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HV ceramic resistors now available as axial-leaded and slab types.

PPM can now supply high voltage ceramic resistors in axial leaded and slab types, manufactured by specialist Swedish manufacturer Kanthal.  The 500BA ceramic slab resistors and BA100 & 200 axial-leaded ceramic resistors extend a high voltage ceramic portfolio already including tubular, disk/washer and water cooled resistors.

Kanthal bulk ceramic resistorsHigh peak power and high energy

Both the axial leaded and slab types provide excellent performance where high peak power or high-energy pulses must be handled in a small size. The bulk construction produces an inherently non-inductive resistor and allows energy and power to be uniformly distributed through the entire resistor body. Therefore, there is no film or wire to fail. Maximum continuous operating temperature of both types is specified at 230°C. The standard dielectric coating is recommended for use in air, and the oil-resistant coating is recommended for use in oil. Custom designs are also available.

  • Axial leaded resistors available with peak voltage of up to 25kV and resistance values from 2ohms to 7.5Mohm.
  • Slab resistors can support a peak voltage of up to 65kV and range in resistance from 1ohm to 1.8Mohm.

More information on each range can be found on the ceramic resistors page.

Typical Applications

The 500BA series of ceramic slab resistors and BA100 & 200 series of axial-leaded ceramic resistors are ideal for applications such as:

  • DC Coupling and Filter Cap Discharge
  • Voltage Balancing
  • Pre-charge / Inrush Limit
  • Voltage Divider
  • Filter
  • Snubber
  • Crowbar
  • Measuring
  • EMI / EFI Test
Posted in Uncategorized | Comments Off on HV ceramic resistors now available as axial-leaded and slab types.

Choosing a high voltage switch

Due to advances in semiconductor technologies, solid-state switches can now substitute thyratrons, ignitrons, spark gaps and electromechanical high voltage relays. TTL control input and low power electronics replace expensive heater supplies and drivers found in older systems. A high voltage switch can be chosen that meets application, system or load type criteria such as voltage, current, frequency and on-time. However, some extra work is required to ensure optimal performance of the switch in the application.

High voltage switches are composed of an array of semiconductors controlled by a sophisticated trigger mechanism. Overvoltages and high peak currents can be destructive so care must be taken when choosing a switch to ensure that specification limits are never exceeded. Also, the high dV/dt and dI/dt created by switching events requires care to be taken with circuit layout, wiring, shielding and grounding so that cross-talk and over-voltages are kept to a minimum.

Behlke HV switch HTS161-01How is power dissipated?

The equations below show how the power dissipated in the switch is proportional to the resistance R, capacitance CL and frequency f in each case. Typically not much can be done to escape the effects of the voltage but resistance, capacitance and frequency can be minimised to limit power losses.

equations for power dissipation in a HV switchPower dissipated inside a high voltage switch for frequencies <100Hz (left) and >100Hz (right)

The static on-resistance R will be given on the datasheet for each switch and the load capacitance CL should be known or estimated conservatively. The value for PD should then be compared with the value given on the datasheet.

HV switch spec table extraact

If the value for power dissipation is greater than that given on the datasheet then additional cooling options may be needed. The power dissipation for a variety of cooling options is usually listed to help identify the correct solution.

Different types of switch

Different switch technologies suit different applications. High voltage switches supplied by PPM use four main technologies to cover 1kV – 140kV and 15A – 16kA:

  • MOSFET – (Metal Oxide Semiconductor Field Effect Transistor)
  • IGBT (Insulated Gate Bipolar Transistor
  • MCT (MOS-controlled Thyristor)
  • SCR (Silicon-Controlled Rectifier)

Critical low frequency or resistive load applications may use a low on-resistance switch to help to reduce ohmic losses. Push-pull types have two switches in a half-bridge configuration. This enables the load to be actively discharged to provide a very fast falling edge.

Analysing and modelling the system

The final choice may come down to factors that only become apparent when analysing the entire system. Modelling the entire system using software such as PLECS or SPICE will enable you to optimize parameters and finalise your switch selection. For example, inductive loads or large stray inductance will generate reverse voltages which could damage the switch. Using freewheeling diodes can protect the semiconductors within the switch from these events.

