Pulse width modulation (PWM)

The Beckhoff terminals and box modules integrate compact PWM output stages in the smallest of designs.

PWM output stages control the output current through pulse width modulation (PWM) of the supply voltage. This means that the full supply voltage is activated or deactivated at the output. The duty cycle (pulse width) is modified, but not the voltage level. The current is built up based on the load connected to the inductance.

Pulse width modulation (PWM) 1:
Operation at load with adequate inductance
Pulse width modulation (PWM) 2:
Operation at load with inadequate inductance (near ohmic)

The figure Operation at load with inadequate inductance (virtually ohmic) illustrates operation with an inadequate inductance. Continuous current flow is not reached. The current has "gaps". This mode of operation is not permitted.

Pulse width modulation (PWM) 3:

Pulse width current terminals require inductive loads

The load inductance should have a minimum inductance of 1 mH. Operation of the pulse width current terminals at loads with an inductance of less than 1 mH is not recommended, since the intermittent current flow prevents reference between the set value and the arithmetic mean of the current.