PowerPlus™ Power Supplies for ESPs

PowerPlus with Splitter Switch Powering Two Cells
  • PowerPlus™ Power Supplies for Electrostatic Precipitators

     NWL is the leading manufacturer of high voltage/high frequency switch mode technology power supplies for use in powering electrostatic precipitators (ESPs). PowerPlus™ units integrate the controller, the current limiting element and the T/R set functions into one compact high voltage power supply for use on the ESP.

    PowerPlus™ Models

    NWL offers the following PowerPlus™ models shown by kV rating:

    • 70kV – used with 300mm plate spacing
    • 83kV – used with 400mm plate spacing
    • 100kV – used with 500mm plate spacing

    PowerPlus Design Features

    Carrying on the tradition of supplying the most advanced power supplies for electrostatic precipitators, NWL began design and manufacturing of the PowerPlus™ in 2000. The use of Insulated Gate Bipolar Transistors (IGBT) provides for a power supply design that operates at a much higher frequency when compared to the operating frequency of a conventional single phase unit.

    NWL’s unique integrated design, places the power supply and control system on a common assembly. The system is packaged in a NEMA 4 (IP56) rated design for outdoor installations. NWL also has a complete line of mechanical switch designs to facilitate retrofit or new installations. NWL’s PowerPlus™ is configured utilizing the following functional blocks:

    PowerPlus Functional Block diagram

    PowerPlus Benefits

    The NWL PowerPlus™ has been installed on precipitators in many different industries and applications throughout the world. This product has proven to provide the following benefits to its users:

    • Increased collection efficiency
    • Decreased kVA for the same amount of power applied to the field
    • Faster spark response with less wasted spark current
    • Higher Reliability
    • Significantly higher power factor when compared to a conventional TR
    • Lower initial installation cost
    • Reduced space requirement with integrated design
    • Able to facilitate buss and guard or cable for HV connection

    The PowerPlus™ Design Process – Built on Proven Technologies, With Enhanced Ruggedness and Better Cooling

    In 2000 when NWL entered the switch mode power supply market, there was a design decision to be made – make the smallest and lightest power supply solution or design a unit that is positioned to deal with arcing loads installed in often hot and dirty locations. NWL’s design team chose the latter and as a result came to market with a switch mode power supply (PowerPlus™) that provides:

    1. A series resonant topology and control mode that turns the power supply into a current source that does not rely solely on the electronics acting quickly to limit the current, but, that the circuit itself, under shorted conditions, is inherently current limiting.
    2. A cooling system that does not require air filters and minimizes plant maintenance. The heat sink fin spacing is such that the IGBT cooling is not degraded as dust and dirt cannot accumulate and “clog” the fins; no air enters the control box, it is completely sealed.
    3. A power supply that is manufactured using proven methods previously used in conventional T/R sets. The result a unit that provides the lowest total cost of ownership and integrates with existing infrastructure.

    During the first several years of production, NWL put this new switch mode technology into the industries’ toughest environments. NWL then worked with users to continuously to improve the reliability of the product to obtain the high level of reliability that exists on the product being shipped today.

    Today’s NWL PowerPlus™ unit has a design that more closely resembles a conventional transformer rectifier than the other switch mode units in the market. The rugged design approach detailed in the three points above has been field validated as the necessary formula for a power supply that is rugged and reliable in the environment of an ESP roof top.

  • PowerPlus Ratings Table

    Country-Voltage KV Individual MA Unit Models Temperature Certifications
    380 83 675 / 1110 / 1540 / 1930 40°C Contact NWL
    380 100 920 / 1280/ 1600 40°C Contact NWL
    400 70 400 / 645 / 800 / 1200 / 1370 / 1830 / 2285 / 2860 40°C Contact NWL
    400 83 335 / 540 / 675 / 1010 / 1155 / 1540 / 1930 / 2410 40°C Contact NWL
    400 100 840 / 960 / 1280 / 1600 / 2000 40°C Contact NWL
    415 70 1430 / 1975 / 2460 50°C Contact NWL
    415 83 1205 / 1665 / 2075 50°C Contact NWL
    480 70 400 / 500 / 800 / 1000 / 1500 / 1715 / 2285 / 2860 40°C Contact NWL
    480 83 335 / 420 / 675 / 840 / 1265 / 1445 / 1930 / 2410 40°C Contact NWL
    480 100 1050 / 1200 / 1600 / 2000 40°C Contact NWL
    400-480 70 60 / 120 / 245 / 300 40°C Contact NWL
    400-480 83 50 / 100 / 205 / 255 40°C Contact NWL

