User Manual
Chapter 2 - Introduction 11
Chapter 2 - General Description
DVS digital drives are designed to control the speed of three phase electric motors. They can control motors with a power
range from 0.25 kW to 0.75 kW (220 - 240 V) and from 0.35 HP up to 1 HP (220 V).
The drive rectifies the voltage of the mains power supply to obtain an intermediate circuit voltage, then uses an inverter bridge
applying sinusoidal PWM modulation to generate a three phase power supply with variable voltage and frequency permitting
regular, smooth motor control even at very low speeds.
Feed voltages to the various control cards are obtained from a switching power supply that also draws its power from the
intermediate circuit.
The inverter bridge is based on IGBT (Insulated Gate Bipolar Transistor) devices. Output is protected against short circuits
between the phases and to ground. If more than one motor is driven in parallel by a single drive (obviously of adequate power)
motors can be switched in and out independently even during normal drive functioning (see section 5.2.3).
If the motors used are not specifically designed for inverter control, a drop in output current of around 5 - 10% must be
allowed for. If nominal torque is demanded from such a motor at low speeds, an auxiliary motor cooling fan will be necessary
to dissipate the heat generated. If the necessary cooling assistance cannot be provided, then the motors will have to be over-
sized. In either case the user should contact the technical service of the motor manufacturer for further information.
If a motor has to function at a frequency greater than its nominal frequency, the user should again contact the manufacturers
technical service to ascertain what mechanical problems (bearing wear, balancing problems, etc.) could be incurred.
DVS drives can be controlled in a number of ways:
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via their control terminals
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using the control keys and display
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over an RS 485 serial line
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using a standard PC control program
Note!
The electronic control circuit terminals are electrically separate from the power circuit terminals, but the
control microprocessor is linked to the potential of the DC stage.
