Released: 01/06/2010

Welcome to the Winter version of Westek News

Feeling the winter chill ? Grab a hot steaming cup of coffee, while we take you through some of our new products. We believe in sharing as much industry information with our customers and peers as possible. We have been able to pick essential news and information to keep you updated with Westek Electronics. The Westek Electronics team has been serving the market since 1996 and looks forward to being of continued service to you.

Subodh Bhatia,
Managing Director

In this Issue

• Schaffner introduces 690 Volt EMC filters
• Reducing harmonics
• Harmonics suppression for variable speed drives
• Filters
• Westek's WestSine active filters are ideal for changing harmonic patterns
• Protecting variable speed motors
• For EMC and CEPIC solutions Wurth are worth considering
• The latest from OPHIR in RF Amplifiers
• Picotest DMM has Giga performance

There are important advantages to changing from 415 to 690 Volt operation of motors and drives. For example in tunnel and other projects where large copper runs are in use, the reduced current resulting from the higher voltage reduces line losses by approximately 35%. It is also sometimes possible to use 415 delta-wired motors in star, thus drawing advantage of the higher voltage. Schaffner now has available four new EMC filters suitable for operation at 690 Volt.

A new series of EMC filters suitable for 690 volt reticulation systems is now available. The Schaffner filters cover applications including motor drives, industrial electronics as well as IT systems. They are generally suitable for Class A and B compliance.

Schaffner FN 258 HV book-style, three-phase EMC/RFI power line filter

The slim, book-style construction of the filters allow for easy integration into existing cabinetry and installation in proximity to motors, etc. The Schaffner FN 258 HV is a three-wire filter with C_y capacitors and resistors providing RFI filtering to earth. A version of the filter series suitable for IT does not have the resistors to earth. The FN 258 HV filter series is rated for 690 volt AC and line currents from 16 amps to 130 amps at 50C. The FN 258 HVIT series for IT applications has identical ratings.

Schaffner FN 3359 HV three-phase EMC/RFI power line filter

The Schaffner FN 3359 HV filter series is also a three-wire filter with C_y capacitors and resistors providing RFI filtering to earth and is also suitable for IT networks. The current ratings available range from 150 amps to 2500 amps. The topology of the filters is similar to the FN 258 HV series, mentioned above

Schaffner FN 3256 H, three-phase, four wire, power line EMC/RFI filters with neutral line filtering

The Schaffner FN 3256 three-phase, four-wire filters are light in weight and very compact thus allowing ready installation in existing cabinetry and mounting in proximity of motors, drive circuitry, etc. Typical applications include multi-axis machining centres, process automation as well as IT systems. The topology of the filters includes both C_x and C_y capacitors thus providing very low leakage currents thus permitting some medical applications. Current ratings range from 8 amps to 160 amps at 50ºC

Schaffner FN 3280 H, three-phase, four wire, power line EMC/RFI filters with neutral line filtering

The Schaffner FN 3280 series is identical in construction features to the above-mentioned FN 3256 H series and has similar applications,but has an extended current range from 8 amps to 600 amps at 50ºC.

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Reducing harmonics

There's more than one way of skinning the cat

Harmonics add significantly to current and energy consumption in modern electrical installations. Westek Electronics has a range of harmonics reduction solutions by way of passive and active filters as well as reactors available, and solid application advice. An exciting new range of Westek proprietary active filters, the WestSine range is now available.

Harmonics mitigation can be divided into two main areas; one being industrial and concerned with applications using variable speed drives and other three-phase (mainly) equipment such as induction heaters, burst and phase-controlled heaters for metallurgical treatment, steam raising, autoclaving, etc. The other main area is that of commercial electrical installations with electronic ballast loads for fluorescent lighting and IT equipment.

Traditional methods for suppression of harmonics include zig-zag transformers, reactors, and harmonic traps. Other methods include load segregation and the use of k-factor transformers. Strictly speaking the latter methods are better called ‘living with harmonics’ rather than suppression.

