RoboteQ AX2550, AX1500 user manual Overvoltage Protection, Undervoltage Protection

Connecting Power and Motors to the Controller

Please download the Application Note “Understanding Regeneration” from the

www.roboteq.com for an in-depth discussion of this complex but important topic.

Important Warning

Use the AX1500 only with a rechargeable battery as supply to the Motor Power wires (VMot terminals). If a transformer or power supply is used, damage to the con- troller and/or power supply may occur during regeneration. See “Using the Control- ler with a Power Supply” on page 36 for details.

Important Warning

Avoid switching Off or cutting open the main power cables (VMot terminals) while the motors are spinning. Damage to the controller may occur.

Overvoltage Protection

The AX1500 includes a battery voltage monitoring circuit that will cause the output transis- tors to be turned Off if the main battery voltage rises above 43V.

This protection is designed to prevent the voltage created by the motors during regenera- tion to be “amplified” to unsafe levels by the switching circuit.

The controller will resume normal operation when the measured voltage drops below 43V.

Undervoltage Protection

In order to ensure that the power MOSFET transistors are switched properly, the AX1500 monitors the internal 12V power supply that is used by the MOSFET drivers. If the internal voltage drops below 10V, the controller’s output stage is turned Off. The rest of the control- ler’s electronics, including the microcomputer, will remain operational as long as the inter- nal voltage is above 8V.

The internal voltage will be the output of the DC/DC converter which will be a solid 12V as long as either of the main battery or backup voltage is higher than 12.5V. If the main and backup voltage drop below 12.V, the DC/DC converter’s output will be approximately 0.5V lower than the highest input.

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 35, 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:

36 AX1500 Motor Controller User’s Manual Version 1.9b. June 1, 2007