EMMA 3G Compliance

EMMA 3G Compliance and Development. 

Compliance Test Results, May 2012

Compliance testing results for the production version of EMMA 3G. These tests were conducted in May 2012, on a random sample unit of EMMA before shipping. Additional technical documentation is available in the Installers section.

For more information about the results and how to interpret them, see our FAQ section on EMMA Compliance Testing. For an overview of how EMMA's pulse width modulation works (PWM), read How EMMA 3G PWM control works.

The plots from the Conducted Emissions Tests are shown at 25%, 50% and 75%. They show that the conducted emissions from EMMA are well below the relevant limits.

The Temperature Test Results are from a unit left running at 50% power connected to a 3kW heater until the temperature of the filters reached steady state. This shows that the filters stabilised at circa 47 degrees C. The filters are rated for ambient conditions of 100 degrees C and don't saturate until they reach circa 120 degrees C. EMMAs filters are thus operating well within their specified limits.

Harmonics Test Results are shown at 25%, 50% and 75%. The results show that EMMA is almost completely harmonics free and well within all the required limits: EMMA creates little or no harmonics on the DNO's network. The results show that EMMA does not impact the DNO's network with harmonics, when compared with the existing harmonics on the network without EMMA. The test results are from zero to one hundred percent in increments.

Results also show how efficient EMMA is. It draws only circa 2.9 watts in the idle state.

Development of EMMA 3G for compliance

The EMMA 3G was developed over 4 years ago to provide High Speed Pulse Width Modulation of power to resistive heating loads in a compliant manner.

The EMMA 3G has been independently tested by Compliance Engineering Ireland (CEI) in accordance with the standards we have agreed are correct with the UK DNO's such as SPEN and SSEPD. It has also been independently successfully tested by Imperial College for Scottish and Southern Energy Power Distribution as well as being independently tested on trial sites for small and larger scale export control by Scottish Power.

The EMMA 3G unit uses High Speed Pulse Width Modulation technology to produce a Pure Sine Wave output that varies in amplitude based on a control signal.

EMMA with Export Control DNO compliance testing

The EMMA 3G with export control is our older generation unit which has been developed in collaboration with several large UK DNO's over during last five years. The initial concept was put together in October 2010 at the request of Mr Bill Halliwell of Electricity Northwest (then United Utilities). The aim was to provide a means of manging on-site load in a way that ensures that export from sites with grid-connected generators is limited to that permitted by the DNO... with absolute certainty.


This is achieved primarily by adjusting the amount of power sent to suitably sized resistive loads on site in a way that ensures that the difference between generator output and site load is always precisely the same as or less than, the permitted export limit. The resistive loads are typically comprised of a battery of 3kW immersion heaters in a buffer tank (or in-line heater) serving on-site loads including hot water, heating, dairy wash down, dairy sterilisatiion, drying (timber, grain, chicken droppings) and swimming pools.

The first challenge was to develop a control system that does this in a harmonics "free", seamlessly smooth (i.e. flicker free) way that ensures there are no associated power quality issues. We have worked very closely with Scottish Power Energy Networks (SPEN) and Scottish and Southern Energy Power Distribution (SSEPD) on this aspect of the design during the last two years... both in the field where many trial installations with generators ranging in size from c.10kW now going up to c.250kW (both PV and Wind Turbines) and export limits ranging from 0kW to 50kW were intensely monitored; and in the laboratory at Imperial College London where a number of EMMA units have been intensively tested on behalf of SSEPD. 

The second challenge was to make these devices "fail safe". This is achieved in two ways. The units themselves maintain a running real-time measurement of power exchange with the grid  i.e. import or export. This figure is compared with the permitted export limit every c.10 milliseconds and is used to generate a running 30 second average. In the event of this average exceeding the permitted limit by an agreed margin (typically 5 Amps per phase) for more than a permitted period (30 seconds) [this is required to cope with instantaneous variations when large site loads are switched off] the system isolates the generator by tripping the G59 isolator for an agreed minimum period. There are further protections built into the system such as powered on isolator control (i.e. the generator is isolated in the event of an internal PSU failing) and delayed start up (which ensures that the generator isn't connected before the 30 second running average is established).