The industrial loads provide significant 5^th and 7^th harmonics as well as higher orders whereas commercial loads have big 3^rd harmonic contributions. Furthermore there are differences in load conditions. In a dynamic situation, rapid variation in load (e.g.: a fan motor starting up) will cause the harmonics profile to change rapidly over time along with the inrush current. In the case of an office building or shopping mall and generally in tenanted properties, shifts in IT loads will also cause rapid changes in harmonic patterns. This can also apply to lighting loads where there are frequent switching periods, e.g.: movement activated lighting control.

Harmonics suppression for variable speed drives

The most usual variety is the three-phase, 6-pulse drive. At the lower cost end of solutions to
reduce harmonics is the use of MTE reactors in series with the input to the drive.

Reactors (Chokes)
The new MTE RLW series DIN-rail mounting, line reactors provide useful functions in addition
to harmonics mitigation on the line side of variable speed drives. The properly selected RLW
impedance reactor in the input circuit virtually eliminates nuisance tripping of drives due to
voltage spikes originating from switching sequences including power company VAR
compensators. The MTE RLW reactors can also protect against short duration line sags. In
addition the reactors can also be used on the motor side of variable speed drives provided that
an 80% loading factor is applied (i.e. : for example; for 80 amps motor current a 100 amp
reactor is selected).

The RLW offers significant reductions in size, weight and cost while providing a high level of
drive protection. The RLW reactor is designed for adaptability and installation ease for OEM's,
integrators and panel builders.
Their smaller size with reduced weight over the standard reactors provides great benefits to
systems integrators as well as to installations requiring retrofitting.
MTE RLW reactors are manufactured to the exacting standards and are UL recognized and
CSA certified.

The range of RLW reactors covers 415 volts, 3-phase and 690 volts, 3-phase. The former
voltage rating comprises of motor ratings to 375 kW (full load current to 727 amps), and the
latter, motor ratings to 750 kW (full load current of 540 amps). Impedance levels can be
selected in3, 4 and 5% values.

DC link reactors can also be used, either by themselves or in combination with AC line
reactors (chokes).

The MTE DC Link Chokes are designed to reduce DC ripple as well as AC input harmonics.
In addition the MTE DC Link Chokes reduce di/dt slew rates and thus diminish significantly
stress placed on the insulation of other connected apparatus. Unlike input line reactors DC link
chokes do not reduce the input voltage at the fundamental frequency and therefore do not
reduce power to variable speed drives, etc.

Both passive and active filters can be used for harmonics suppression. Passive filters make
use of capacitors, resistors and inductors. Active filters basically use converter circuitry to
generate the distortion current required by the load. This is achieved by monitoring the current
to the load and generating the anti-phase component thus cancelling the distortion current at
the node of the load and incoming line.

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Filters

The MTE Matrix filters are very effective in harmonics reduction and offer the very latest in
harmonic filtering developments. The series D Multiple Three-Phase Inductor with a common
core-based filter has a patented unitary magnetic circuit topology and represents a compact
product readily built in to cabinets. The performance of the Matrix filters is in practice superior
to that of 12- and 18-pulse drives. These use of phase-shifting transformers which in practice
are very difficult to balance in terms of winding reactances provide harmonics reduction that is
far less than predicted by theoretical considerations. This becomes very noticeable under
dynamic load conditions in which case Matrix filters out-perform phase shifting transformer
systems.

The advantages of the new MTE MATRIX technology are very significant:

• Unsurpassed broadband technology and carefully designed components provide harmonics protection to the 25th harmonic and beyond without importation of harmonics or causing resonance

• Voltage spike protection

• Up to two-thirds of filter space saving, making retro-fitting in existing switchboards and MCCs an economical option

• Smaller capacitors

• Designed to outperform 18-pulse converter stages for variable speed drive DC-links. The MTE MATRIX series D reduces harmonic content in current to as little as 5% at full load!!

• And represents a 40% reduction over the harmonic level from many other commercially available passive filters

The MTE MATRIX series D is available as 415 and 690 volt filters with line current rating from 6 amps to 786 amps. Current ratings can be increased by paralleling filters.

Active Filters

Active filters are very effective in commercial installations. Such installations characterized by large numbers of electronic ballasts and IT equipment, generate very large harmonic distortion (often more than encountered in many industrial plants). Segregation of these loads is impossible and the use of active filters per phase on sub-distribution boards off loads the premises’ mains supply.

