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I have a choice between the following two set-ups for a project. Option One is to have the motor controller mounted close to the batteries but further away from the motor. Option Two is to have the motor controller mounted closer to the motor but further away from the batteries.

I am wanting to know if there is any specific advantage in connecting everything in either Option One or Option Two in regards to cable losses? (Is it better to have the controller closer to the motor or is it better to have the controller closer to the batteries?).

I understand that there will be several factors which will affect the losses within the cables in either option such as cable length, cable gauge, temperature etc.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Good question but what about EMC ?I suspect that where currents are high option 1 would make less noise .If your DC motor controller is a buck convertor which is most likely there wont be much in it when it comes to losses because the buck convertor takes big peak currents. \$\endgroup\$
    – Autistic
    Oct 1, 2016 at 6:04
  • \$\begingroup\$ The controller is an H-bridge type and uses PWM (~15.4kHz) to drive the motor. The motor draws 18A on full load. My thinking is that there is not much difference between the two options. \$\endgroup\$
    – GrapeApe
    Oct 1, 2016 at 10:31

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Choose longer path with lower current; shorter path with higher current.

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  • \$\begingroup\$ I2R losses can be DC or AC. On high frequency using multiple small diameter conductors will reduce I2R losses (filtering will reduce frequency). \$\endgroup\$ Oct 1, 2016 at 6:52
  • \$\begingroup\$ @Anonymous I agree with your statement but if I use option two the controller is closer to the motor which means less losses between the controller and the motor, however this also increases the distance between the controller and the batteries which means longer cable between the controller and the batteries and therefore more losses. With option one you have a similar problem only this time there are more losses between the controller and the motor. \$\endgroup\$
    – GrapeApe
    Oct 1, 2016 at 10:39
  • \$\begingroup\$ Higher currents assume more "losses" in wires. Also putting controller closer to the motor will minimize EMI done by the motor's power lines, given proper EMI design of the motor controller. \$\endgroup\$
    – Anonymous
    Oct 1, 2016 at 10:45
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Consider choke between DC and controller with cap on input.

Use twisted pair short wires with ferrite torroid around all output wires to motor for PWM pulses to reduce CM noise and same to supply.

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  • \$\begingroup\$ Yes tony if you choke and cap then option 2 looks good .but what if the power is very high meaning big expensive choke and high ripple current caps ? \$\endgroup\$
    – Autistic
    Oct 1, 2016 at 6:11
  • \$\begingroup\$ better choices need detailed specs on load, spectrum, immunity, budget, quantity \$\endgroup\$ Oct 1, 2016 at 10:11

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