VSD Peripherals

VSD installations might require or benefit from the use of some additional peripherals depending on the application (e.g., heavy industrial use, large motors, motor types etc.) and environment (quality of power source, interference of/with other applications, distance between VSD and motor etc.) of the installation. These VSD Peripherals, typically include items such as the following:

  • DC Bus/Link Chokes/Reactors - Reactors for Power Factor Improvement
  • AC Chokes/Reactors (Input and Output) - Reactors for Harmonic Filtration
  • AC EMC/EMI Filters (Input and Output) - Filters for Noise Disturbance
  • Sine Wave Filters
  • Dynamic Braking Systems with:
    • Porcelain Braking Resistors/Windings; or
    • Aluminium Housed Braking Resistors
VSD Peripherals

Besides the abovementioned, even though VSDs include built-in Voltage Dependent Resistors (VDR) for suppressing surge voltage, the use of SPDs (Surge Protection Devices) are strongly recommended for all installations to protect the VSDs from frequent surges, large Eskom power surges as well as lightning (although SPDs only provide protection to some degree). This is typically important for warranty and insurance claims that might arise from damages caused by lightning or power surges. Further to this, although VSDs include a motor overload protection function, in circumstances where a single VSD is used to drive two or more motors, Thermal Motor Protection Relays (Thermal Overload Relays - LRDs) are also recommended to prevent motor over-heating (installed between the VSD and each motor). Also, if the rated capacity of the motor does not match that of the VSD (especially when the VSD’s rated power is greater than the motor's), it is advisable to adjust the motor protection parameters on the VSD, or to install a thermal relay in the motor circuit for protection.

DC Chokes (Reactors for Power Factor Improvement)

Installation of DC Bus/Link Chokes/Reactors are highly recommended for applications from 250kW and larger (possibly from 90kW depending on circumstances). These units are connected after the input diode in the VSD circuit (rectifier circuits) and are used to smooth the rectified current (improves the input current wave form distortion caused by the capacitor). This then:

  • reduces the rectifier damage
  • prevents capacitor overheating
  • increases the power factor
  • suppresses sudden changes in grid voltage (power supply)

TCGC offers the following DC Bus/Link Chokes/Reactors:

  • EM-RAD3 (3-Phase 380-460V) – From 0.4 kW up to 560 kW
  • EM-RAD5 (3-Phase 525-575V) – From 0.4 kW up to 560 kW

*Manufactured with Amp ratings according to specific requirement (Custom Voltage options also available on request).

*For installations where a DC Choke is required the VSD wiring needs to be reconfigured by the manufacturer.

DC Chokes

AC Chokes (Reactors for Harmonic Filtration)

The use of Line Reactors and Load Reactors increases the reliability, performance and efficiency of VSD systems and extends the life of both the VSDs and motors.

Input Chokes (Line Reactors)

Connected in series with the incoming power supply line and is recommended when the power supply is unbalanced or when power factor is poor in order to:

  • protect the VSD from transient overvoltage conditions typically caused by utility capacitor switching;
  • reduce the harmonic distortion and imbalance of the power supply current;
  • reduce over-voltage trips caused by transient voltage spikes and power line surges;
  • protect input rectifiers from in-rush current caused by sudden power supply surges and sags;
  • extend the life of the DC bus capacitor bank by reducing the internal heating caused by ripple currents.

Output Chokes (Load Reactors)

Used for operating ‘non-VSD duty’ motors or when the length of wiring between the VSD and motor exceeds 50 metres (can consider from 25 metres). This is to:

  • protect the motor insulation against VSD short circuits and IGBT reflective wave damage;
  • allow the motor to run cooler by ‘smoothing’ the motor current waveform;
  • reduce the effects of high motor wiring capacitance and ‘soften’ the dv/dt (high rates of change of voltage) applied to the motor windings;
  • suppress the capacitive charging current of the cable between the VSD and motor;
  • protect motor windings.

TCGC offers the following AC Chokes/Reactors:

  • Input Chokes (Line Reactors) – From 0.75 kW up to 600 kW
    • EM-RAI3 (3-Phase 380-450V)
    • EM-RAI5 (3-Phase 525-575V)
  • Output Chokes (Load Reactors) – From 0.75 kW up to 600 kW
    • EM-RAO3 (3-Phase 380-450V)
    • EM-RAO5 (3-Phase 525-575V)

*Manufactured with Amp ratings according to specific requirement (Custom Voltage options available on request).

AC Chokes

AC EMC/EMI Filters (For Noise Disturbance)

Some frequency-dependant electronic components can produce electric, magnetic or electromagnetic fields, which, if strong enough, can interfere with other appliances (cause undesired effects).  Electromagnetic Compatibility (EMC) is the ability of electrical equipment to operate without being affected by or causing Electromagnetic Interference (EMI).

Input Filters

Prevents EMI and radio interference which comes from the power supply cable to the VSD. To be installed when other appliances cause interference on the VSD supply line (power supply line).

Output Filters

Prevents EMI or radio interference which comes from the VSD cable to the motor. To be installed when there is interference on the VSD output line to the Motor (motor supply line).