Commercial buildings, shopping malls, etc. have large fluorescent lighting and IT loads. Fluorescents, rather than having the older electro-magnetic ballasts, are equipped with the much higher ballast factor electronic ballasts. They have significantly higher harmonic distortion. IT loads are powered by SMPS and these power supplies have a high harmonic current. The THDI (Total Harmonic Current Distortion) is the additional component to the mains power frequency current.

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Westek's WestSine active filters are ideal for changing harmonic patterns

The Westek WestSine active filters are based on IGBT technology and utilise a somewhat similar method to that used in inverters and converters, to generate an anti-phase signal to the harmonic current components produced by the load. The filters are connected in parallel with the circuit they ’protect’ and draw leading phase angle current in order to provide DC link power for the converter. The latter consists of insulated gate bi-polar transistors (IGBT) operating in switching mode to generate the required harmonics balancing signals.

Wide-band current transformers in two of the phases measure the load current, and an electronic notch filter rejects the fundamental frequency component and passes the other components including non-harmonic (including transients) as well as harmonics and inter-harmonics to controlled attenuators.

The output from the notch filter-fed attenuators match the output signals to the IGBT switching unit so as to generate anti-phase current according to the rating of the downstream load. The control logic for the IGBT’s modulate their output to achieve this precise matching of the non-linear current components and harmonics ranging from the 2nd to the 51st order.

The Westek WestSine filters respond to harmonic load currents as well as other non-linear components, and in this way act in a distinctively different way to passive filters. Important advantages include the non-interference with the supply circuit impedance parameters, as there are no series elements in the filtering operation. In other words, resonance frequencies cannot arise. An additional advantage of the Westek WestSine active filters is their leading displacement power factor, which therefore counterbalances the usually lagging power factor of many loads.

Westek's WestSine active filters may be connected in parallel and in three-wire execution are available in current ranges from 25 to 300 amps and voltages (4-wire models range from 25 to 100 amps) and voltages to 690 volts. The three-wire models are suitable for non-triplen harmonics (eg: the third harmonic) situations, whereas the four-wire filters will remove triplens as well as all other harmonics.

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Protecting variable speed motors

Variable speed drives use pulse width modulation (PWM) to provide a variable frequency voltage to the motor. The very fast rise time of the pulses can cause dangerously high voltages to build up in the motor cable and wreak havoc with the motor insulation. Filters can be placed in the output of the variable speed drive to smooth the PWM pulses

MTE Series A dv/dt filters are designed to protect AC motors from the destructive effects of peak voltages typical of long cable runs between the inverter and motor.

The MTE dv/dt filter meets its maximum peak motor voltage specification (150% of bus voltage) with up to 300 metres of cable between the filter and the motor. It is also rated for a maximum dv/dt of 200 volts per microsecond. However, in specific applications, the filter has provided excellent performance with cable runs up to 900 metres. The dv/dt filter has a “3% insertion impedance” which ensures motor torque is not affected by added voltage drops from the filter. MTE Series A dv/dt filters are designed for use with inverters operated at switching frequencies between 900 Hz and 8 kHz

The dv/dt filter has a continuous current rating of 100% RMS and intermittent current of 150% for 1 minute and 200% for 10 seconds. 

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For EMC and CEPIC solutions Wurth are worth considering

Very frequently EMC solutions can be found through containment by way of using effective housing capable of shielding the environment from RFI emissions. To render the assembly a complete shield, gaskets, shielding mats and other Wurth products can be used. For isolation of DC rails, signal line, etc, Wurth ferrites and inductors are highly appropriate as well as cost-effective solutions. The Wurth CEPIC inductors are ideally suited to power supplies.

Wurth EMI shielding gaskets and shielding mats as well as braided material can be a vital element in controlling radiated RFI and EMI from the joints in metal cabinets used for mounting electrical, electronic and radio communication systems, and more generally in electro-mechanical construction involving challenging EMI/RFI isolation requirements. Special challenges include the seal of a hinged door of the cabinet as well as the correct bonding of sub-systems to reduce the problematic skin-effect caused by high frequency RF currents around the circumference of conductors.