    PowerPlusTM General Specifications — All Models

    Power Supply Standards Contact NWL
    Optional CE Certification Includes


    EMC Directive (2004/108/CE), Machinery Directive (2006/42/EC), EN 61000-6-4, EN 55011, EN 61000-6-2, EN 60204-1, EN ISO 12100-1, IEC 61000-4-2, IEC 61000-4-3, IEC 61000-4-4, IEC 61000-4-5, IEC 61000-4-6 , IEC 60204-1
    Enclosure Environmental Rating IP56, NEMA4
    Circuit Breaker IAC Rating
    @ 480VAC (UL & IEC rated)
    Power Factor 0.94
    % Ripple – KVp-p 3-5
    Resonant Frequency – KHz 50
    Arc Shutdown Time – μsec 30
    Minimum Ambient Temperature -20 °C
    Maximum Avg. Ambient Temperature (24 hr) 40 °C
    Maximum Ambient Temperature 50 °C (for up to 4 hours)
    Maximum Oil Temperature Rise 40 °C
    Maximum Tank Surface Temperature 75 °C
    Maximum Relative Humidity 100%
    Maximum Permissible Altitude 1000 m (3300 ft)
    Nameplate Material Aluminum 0.32” (8 mm) thick, satin finish
    Paint (primer) High solid alkyd primer, VOC compliant, gray, 1-1.5 mils (25-40μm)
    Paint (top coat) High build acrylic enamel, semi-gloss, 1-1.5 mils (25-40μ)
    Paint (color) ASA 61 gray (RAL 7042)
    Oil Level Switch Ratings 20VA contacts
    Minimum Ground Wire size #2 AWG Cu. per NEC, section 250 (35 mm2 Cu.)
    Input Connection Stabs for 5/16” – 3/8” ring lugs (8-10 mm), 1⁄2” ring lugs for 120 kW/100 kV units
    Output Termination 1⁄2” NPT Female on HV bushing
    External Safety Ground Termination 3⁄83⁄8-16 UNCF, (9.5 mm)
    Internal Neutral Ground Termination 3⁄8-16 x 1” stud, (10 mm)
    Low Voltage feed thru 1⁄4-20 UNCF epoxy feed thru, (7 mm)
    Windings Conductor Material Copper wire
    Insulation Class A
    Dielectric type Cross Grade 206 Mineral Oil (or equivalent) or Dow Corning 561 Silicone Fluid

    Paint Specifications

    There are three finish options for PowerPlus™ – one acrylic enamel paint and two powder coating finishes . The standard paint finish is VOC compliant, high-build acrylic enamel, suitable for most ambient conditions, that includes primer, top coat and color coat:·

    • Paint Primer: High solid alkyd primer, VOC compliant, gray, 1-1.5 mils (25-40μm)
    • Paint Top Coat: High build acrylic enamel, semi-gloss, 1-1.5 mils (25-40μ)
    • Paint Color: ASA 61 gray (RAL 7042)

    See detailed paint specifications (PDF) for more information about acrylic enamel finishes.

    For more challenging environmental conditions such as exposure to salt water and offshore installations, NWL also offers a powder coat rated for extreme corrosion resistance. View info on NWL Optional Powder Coat System (PDF).

    Grounding Specifications

    With over 1200 PowerPlus™ units in service, NWL has learned a many ‘best practices’ with respect to installation, operation, and maintenance.  A very important feature to greatly ensure trouble-free operation is to follow the grounding procedures as shown in the PowerPlus™ manual.  The following three grounding paths must be in place to ensure proper operation:

    1. Electrostatic Precipitator (ESP) Grounding: The precipitator collecting plates must be securely grounded to the frame of the ESP box.  All sections of the box itself must be tied to the plant ground grid.  This must be the same ground grid used for the incoming PowerPlus power source.  It has been NWL’s experience that if the power source ground grid is not the same as the ESP ground grid, IGBT failures may occur during sparking or arcing conditions.
    2. Low Impedance Return Path: Since the output current of the PowerPlus™ unit is much greater than a conventional T/R set (50 kHz to 120 Hz), it is important to have a low impedance path (at 50kHz) from the collecting plates (inside the ESP box) to the PowerPlus™ HV tank ground.  To get this low impedance, the HV ductwork should be kept as short as possible, and all flange connections must be jumpered with at least two pieces of copper braid to guarantee a good connection through the joints.  Because this is such a critical area, a redundant path is required using #6 AWG copper (minimum).  This copper wire must be solidly grounded where the HV ductwork enters the ESP.  The wire must then run alongside the ductwork (also known as pipe and guard) and terminated at the ground boss located directly on the HV tank.  It has been NWL’s experience that not installing this ground return wire may cause premature failure of the IGBT’s under sparking or arcing conditions within the ESP.
    3. PowerPlus Grounding: Many ESP boxes have a heavy copper wire (» 1/0 AWG or larger) that runs around the perimeter of the ESP roof, drops down along the side, and ties to the plant ground grid underneath the ESP.  To minimize problems due to voltage and arcing transients, it is advisable to securely tie the frame of each PowerPlus unit to this heavy ground wire that runs around the perimeter of the ESP.  Each unit should be tied to this ground using a cable sufficiently sized per NEC.  The ground wiring must not be “daisy-chained” from one unit to the next unit.  Each unit must be individually routed to this ground.

    It is strongly recommended that any installed PowerPlus units be check to make sure they are properly grounded as shown in this drawing (PDF).  It may avoid premature problems with the units.  Please remember, failures caused by improper grounding are not covered under the NWL original equipment warranty as stated in the PowerPlus™ manual (available in the client login area).