2.9 Control Structures2.9.1 Control PrincipleA frequency converter rectifies AC voltage from mains into DC voltage, after which this DC voltage is converted into ACpower with a variable amplitude and frequency.The motor is supplied with variable voltage/current and frequency, which enables infinitely variable speed control of three-phased, standard AC motors and permanent magnet synchronous motors.130BC514.123-phasepowerinputDC busMotorBrakeresistor88 (-)89 (+)95 PE93 (T/L3)92 (S/L2)91 (R/L1)(R-) 81(R+) 82(PE) 99(U/T1) 96(V/T2) 97(W/T3) 98Illustration 2.7 Control PrincipleThe control terminals provide for wiring feedback, reference, and other input signals to the following:• frequency converter• output of frequency converter status and fault conditions• relays to operate auxiliary equipment• serial communication interfaceControl terminals are programmable for various functions by selecting parameter options described in the main or quickmenus. Most control wiring is customer supplied unless factory ordered. A 24 V DC power supply is also provided for usewith the frequency converter control inputs and outputs.Table 2.7 describes the functions of the control terminals. Many of these terminals have multiple functions determined byparameter settings. Some options provide more terminals. See chapter 5.1 Mechanical Installation for terminal locations.Introduction Design Guide18 Danfoss A/S © Rev. 06/2014 All rights reserved. MG20Z20222
