Nidec Leroy-Somer Powerdrive MD Smart, Руководство по интеграции

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GENERAL INFORMATION
Powerdrive MD Smart Integration Guide
5751 en - 2021.10 / e
GENERAL
INFORMA
TION
The Nidec Leroy-Somer offer consists of:
Single rectifier chassis
The MD3REC1 single rectifier chassis is a mixed three-phase bridge assembly: 3 thyristors and
3 switching diodes. The 3 thyristors are only used to preload the DC BUS at start-up. After this
phase, the rectifier is used as a full voltage diode bridge. Each thyristor or diode connects one
of the 3 phases to one of the 2 terminals of the DC bus. The rectifier also incorporates a control
card to control the thyristors and make them a standalone DC power supply.
1.2.2.2 - Active rectifiers
An active rectifier allows the energy produced by driving machines or during rapid decelerations to be injected back into the network
(4 quadrants of the torque speed plane). They also limit the harmonic content to very low levels (THDI ≤3%).
This rectifier has an identical structure to an IGBT (Insulated Gate Bipolar Transistor) inverter, which is controlled by the MLI Pulse
Width Modulation method. It must be associated with a control module. In rectifier mode, it generates a regulated and adjustable
continuous voltage from the network power voltage.
In order to minimise the disturbance generated by the IGBT control and to guarantee a virtually sinusoidal input current (THDI)
<5%), a filtering system must be installed upstream of the rectifier.
Reminder: radio frequency (RFI) signal transmission
Variable speed drive inverters switch high voltages (> 550 V) at high frequencies (several kHz).
As a result, they generate radio frequency (R.F.) signals that can disrupt the operation of other devices:
• due to the high-frequency leakage currents that "leak" to the earth by the leakage capacity of the variator/motor cable and that of
the motor through the metal structures supporting the motor.
• via conduction or re-injection of R.F. signals on the power cable: conducted emissions
• by direct radiation in the vicinity of the power supply or variator/motor cable: radiated emissions.
The inverters are adapted to the EMC environments described in IEC/EN 61800-3 category C3. It is possible to add an optional
additional filter in the case of a more severe EMC environment.
The main advantages of such a reversible system are:
- possible return of energy to the power grid
- the input current waveform is slightly distorted, almost sinusoidal
- the power factor upstream of the converter is very close to 1
- the output voltage for the motor may be higher than that available on the AC power network. Because the voltage of the DC Bus
is regulated at a higher value than that of a passive rectifier, it is possible to obtain a motor voltage of 480 V. In some cases, if the
motor allows it, this function allows a lower motor current to be obtained and consequently the design of the output inverter to be
optimised.
Power network
AC
Single passive rectifier
MD3REC1