In an installation controlling the operation of one or more motors driving a mechanism for deploying or retracting a protective canopy over the cargo compartment of a truck or wagon, a method and device for protecting the motor windings against excessive power use by measuring the level of drawn current with a digital ammeter. If the current exceeds a threshold level of operation, a timer is started. As soon as a given absolute safe period of operation is surpassed, a breaker switch is tripped interrupting the motor power supply. A plural number of trip points can be programmed into the device.