RoboteQ AX2550/2850 user manual Temperature-Based Current Limitation

Temperature-Based Current Limitation

You can select one of 7 current limit settings based on your robot’s component capabilities (motors, battery, wiring), up to the controller’s own limit. The available current limit values are shown in the table below.

TABLE 7. Continuous vs. Extended Amp limits table

Setting	Continuous High Amps	Extended Safe Amps
0	30A	30A
1	45A	45A
2	60A	60A
3	75A	75A
4	90A	80A
5	105A	80A
6	120A	80A

The controller will assume that any consumption above the safe continuous amps value will cause more heat to be generated than can be safely dissipated. The controller will keep an internal total of the estimated heat balance and will begin gradually reducing the output power when a maximum threshold has been reached. The higher the current is over the Continuous Safe Amps limit, the quicker it will reach the maximum threshold.

In practice, assuming the maximum Amps limit setting (120A), this means that the control- ler will allow up to 1 minute of operation at 100A or 15 seconds at 120A. When the control- ler runs below the Continuous Safe Amps limit, the controller will assume that it is cooling off and will allow for higher amp consumption at a later time. In practical robot maneuver- ing situations where stop and go is very common, the controller will be capable of deliver- ing the maximum Momentary High Amps whenever it is needed.

Temperature-Based Current Limitation

The AX2500/2850 also features active current limitation with a SmartAmps control algo- rithm. On the AX2500/2850, this current limiting is based on the actual measured tempera- ture of the heat sink, near the mounting point of the Power MOSFET transistors inside the controller. While the temperature is below 60oC, the controller will deliver up to 120A Con- tinuous Amps. For every degree of temperature rise above that threshold value, the limit is reduced from this absolute maximum amount. Furthermore you can select one of 7 cur- rent limit settings based on your robot’s component capabilities (motors, battery, wiring), up to the controller’s own limit. The current limit that is applied at any given time is the lesser value of your selected value, the computed limit using the SmartAmps algorithm and the maximum Amps the controller is allowed to deliver at its current temperature point. This capability ensures that the controller will be able to work safely with practically all motor types and will adjust itself automatically for the various load and environmental conditions. The time it takes for the heat sink’s temperature to rise depends on the current output, ambient temperature, and available air flow (natural or forced).

Note that the measured temperature is on the inside of the heat sink and will rise and fall faster than the outside surface.

AX2500/2850 Motor Controller User’s Manual 39