# Pulse Tightening with Direct Driven Electrical Tools

The principle below is applicable for direct driven electrical tools. It is applicable to the Atlas Copco SRB series of tools.

The pulse tightening uses a technique of pulsing the electrical current in the motor and has two distinct features:

- An action current that adds positive torque in the tightening direction.

- A reaction current that creates a comfort reaction by applying a reverse torque.

Pulse tightening principle

A | Action pulse to apply tightening force.
B | Reaction pulse for comfort

The figure shows the general principle of a current pulse tightening strategy. The detailed curve depends on the tool type and the tightening algorithm.

The pulse period consists of two phases as shown in the figure with an action current and a reaction current. Each action pulse adds torque to the tightening until the final target is reached. Each reaction pulse creates a counterforce that provides a comfortable reaction.

The energy level of the action phase and the reaction phase are configurable parameters. The combination of these two parameters creates an efficient tightening combined with operator comfort.