on and off by things other than the pedal switch alone, so it neither closes or opens in sync with the pedal.

Hope this clarifies more than confuses.

[pecothern]

Thanks JohnnieB I understood about 90%. Thanks for taking the time. Looks like my "rebuilt" controller is having problems. I sent it back for them to take another look at it. If it was my cart I'd upgrade to Alltrax but trying to fix it cheap as possible for my aunt's grown special needs son.

[pecothern]

Question about this DC motor. I sent this controller in to be rebuilt. I tested the motor by putting 12 volts on the field and a1 a2. Motor would not move. I disassembled the motor and found 2 of the brushes worn way down to the point one of the wires were touching the frame of the motor. I cant remember which two brushes were worn down to nubs but they were on the same pole a1 or a2. I cleaned the motors sanded the armature lightly and replaced the brushes. When i hooked up my rebuilt controller nothing happened till i pushed the wheel to get things moving then things started working except it would only spin in reverse, with wheels off the ground. forward nothing happens I tested the field contacts on the controller and it was doing nothing in forward. so I sent the controller back for them to check it. Now when I test the motor with 12 volts with jumper cables the motor does spin forward and backward when i reverse the fields "wheels always off the ground" but man the jumper cable get really hot. IDK seems like the motor is pulling a lot of power. Also can I run it awhile like that to allow the brushes to "wear" to the armature? Did those brushes not fitting the armature well cause the rebuilt controller to fail immediately?