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Connecting Power and Motors to the Controller
30 AX2500/2850 Motor Controller User’s Manual Version 1.7. February 1, 2005
Make sure that your motors have their wires isolated from the motor casing. Some
motors, particularly automotive parts, use only one wire, with the other connected
to the motor’s frame.
If you are using such a motor, make sure that it is mounted on isolators and that its
casing will not cause a short circuit with other motors and circuits which may also
be inadvertently connected to the same metal chassis.
Power Fuses
For low Amperage applications (below 30A per motor), it is recommended that a fuse be
inserted in series with the main battery circuit as shown in the Figure 11 above.
The fuse will be shared by the two output stages and therefore must be placed before the
Y connection to the two power wires.
Automotive fuses are generally slow and the following values are recommended depend-
ing on the desired level of protection. It should be noted that the current values listed will
apply to the sum of the current drawn by each channel. Practically, a fuse will be of limited
effectiveness. In very high current application (80A or more per channel), it will simply not
be possible to find a fuse with the necessary Amps rating and speed needed to provide
adequate protection. In such situation, the fuse may be just as well omitted keeping in
mind that the controller’s current limiting circuit may not be able to protect it against short
circuits and other abnormal situations.
Important Warning
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 AX2500/2850 regulates the output power by switching the power to the motors On
and Off at high frequencies. At such frequencies, the wires’ inductance produces undesir-
able effects such as parasitic RF emissions, ringing and overvoltage peaks. The controller
TABLE 5. Fuse selection table
Desired Current Protection (total for
Channel 1 + Channel 2) Fuse
120A 100A
100A 80A
80A 60A
60A 50A
50A 40A
40A 35A