Avoiding damage to the switch

The values specified by the manufacturer should not be exceeded as this may destroy the internal MOSFETs or the trigger circuit. Particular care must be taken with cable routing and shielding as large voltage and current transients on the high voltage circuit can induce significant instantaneous voltages on low level control lines. Subtle overcurrent and overvoltage events should be identified initially at low voltages so as not to create long term reliability issues in the full system at full load. Initial system testing should be done at low voltages to check there are no obvious issues. Overvoltages will scale with voltage – checks should be done to ensure low and high voltage signals remain in the correct limits determined by the switch or other components. Tests should be done at low operating voltages first before increasing to the full high voltage value.

PPM supply fixed on-time switches, variable on-time switches and pulsed power switch assemblies.  The full range offered by PPM can be found in the high voltage switches section.

Fixed On-Time Switches

  On-Time Description Maximum Voltage Maximum Current Switch On-time
Fixed thyristor/SCR switches Current Depending 4 – 150 kV 1 – 16 kA > 35 us
General Purpose Fixed MOSFET Switches Fixed 4 – 150 kV 15 – 200 A 100 – 300 ns
Low Impedance MOSFET Switches Fixed 0.5 – 40 kV 70 – 1600 A 150 ns
Ultra-Fast MOSFET Switches Fixed 3 – 12 kV 60 – 200 A 120 – 200 ns
Low On-Resistance Fixed MOSFET Switches Fixed 3 – 24 kV 60 – 1040 A 150 – 250 ns

Variable On-Time Switches

  On-Time Description Maximum Voltage Maximum Current Switch On-time
General Purpose Variable MOSFET Switches Variable 0.5 – 36 kV 12 – 640 A > 50 ns
High di/dt MOSFET Switches Variable 3 – 36 kV 200 – 3200 A > 300 ns
Low Capacitance MOSFET Switches Variable 3 – 140 kV 30 – 800 A > 60 ns
Low On-Resistance Variable MOSFET Switches Variable 0.5 – 21.6 kV 125 – 3750 A > 150 ns
AC MOSFET Switches Variable 1.2 – 36 kV 12 – 130 A > 50 ns
General Purpose IGBT Switches Variable 3 – 36 kV 800 – 9600 A > 0.2 us
Variable Thyristor/MCT Switches Variable 4 – 18 kV 3 kA > 1 us
Push-Pull MOSFET Switches Variable 2x 1.2 – 140 kV 2x 12 – 200 A > 50 ns
Pulser Switches Variable (2x) 3 – 12 kV (2x) 15 – 80 A > 50 ns

Pulsed Power Switch Assemblies

  On-Time Description Maximum Voltage Maximum Current Current Rise Rate
Pulsed Power Stacks Variable 30 kV 20 – 50 kA 10 – 30 kA/us

 

Pulsed Power Switch Assemblies

Pulsed power stacks

Posted in High Voltage | Comments Off on Choosing a high voltage switch

NEW high voltage programmable power supplies from HiTek Power

HiTek Power have released four new series of high voltage programmable power supplies: 400W, 600W, 3kW and 10kW. These products are available in 1U-4U rack mount units, depending on the power rating. Each product series ranges in output voltage from 1kV to 80kV*. The units are available in positive and negative polarities and feature arc count and extinguish (ACE) functionality

  • Local or remote control
  • Current or voltage control
  • Current ripple of <0.5%
  • Voltage ripple of <0.1%

OL400W / OL600W

OL3000

Series-OLS10K-10kW-high-voltage-power-supplies-01

OLS510K

The OL400W and OL600W series provide a single 400W/600W output suitable for electron/ion beam systems, x-ray systems and ion/chemical vapour deposition equipment. These units are available in 1U or 2U rack units and can be used in the most severe of electrical environments. Using air as the primary insulation method these units provide a power density of approximately 1W / cubic inch. The OL3000 and OLS10K series provide a single 3kW/10kW output suitable for x-ray, lab systems and heavy industrial electron beam welding and ion implantation. These are available in 3U or 4U rack units.

