MPE Limited
Hammond Road
Knowsley Industrial Park Liverpool
L33 7UL
T: +44 (0)151 632 9100

Standard Performance 1200A Single Line HEMP & IEMI Filter

1200A HEMP Insertion Loss Graph


1200A Power Line HEMP filter independently tested and certified by Jaxon Engineering & Maintenance as meeting the pci requirements of Mil-Std-188-125-1 and -2 and Def Stan 59-188 parts 1 and 2 for E1 and E2 pulses. The filter has no internal parallel filter circuits and features inductive input to offer both good continuous wave EMC performance and superior transient handling performance even on supplies with low source impedance. The filter is fitted with high-energy transient suppressors. Filters are supplied as single line units for ease of handling and installation but four filters are normally used together for filtering three phase plus neutral supplies.

Customised end enclosures are normally fitted to provide screening of input and output terminals, and to interface with the customer’s connection requirements.

All MPE HEMP filters are tested using the test methods defined within the following standards and meet or exceed the relevant performance and/or safety criteria defined within these standards:

CISPR17:2011/BS EN 55017:2011
LVD 2014/35/EU


  • 250V and 277Vac versions
  • 4 lines for 250/440Vac or 277/480Vac supplies
  • Utilise MPE self-healing feedthrough capacitors for significantly improved reliability
  • Significantly smaller & lighter than traditional solutions
  • Lower heat dissipation than traditional solutions
  • High energy transient suppressors for high reliability
  • No internal paralleling of filter components
  • Complies with IEC 950 requirements
  • Reliable capacitor technology proven over 25 years
  • Very low residual pulse current – high safety margin



Rated Voltage Single phase 250Vac 50/60Hz or 277Vac 50/60Hz
Three phase 250/440Vac 50/60Hz or 277V/480Vac 50/60Hz
Test Voltage 2250Vdc each line to case (Prior to fitting   transient suppressors)
Rated Current per Line @50C* 1200A
Insulation Resistance >100MΩ (Prior to fitting discharge resistors)
Discharge Resistors Fitted internally from each line to case
Discharge Time to below 34V <60s
Maximum Temperature Rise on Full Load <25ºC
Full Load Operating Temperature Range -40ºC to +50ºC
Leakage Current at 250Vac 50Hz <14A
Maximum DC Voltage Drop per line at 1200Adc 60mV
Peak Surge Current of Transient Suppressors 70kA (8/20μs)
Varistor Voltage Rating 250V/440V 275Vac
277/480V 480Vac


Typical insertion loss In 50Ω system with / without load

Frequency 10kHz 100kHz 1MHz 10MHz 100MHz 1GHz
Minimum Insertion loss 20dB 40dB 60dB 80dB 80dB 80dB
Typical Insertion Loss 45dB 65dB 95dB 100dB 100dB 100dB


MIL STD 188-125-1 acceptance test, short pulse current injection, wave shape 20/500ns
Input pulse amplitude 250A 500A 1000A 1800A 2500A
MIL-STD-188-125 residual requirement <10A <10A <10A <10A <10A
Typical filter residual let-through (277/480V version)(250/440V version is less) <3A <4.5A <6.5A <7A <7.5A


MIL STD 188-125-1 acceptance test, intermediate pulse current injection, wave shape 1.5/3000ns
Input pulse amplitude 250A
MIL-STD-188-125 requirement No filter damage or performance degradation
Typical filter response No filter damage or performance degradation


Material:                        Stainless steel

Finish:                            Paint (base paint free)

Approx. Weight:             300kg



Four filters are normally used together for use on three phase systems. Filters are supplied as single lines for ease of shipping and installation, and are designed for mounting in close proximity. Filters should be mounted on clean unpainted mounting surface to ensure a good low-impedance earth bond and RF connection is made to the underside of the filter.

Because every installation of such high current filters tends to be different, they all generally need customised shielded termination enclosures to interface with the cables or busbars used for power connections.

Both ends of the filter are provided with blind inserts to make a good quality shielded interface to external terminal chambers. Wire mesh gaskets are needed between the filters and the terminal chambers, and these gaskets can be provided by MPE, if required.

MPE can also provide customised terminal compartments to interface with these filters, or alternatively, the user can provide his own but must ensure that clean unpainted and flat mating surfaces are used to interface to the filter via the wire mesh gasket. the interface fixing bolts (M6) should be tightened to a maximum torque or 2.5N-m. (22lbf-in)



Relevant safety standards have been adhered to in the design and manufacture of these filters. However, all capacitors will store charge after power has been removed and must be treated with respect as a shock can be lethal if the voltage and charge are high enough. Even though discharge resistors are fitted to this range of filters, terminals should always be shorted to earth prior to touching to ensure the capacitors are fully discharged.

The user should ensure he is familiar with restrictions on capacitance value, earth leakage current, test voltage, and safety labelling requirements, which may be applicable to his particular installation.

These filters must be solidly and permanently earthed, both for safe operation and to achieve optimum EMC and pulse performance.



250V version for use on supplies up to 250/440Vac 50/60Hz       Part number DS33738

277V version for use on supplies up to 277/480Vac 50/60Hz       Part number DS33738/480

Wire mesh interface gasket                                                           Part number 64/829712