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AX500 Motor Controller User’s Manual 31
Wire Length Limits
Fuses are typically slow to blow and will thus allow temporary excess current to flow
through them for a time (the higher the excess current, the faster the fuse will blow).
This characteristic is desirable in most cases, as it will allow motors to draw surges
during acceleration and braking. However, it also means that the fuse may not be
able to protect the controller.
Wire Length Limits
The AX500 regulates the output power by switching the power to the motors On and Off at
high frequencies. At such frequencies, the wires’ inductance produces undesirable effects
such as parasitic RF emissions, ringing and overvoltage peaks. The controller has built-in
capacitors and voltage limiters that will reduce these effects. However, should the wire
inductance be increased, for example by extending the wire length, these effects will be
amplified beyond the controller’s capability to correct them. This is particularly the case for
the main battery power wires.
Important Warning
Avoid using long cable lengths (beyond 2 feet) from the main power battery to the
controller as the added inductance may cause damage to the controller when oper-
ating at high currents. Try extending the motor wires instead since the added induc-
tance is less harmful on this side of the controller.
If the controller must be located at a longer distance, 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 sur-
face
• Add a capacitor (5,000uF or higher) near the controller
Electrical Noise Reduction Techniques
As discussed in the above section, the AX500 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 AX500 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 R/C circuit at motor terminals
• Keep controller, wires and battery enclosed in metallic body
Power Regeneration Considerations
When a motor is spinning faster than it would normally at the applied voltage, such as
when moving downhill or decelerating, the motor acts like a generator. In such cases, the
current will flow in the opposite direction, back to the power source.