*60kV for OL3000 series

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Power electronics simulator PLECS v4.0 released

PLECS logo

New functionality included in PLECS 4.0

Version 4.0 of power electronics simulation platform PLECS® has now been released by Swiss developer Plexim GmbH. The latest version now includes the following additional capabilities:

New state machine block allows a modelling environment to support finite state machines that respond to discrete events.

Extended PLECS coder for PLECS Standalone can now produce code for a specific hardware target. The new External Mode enables you tune parameter values on the hardware target and display captured data on the host computer. The first supported target is the new PLECS RT Box; more targets will follow.
Automatic Initialization of Thermal States – PLECS can now automatically calculate initial temperatures for thermal capacitances based on their surrounding temperature.

New and Enhanced Library Components:

  • The electrical machines library has been extended with two new synchronous machine models based on look-up tables that can be imported from an FEM tool.
  • The Induction Machine with Saturation now features a Full VBR implementation, in which both the stator and the rotor are modeled as voltages behind variable reactances.
  • The mechanical library has been extended with a Planetary Gear Set model.

Extended Processor-in-the-Loop (PIL) framework – now supports STM32 F0, F1, F2 and F3 MCUs.

Reduction of algebraic loops with PLECS Blockset – Continuous inputs of a circuit block that do not have an immediate effect on any output are marked as non direct feedthrough inputs. This helps reduce the occurrence of algebraic loops in Simulink if you feed the output of a circuit block back to its input, e.g. to model a mechanical load.

Support for High-DPI Displays – the graphical user interface of PLECS now supports high-DPI displays on Windows and Mac OS X.

About PLECS

The PLECS® product family has been specifically developed to assist engineers with the design and implementation of complex power electronics systems. PLECS tools facilitate the selection of power-conversion topologies, allow for the sizing of components and thermal management systems and expedite the conception and realisation of sophisticated control algorithms.

PLECS_power_supply
PLECS-RT-Box

Posted in Simulation Tools | Comments Off on Power electronics simulator PLECS v4.0 released

EBG release 2kW thick film resistor UXP2000

EBG have released an ultra-high power resistor with a rated at 2000W*

The UXP2000 has an operating temperature range of -55°C to +150°C and a maximum working voltage of 5kV DC. Higher voltages and other temperature coefficients are available on request. Resistance tolerance is+/- 5% to +/-10%.

The datasheet is available to view via the PPM high power thick film resistors page.

About EBG resistors

EBG has been a leading manufacturer of non-inductive thick film resistors since 1977. The manufacturing process is state-of-the-art, producing precision resistors for high voltage, high power, and pulse loading applications. EBG offer:

  • Resistances 0.0005 – 30 GOhm;
  • Voltage range 1 – 96kV;
  • Power ratings of 1 – 1700 Watts
  • Tolerances of +/-0.1% to +/- 10%.

Normal lead time for standard or custom products is 8 weeks or less.

The EBG product range consists of over 350 standard and custom models of high voltage resistors, power resistors, pulse resistors, current sense resistors, load resistors, high power resistors, and matched divider resistor sets. Form factors available include cylindrical, flat, TO220, TO247, SOT227  and many custom power  footprints.

 

*2000W at 125°C bottom case resp. 60°C heat sink temperature

Posted in Resistors | Comments Off on EBG release 2kW thick film resistor UXP2000

New ultra-stable HV thick film resistor +/-5ppm over temperature

Austrian manufacturer EBG have released a thick film, high voltage resistor which delivers exceptional stability of only +/- 5ppm over a temperature range +25degC to +65degC.  The SHP52 is available in the range 100Mohm to 250Mohm and has a maximum operating voltage of 10kV DC.  EBG is a leading manufacturer of standard and customised high voltage and high power resistors.  EBG thick film resistors are available with voltage ratings up to 100kV and power ratings up to 2kW. The company have been manufacturing resistors for over thirty years for applications such as smart grid, drives, aerospace, medical and industrial applications.

