Data Sheet

Self Protection against Power Stage Failure

Advanced Digital Motor Controller User Manual 41

The controller must have the Power Control input wired to the battery so that it can oper-

ate and communicate independently of the power stage. The controller’s processor will

then activate the contactor coil through a digital output conﬁgured to turn on when the

“No MOSFET Failure” condition is true. The controller will automatically deactivate the coil

if the output is expected to be off and battery current is above 500mA to 2.5A (depending

on the controller model) for more than 0.5s.

The contactor must be rated high enough so that it can cut the full load current. For even

higher safety, additional precaution should be taken to prevent and to detect fused contac-

tor blades.

This contactor circuit will only detect and protect against damaged output stage condi-

tions. It will not protect against all other types of fault. Notice therefore, the presence of

an emergency switch in series with the contactor coil. This switch should be operated

manually or remotely, as discussed in the Manual Emergency Power Disconnect the Re-

mote Emergency Power Disconnect and the Protection using Supervisory Microcomputer

earlier in this section of the manual.

Using this contactor circuit, turning off the controller will normally deactivate the digital

output and this will cut the power to the controller’s output stage.

Important Warning

Fully autonomous and unsupervised systems cannot depend on electronics alone to

ensure absolute safety. While a number of techniques can be used to improve safety,

they will minimize but never totally eliminate risks. Such systems must be mechani-

cally designed so that no moving parts can ever cause harm in any circumstances.