Structure of NCT drive systems

Servo amplifiers of NCT drive system do not contain rectifier unit, each servo amplifier supplied by a separated power supply module. The power supply units and servo amplifier units connected via DC bus. The depths of the different modules are the same and all electric connectors are placed on the front panel, thus can be placed in one row and an aesthetic, clear, cable-friendly system can be generated. The order of the modules is optional, they can even be placed in several rows. The direct line supply and the modular construction characteristic to NCT drive systems make easier the electric planning, the implementation of line supply as well as the possible future enhancement or module replacement simple.

NCT Power Supply Units (DPS, DPB)

The most important task of NCT power supply units is to supply the servo amplifiers with energy. The servo amplifier inputs demand DC voltage that may only alter slightly in function of the loading. The rectified voltage of the three-phase line is directly connected to the DC bus output of NCT power supply units; the rippled rectified voltage is almost entirely smoothened by the capacitor battery on the DC bus. The line voltage and the line choke voltage basically determine the voltage of the DC bus. The task of the line choke is to decrease the harmonic content of the current absorbed or recuperated from the line. The line choke of DPB power supply units is a separated unit because of its big size. The NCT power supply units include a soft start system switching on and off in function of the DC bus voltage and charge the large-scale capacitor battery. The voltages of switch-on and switch-off differ. Provided the bus voltage is less than half of the nominal value, the soft start switches on, if however the bus voltage rises above 80% of the nominal value, the soft start switches off. Without soft start the overcurrent protection in front of the supply unit would immediately detach upon power-on. There is an operation mode (brake mode) in all drive systems, when the power flows from the motor to the main supply unit. The power supply unit transforms this power into heat on braking resistors or the recuperative unit charge back to power supply. There is no braking resistor in standard DPS power supply unit, so it does not heat the power supply unit and also the electric cabinet. Power supplies can be mounted with internal brake resistors as an option. Calculating the external braking resistor has to be done very carefully. Recuperative power supply is recommended in case of frequent braking even for the small power supplies. DPB power supply units force the power occurring upon brake back to the three-phase line.