RoboteQ Using the Controller with a Power Supply, AX3500 Motor Controller User’s Manual

Using the Controller with a Power Supply

Using the Controller with a Power Supply

Using a transformer or a switching power supply is possible but requires special care, as the current will want to flow back from the motors to the power supply during regenera- tion. As discussed in “Power Regeneration Considerations” on page 37, if the supply is not able to absorb and dissipate regenerated current, the voltage will increase until the over- voltage protection circuit cuts off the motors. While this process should not be harmful to the controller, it may be to the power supply, unless one or more of the protective steps below is taken:

•Use a power supply that will not suffer damage in case a voltage is applied at its output that is higher than the transformer’s own output voltage. This information is seldom published in commercial power supplies, so it is not always possible to obtain positive reassurance that the supply will survive such a condition.

•Avoid deceleration that is quicker than the natural deceleration due to the friction in the motor assembly (motor, gears, load). Any deceleration that would be quicker than natural friction means that braking energy will need to be taken out of the sys- tem, causing a reverse current flow and voltage rise. See “Programmable Accelera- tion” on page 47.

•Place a battery in parallel with the power supply output. This will provide a reservoir into which regeneration current can flow. It will also be very helpful for delivering high current surges during motor acceleration, making it possible to use a lower current power supply. Batteries mounted in this way should be connected for the first time only while fully charged and should not be allowed to discharge. The power supply will be required to output unsafe amounts of current if connected directly to a discharged battery. Consider using a decoupling diode on the power supply’s output to prevent battery or regeneration current to flow back into the power supply.

•Place a resistive load in parallel with the power supply, with a circuit to enable that load during regeneration. This solution is more complex but will provide a safe path for the braking energy into a load designed to dissipate it. To prevent current from flowing from the power supply into the load during normal operation, an active switch would enable the load when the voltage rises above the nominal output of the power supply.

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