EMC Installation for Variable Speed Drive Systems (VSDs): Fields, Emissions, Coupling, and Shielding

Introduction

Today, alternating driving has become the system used in most modern industries, so the development of these systems has led to the emergence of driving systems operating at variable speeds to ensure the requirements of torque and speed (Armstrong, 2006; Armstrong, 2007; Alhelou et al., 2016).

The variable speed drive systems are used in industrial facilities for many purposes, the most important of which are energy saving, compatibility between driving speed and desired speed requirements, improving the life of electronic equipment as a result of smoothing start and increasing the life of mechanical equipment. Figure: 1 show the Basic elements of VSD power circuit.

Figure 1.

Basic elements of VSD power circuit

The variable-speed drive systems, like other equipment, are subject to EMC, then enters the phase of the smoothing, and finally returns to the alternating state by means of the different modulation techniques (PWM, SPWM, SVPWM, ... etc.).

The inverter consists of IGBT transistors or other electronic components with a on and off time between 50-200 ns at high values ​​for the desired voltage and currents (IEC TS 61000-1-2, 2008).

Usually the switching frequency is between 2-20 kHz. The inverter uses different electronic elements and sometimes they are controlled by different electron elements and microcontroller with up to 40 MHZ of on/off frequency (Steenstra et al., 2008; Williams et al., 2012).

Variable speed drive systems use large cooling fans for electronic equipment, which is considered to be a very sensitive VSD infrastructure which usually forms the basic structure of drive and is convenient low inductance base for EMC of cable screen, etc.

Harmonics generated by an individual drive are unlikely to cause interference, but they are cumulative so that an installation containing a high proportion of drive loads may cause difficulties (Fini et al., 2016; Alhelou et al., 2018; Zamani et al., 2018; Alhelou et al., 2015; Njenda et al., 2018; Haes Alhelou et al., 2018).

Apart from supply harmonics, emission also occurs as a result of the switching of the power output stage over a wide range of frequencies which are harmonics of the basic switching frequency – that is, size times the supply frequency for a 6-pulse DC drive, and the PWM carrier frequency for a PWM drive. This covers a range extending from 300Hz, for DC drives, up to many MHz for AC drives. Unwanted electromagnetic coupling is relatively unusual at frequencies below about 100kHz. Few standards set limits in that range, and interference problems are unusual.

The power stage of a variable speed drive is a potentially powerful source of electromagnetic emission (noise), because of the high voltage and current which is subject to rapid switching. The power output connections of a drive carry the highest level of high frequency voltage. They can be a powerful source of electromagnetic emission.