The SHP52 is part of PPM’s range of high voltage thick film resistors.

Posted in Resistors | Comments Off on New ultra-stable HV thick film resistor +/-5ppm over temperature

High power resistors down to short lead-times

EBG high power resistors

Many of the standard high power resistors manufactured by Austrian company EBG are currently available on short leadtimes for small quantities. Metal film and thick film resistors for high power, high voltage and current shunt applications can be sourced in the UK via PPM. Custom products remain on a standard leadtime.  Visit the PPM Resistors page…

Current Shunt – Thick Film
High Voltage – Thick Film
Metal Film Resistors
Power – Thick Film

Ultra high power resistors
EBG high voltage resistors
ebg ultra high power resistor
ebg hxp thick film power resistor

ebg metal film resistors

Please contact PPM for further information on 01793 784389 or Email Us

Posted in Resistors | Comments Off on High power resistors down to short lead-times

Increasing the efficiency of high power inverters

High power IGBT-type inverters are being pushed to work at high frequencies e.g. >20kHz to avoid significant power losses and improve power density.  The stray inductance and high di/dt at each turn off cycle leads to a voltage overshoot.  The headroom required to allow for these overshoots significantly reduces the operating voltage at which the inverter can be rated.  Using a snubber circuit is the traditional solution to suppress the overshoot, however, there are component packaging technologies with exceptionally low stray inductance which address the problem without the size, cost and efficiency penalties of a snubber-based design.

Fig 1 - graph showing an IGBT

Fig 1 – Graph showing a switch-off event of an IBGT.  The blue line shows the voltage overshoot at the IGBT terminals. The purple line shows total current.

Potential solutions

  1. A snubber circuit – the traditional solution
  2. Reduce stray inductance using:
    1. Integrating DC link capacitors directly onto the bus plates
    2. Low inductance component package technology e.g. LinPak from ABB

1. The traditional solution – a snubber circuit

The classic solution for reducing voltage overshoot is the use of a snubber circuit to suppress the voltage spike – the most common topology being a resistor and capacitor in series across the switch. A snubber circuit dampens the overshoot since the voltage across a capacitor cannot change instantaneously.  Current flows for a fraction of a second, reducing the rate of voltage increase.

Fig 2 - snubber circuit

Fig 2 – diagram of a snubber circuit

However, on the down side, snubber circuits:

  • Are difficult to design for optimal performance – in particular, the voltage rating can be difficult to identify because of the complexity of transient waveforms
  • Reduce efficiency even when there is no load, since they are designed to dissipate energy
  • Increase the physical size of the design, not least because the snubber circuit must usually be mounted on a heat sink

2. Reducing stray inductance

The main benefit of reducing stray inductance stems from the fact that a snubber circuit can hopefully be removed entirely. This avoids the disadvantages listed above and leads to a smaller, more efficient and lower cost design requiring less thermal management.

There are two main options for reducing the stray inductance in a high power inverter:

  1. Integrating a DC link capacitor directly onto a DC link bus
  2. Using an IGBT module with low stray inductance and high contact area

Reducing the stray inductance of the module means less headroom required for the voltage overshoot which in turn means greater power density i.e.

  • Smaller, lower-rated components
  • Physically smaller design
  • Lower cost

Also, no snubber circuit to absorb energy means increased efficiency and reduced power loss.

2.1 Integrated DC link capacitor or DC link bus

SB Electronics (SBE) have shown that fully integrating a DC link capacitor with very low stray inductance onto the link bus means the voltage overshoot at each turn-off cycle can be improved by 20%.  This approach allows an increase in the operating voltage by 20% and therefore a significantly improved power density. Locating the elements closer together reduces resistance.  Lower resistance and lower inductance means improved efficiency, therefore, better power density and less thermal energy to dissipate.

SBE-test-kits

Fig 3 – Horizontally integrated DC link capacitors

Test kits of horizontally and vertically integrated DC link capacitors are available from PPM with a custom voltage and capacitance specification. Existing designs range in voltage from 450-1100V and capacitance 375-1500nF.