TCGC offers the following AC EMC/EMI Filters for Noise Disturbance:

  • Input Filters – From 0.75 kW up to 560 kW
    • EM-FIT3 (3-Phase 380-450V)
    • EM-FIT5 (3-Phase 525-575V)
  • Output Filters – From 0.75 kW up to 560 kW
    • EM-FOT3 (3-Phase 380-450V)
    • EM-FOT5 (3-Phase 525-575V)

*Manufactured with Amp ratings according to specific requirement (Custom Voltage options available on request).

AC Filters

Sine Wave Filters

AC motors operate at their peak efficiency when they run on clean sinusoidal power. VSD’s produce square waves that are modulated so that the pulse width of the square waves can be varied continuously (known as pulse width modulation - PWM). VSDs maintain fine control over the width and amplitude of the square waves so that they take on the appearance (as viewed on an oscilloscope) of good approximations of a sine wave. Yet, even the most sophisticated VSD’s fail to match the purity of a true sine wave. Installing a sine wave filter between the VSD and the motor itself ‘smooths’ the VSDs PWM signal and converts it into a nearly perfect sinusoidal power wave form. This then:

  • reduces motor insulation stress and eliminates switching acoustic noise from the motor;
  • prevents disturbing pulses from being transmitted to the motor;
  • minimises eddy current losses in the motor, resulting in a cooler motor and thus extended motor lifetime;
  • reduces capacitances in screened motor supply cables which cause high oscillating circuit currents through motor bearings, vaporising lubricant, and causing damage to the bearings (especially in motors above 50 kW);
  • provides protection for the VSD (due to the lower pulse load being reflected in lower semiconductor losses).

To be installed for applications using older motors, applications in ‘aggressive’ environments, applications requiring frequent braking, 690V applications with general purpose motors and applications where cable lengths between the VSD and motor is 150 to 500 metres (can reach 3000 metres).

TCGC offers the following Sine Wave Filters:

  • EM-SWF3 (3-Phase 380-440V) – From 0.75 kW up to 630 kW
  • EM-SWF5 (3-Phase 525-575V) – From 0.75 kW up to 630 kW

*Manufactured with Amp ratings according to specific requirement (Custom Voltage options available on request).

Sine Wave Filter

Dynamic Braking Systems

Generally used for industrial applications where quick stopping is required which could cause the DC bus voltage to rise (over voltage). It is thus required where the regenerated energy needs to be dissipated quickly to manage the DC bus voltage to prevent the VSD from tripping.

Each system consists of a Brake Unit with Porcelain Windings. For the smaller systems, Aluminium Housed Braking Resistors can be used instead of the Porcelain Windings.

These systems are used for dissipative energy (cheap and simple method) by converting regenerative energy into thermal energy (burn off energy). Smaller VSDs include a built-in switch (IGBT) to divert extra power to a resistor - external units are thus only needed to burn off extra energy. If there is a large amount of regenerative energy or the VSD does not have a built-in braking switch, external braking systems could thus be required.

  • These systems can release the energy regenerated during motor speed regulation (via brake resistance) to produce enough braking torque to ensure normal operation of the transducer and other devices.
  • These systems are popular for use in cable/wire drawing machines, cranes, elevators, production machinery, mine hoists, centrifugal and oil pumps in oil field, etc.

TCGC offers the following Dynamic Braking Systems (listed according to VSD kW Range):

  • 0.75kW up to 22kW: EM-B U1 (single porcelain resistors ranging from 100W/500Ω to 3KW/30Ω)
  • 30kW up to 45kW: EM-B U2 (single porcelain resistors ranging from 5KW/20Ω to 10KW/8Ω)
  • 55kW up to 110kW: EM-B U3 (single or pair of porcelain resistors ranging from 10KW/8Ω to 12KW/6.8Ω)
  • 132kW up to 160kW: EM-B U3H (pair of porcelain resistors of 12KW/6.8Ω)
  • 185kW up to 220kW: EM-B U4H (pair or single cabinet of porcelain resistors ranging from 12KW/6.8Ω to 30KW/4Ω)
  • 250kW up to 315kW: EM-B U5H (single cabinet with porcelain resistors ranging from 40KW/3Ω to 40KW/3Ω)
  • 355kW up to 500kW: EM-B U4H (double cabinet with porcelain resistors ranging from 50KW/2.5Ω to 70KW/2Ω)

*Custom Watt/Ohm porcelain resistor options available on request.

Instead of the matched Porcelain Windings (brake resistors) used for the abovementioned Brake Units, Aluminium Housed Braking Resistors can also be used.

TCGC offers Aluminium Housed Braking Resistors for VSDs ranging from 0.75kW up to 15kW with resistors ranging from 100W / 500Ω to 3KW / 50Ω.

*Custom Watt/Ohm aluminium housed braking resistor options available on request.

Breaking Unit
Porcelain Winding Cabinet
Porcelain Winding Pair
Porcelain Winding - Single
Aluminium Resistor