Wurth ferrites are available in a vast range of executions to suit virtually any signal or power line EMI/RFI protection task. The range includes toroids and multiple pass-through ferrites such as Wurth Star-Tec EMI ferrites, patented Snap-On EMI ferrite cores with safety key for quick release, snap-on RFI ferrites for ribbons, Snap-on EMC ferrite sleeves; split EMI ferrite cores with nylon clamps; EMI ferrite ring cores; toroidal EMC ferrites; axial EMI ferrite beads; and EMI Ferrite plates.

SEPIC DC-DC power sources enhanced by inductor choice

SEPIC sources (Single-Ended Primary Inductance Converter) offer distinct advantages over fly-back sources although there is some degree of unfamiliarity with the technology holding back their application. The principles of operation of SEPIC topology for applications include DC/DC converters and also provision of information on suitable inductors for incorporation in the design is available from Westek Electronics.

In terms of the magnetic device to be used in SEPIC circuits, it is of course possible to use devices such as common mode power line filters but in order to get optimum performance, the use of shielded power transformers such as the Würth WE-DD series. These SMD devices are available in a wide range of L1/L2 values from 4.7 micro henries to high-energy storage coils of 220 micro henries. The devices exhibit very high saturation currents and are specifically designed for SEPIC duty and other switching regulators.

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Ophir RF amplifiers are now available in increased power range, frequency spread and feature packed, for example, including as standard IEEE and Ethernet interfaces.

The new Ophir 5000 and 5100 RF amplifiers have power outputs ranging from 50 watts to 500 watts and frequency spans to 4 GHz. Due to robust engineering and employment of the most advanced devices and components, the Ophir amplifiers achieve high efficiency operation with proven reliability.

The amplifiers utilize Class A/AB linear power devices that provide an excellent 3rd order intercept point, high gain, and a wide dynamic range. Functions include standby mode and rear panel IEEE-488 and Ethernet interfaces; front panel digital display; forward and reverse power readings; gain adjustment; ALC on/off; amplification mode(fixed Gain (VVA) or Automatic Level Control (ALC)); output mode; on-line or standby; as well as VSWR alarm threshold and fault indication including high Temperature, high VSWR, and ALC out-of-range.

These amplifiers accept a large range of signal import formats including CW/AM/FM/PM/Pulse. They are suitable for communication, EMC testing, Radar and jamming and electronic warfare.

Amplifiers are offered with a two year warranty and we can be supplied as complete amplifiers or as sub systems for OEMs.

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Picotest DMM has Giga performance

The Picotest M35XX series multimeters pack a punch. They are also very affordable, out performing many competitive makes. The Picotest M35XX series digital multimeters have 6 ½ digits resolution and ultra fast data acquisition rates.

The new Picotest M3510A/3511A digital multimeters have very fast data acquisition rates up to 50,000 readings per second (M3510A) and 10,000 readings per second (M3511A) as well as dual LED displays. The Picotest M3510A is capable of measuring temperature using RTDs and thermocouples in addition. Because of the dual display feature simultaneous readout of voltage and temperature is possible.

The new Picotest M3510A and 3511A six and a half digit DMMs with USB port are suited to R&D, scientific as well production and service tasks. Very importantly, the Picotest instruments are equipped with USBTMC compliant port. USBTMC stands for USB Test & Measurement Class. USBTMC is a protocol built on top of USB allowing GPIB-like communication with USB devices. From the user's point of view, the USB device behaves just like a GPIB device (example: ‘VISA Write’ can be used to send the *IDN? query and ‘VISA Read’ to get the response. The USBTMC protocol supports service request, triggers and other GPIB specific operations.

The Picotest M3510A and M3511A measure AC and DC voltage, DC and AC current, as well as capacitance and the M3510A also measures temperature for E, J, K, N, R, S and T thermocouples. The Picotest instruments are characterised by high accuracy and stability providing, for example, a voltage accuracy over a 24 hour period of 0.012% of reading. Voltage is measured to 1000 V DC (750 V AC), current to 3 amps AC/DC, and frequency/period to 300 kHz.

The Picotest M3500A range represents the latest release from Picotest, a company highly regarded for both innovative engineering and the high quality of its test and measurement instrumentation. Picotest also manufactures arbitrary function generators with LXI support and a series of universal counters with optional 20 GHz input.

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