Control circuit arrangement for DC motors

A method of providing constant tension on a strip of material being wound on or unwound from a coil of material driven by the armature of a DC motor, the method comprising the steps of

• supplying the armature with electrical power,
• measuring a physical characteristic of the material being wound or unwound,
• utilizing this measurement to establish a predetermined level of current flow in the circuit of the armature,
• continuously measuring the voltage across the armature of the motor, continuously measuring the rate of travel of material being wound or unwound, and developing from the combination thereof a counter voltage for the field of the motor that functions to offset changes in the voltage of the armature,
• continuously directing said counter voltage to the field, and
• increasing the current in the armature by an amount corresponding to the reduction of armature voltage when the speed of rotation of the armature is decreased to the extent that the field of the motor becomes saturated, the increase in armature current being effective to maintain the power output of the motor constant, and thus provide constant tension on the strip of material being wound or unwound from the coil driven by the motor.