User Manual

Connecting Power and Motors to the Controller
28 Advanced Digital Motor Controller User Manual V2.0, July 8, 2019
Important Warning
Avoid long connection between the controller and power source, as the added in-
ductance may cause damage to the controller when operating at high currents. Try
extending the motor wires instead since the added inductance is not harmful on
this side of the controller.
If the controller must be located at a long distance from the power source, the effects of
the wire inductance may be reduced by using one or more of the following techniques:
• Twisting the power and ground wires over the full length of the wires
• Use the vehicle’s metallic chassis for ground and run the positive wire along the
surface
• Add a capacitor (10,000uF or higher) near the controller
Electrical Noise Reduction Techniques
As discussed in the above section, the controller uses fast switching technology to control
the amount of power applied to the motors. While the controller incorporates several cir-
cuits to keep electrical noise to a minimum, additional techniques can be used to keep the
noise low when installing the controller in an application. Below is a list of techniques you
can try to keep noise emission low:
• Keep wires as short as possible
• Loop wires through ferrite cores
• Add snubber RC circuit at motor terminals
• Keep controller, wires, and battery enclosed in a metallic body
Battery Current vs. Motor Current
The controller limits the current that flows through the motors and not the battery cur-
rent. Current that flows through the motor is typically higher than the battery current. This
counter-intuitive phenomenon is due to the “flyback” current in the motor’s inductance. In
some cases, the motor current can be extremely high, causing heat and potentially dam-
age while battery current appears low or reasonable.
The motor’s power is controlled by varying the On/Off duty cycle of the battery voltage
16,000 times per second to the motor from 0% (motor off) to 100 (motor on). Because
of the inductive flyback effect, during the Off time current continues to flow at nearly
the same peak - and not the average - level as during the On time. At low PWM ratios,
the peak current - and therefore motor current - can be very high as shown in Figure 1-4,
on next page.
The relation between Battery Current and Motor current is given in the formula below:
Motor Current = Battery Current / PWM ratio