2.2 Packaging technology

In 2015, ABB announced LinPak, a new, open-standard phase-leg IGBT module topology for medium power levels. This module concept is designed to support fast and high current-density chipsets from 1200V up to 3300V. The exceptionally low stray inductance of 10nH allows a DC connection of very low inductance with sufficient area for high current densities.  LinPak offers several performance improvements over HiPak, including:

  • 65% improvement in voltage overshoot
  • Current density improvement >10%
  • Very smooth switching characteristics

LinPak medium power phase leg IBGT module

Fig 4 – the LinPak medium power phase leg IBGT module

Current rating per screw terminal – LinPak v HiPak

Module type Nominal current Phase current Current/M8 screw (phase terminals) Current/M8 screw (DC terminals)
LinPak 1000A 707A 354A 250A
HiPak 3600A 2546A 600A 600A

Current density – LinPak v HiPak v PrimePACK

Module type Current rating Footprint Current/Area
LinPak 2 x 1000A 100 x 140mm sq. 14.3A/cm 2
HiPak 3600A 140 x 190mm sq. 13.5A/cm sq.
PrimePACK TM 2 x 1400A 89 x 250mm sq. 12.6A/cm sq.

The total module inductance (including DC link) is 22nH compared to 27.5nH for HiPak – an improvement of 20%.  Moreover, the gates and auxiliary emitters are connected in parallel which means LinPak modules are easily paralleled with just one gate unit and without any significant de-rating.  Four LinPak modules in parallel can reduce the total inductance to only 5Nh, enabling a voltage overshoot reduction of up to 80% compared to a single HiPak module.

Click to see High Power Semiconductors 

Please contact us for more information or to order samples of IGBT modules or an SBE integrated DC link bus test kit 

Posted in Seminconductors | Comments Off on Increasing the efficiency of high power inverters

62Pak series of 1700V IGBT modules released for production.

Manufacturer ABB have announced that the 62Pak series of IGBT modules  is now officially released for mass production.   The 62Pak line-up consists of phase-leg modules in the 1,700V class available in either 300A, 200A or 150A current ratings. The state of the art SPT++ IGBT  diode chip-set offers best-in-class switching losses and ruggedness as well as a long lifetime in demanding applications thanks to high power cycling performance. These improvements have  been achieved by an optimized wire-bonding process, stamped spacers in the baseplate and main terminals plus a homogenous solder layer thickness.

Full switching performance up to 175°C

The 1,700V SPT++ chipset offers full switching performance up to 175 °C which allows higher over-load capability and/or improved safety margin to unexpected current surges.

Applications

The 62PAK is well suited for most power electronic applications such as:

  • Low-voltage and medium voltage drives
  • Static VAR compensators
  • Uninterruptable power supplies
  • Induction heating
  • Traction auxiliary converters.
Posted in Seminconductors | Tagged | Comments Off on 62Pak series of 1700V IGBT modules released for production.

Thermal modelling now easier and quicker for IBGT modules

IGBT HiPak modules

Thermal modelling data now available for IBGT modules from ABB

Thermal descriptions for ABB’s IGBT power modules can  now be downloaded for use in the PLECS simulation platform. Engineers can save time and reduce the risk of errors by using preassembled thermal descriptions created by the manufacturer, replacing the need for time-consuming manual input of the product specification data.

New ABB IBGT 62Pak 1700V module with SPT++ chipset

ABB’s newest IBGT module is a 62Pak, 300A phase leg module  The SPT++ chipset offers a highly rugged and reliable solution, specified to 175 degrees C.

The ABB SEMIS web-based simulation tool

Engineers who don’t currently use PLECS can use ABB’s own web-based simulation tool SEMIS.  Available via the PPM High Power Semiconductors web page, using a series of simple steps, users can evaluate the performance of ABB products for common converter applications and make preliminary component selections for their design.

thermal modelling image

PLECS image

ABB semis image

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More Information?

Telephone +44 (0)1793 784389 or email: sales@ppm.co.uk