Topology
The operating principle of the SD750 is the pulse width modulation (PWM). Varying the power supply
voltage and the grid frequency, it is possible to control the speed and torque of the connected induction
three-phase motors thanks to its main components: rectifier bridge, the DC bus, inverter bridge, and
power and control card.
General Block Scheme for frames 5 to 11
The SD750 drive is equipped with an input filter. This input filter significantly reduces the THDi values
and increases line impedance, thus protecting the drive from electrical system distortions. Depending on
the frame, the input filter is connected to the input or to the DC bus. From frames 3 to 11 the filter is
installed in the input side. In frames 1 and 2 the filter is installed on the DC bus (see figure “Power
electronics for Frames 1 and 2 equipment”).
Frames 5 to 11 integrate as standard ultra fast fuses that protect the drive against downstream
overcurrents. Additionally, the drive integrates multiple electrical protections that protect the drive and
the motor, similar to those provided by a motor protection relay.
The SD750 drive includes a power and a control board that are responsible for the rectifier bridge trip,
inverter bridge trip, soft load management, DC bus voltage control and motor operation. In addition, the
control card integrates terminals such as communication ports, digital and analogue inputs and outputs,
colour touch-screen display, alphanumeric display, etc.
The inverter bridge generates the PWM wave that controls the motor response (voltage, current, torque,
etc.). The Power Electronics SD750 series integrates as standard dV/dt filters and a CLAMP system that
reduces significantly the rise time (dV/dt) below 500V/μs - 800V/μs, therefore, it reduces the voltage
peaks in the motor windings, the common mode currents and the EMC emissions.
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