The second "fail safe" protection consists of additional reverse flow G59 detection and isolation... which is normally used on sites with large RE generators i.e. above 100kW.

Compliance Documentation

Our compliance certs can be downloaded under the documents tab of this section.

EMMA 3G Compliance FAQ

EMMA Compliance Testing

Where can I find Compliance Test Results for EMMA?

See our compliance documentation under products adn compliance and then select the appropriate product.

Where do you carry out Harmonics tests on EMMA?

We measure harmonic currents generated by our EMMA units using standard test equipment that belongs to Compliance Engineering Ireland, a highly respected commercial EMC test lab in Ireland. Test equipment is subject to regular independent inspection and certification. This measures current on a cycle by cycle basis using validated techniques.

What results does EMMA get? Why do you not show 100% test results?

The results fall far below the relevant limits at all EMMA % settings. We have shown the 25%, 50% and 75% results because they are indicative of the results across the full output range, with the exception of 0% and 100% where the harmonic current levels fall below the threshold of meaningful measurement.

I am puzzled by your harmonic test statements; for instance, for the 25% power case, the plot appears to reveal that the principal harmonic is the 26th (26 blue peaks in one green cycle), not the 13th; while the spectrum below implies that the third harmonic is the worst. As the power is raised the harmonic content of the current clearly falls, yet the test results statements claim it is rising. These data seem irreconcilable.

You may be misreading the harmonics test result graphs. The measured harmonics are shown at blue bars at each harmonic frequency. The values shown are calculated in accordance with the measurement method over a ten minute period. They are so low that they barely show on the 50% chart. The red and blue lines are the allowable limits.

Your website describes the modulation as phase angle firing of a thyristor. This should give rise to a sawtooth - like waveform with sharp edges at gate off, least extreme near 0% and 100% power. The current waveforms actually observed are sinusoidal with modulation by the 26th harmonic. Can you explain why?

We are modulating the width of the pulses of power supplied to the heating element using MOSFETs (which switch almost instantly). Each individual pulse of power is virtually rectangular in wave form apart from an extremely short duration spike that occurs at the end of each pulse and a string of associated harmonics. This spike and the associated harmonics are removed by a filter pack within the EMMA unit.

The sinusoidal plot shown on the top of the test result sheet is a snap-shot of current and voltage measured on a cycle by cycle basis. This changes continuously during the ten minute test period and is of very limited significance because of the much higher switching frequency of the EMMA unit.

EMMA 3G Declaration of Conformity

This document shows the EMMA 3G Declaration of Conformity 


EMMA 3G Compliance MOSFET Temp

This document shows the EMMA 3G MOSFET Temperature Test results. 


EMMA 3G Compliance Idle Power Consumption

This document shows the EMMA 3G Idle Power Consumption test showing the EMMA 3G consumes 3.3W in standby mode.


EMMA 3G Compliance Harmonics 25%

This document shows the EMMA 3G Harmonics Test results run at 25% duty cycle on a 3kW load.


EMMA 3G Compliance Harmonics 50%

This document shows the EMMA 3G Harmonics Test results run at 50% duty cycle on a 3kW load.


EMMA 3G Compliance Harmonics 75%

This document shows the EMMA 3G Harmonics Test results run at 75% duty cycle on a 3kW load.


EMMA 3G Compliance Conducted Emissions Charts

EMMA 3G SP15NN Conducted Emissions Test results


EMMA 3G Compliance SP15NN Test 1

EMMA 3G SP15NN Compliance Test 1 of instantaneous power testing


EMMA 3G Compliance SP15NN Test 2

EMMA 3G SP15NN Compliance Test 2 of instantaneous power testing


EMMA 3G Compliance SP15NN Test 3

EMMA 3G SP15NN Compliance Test 3 of instantaneous power testing


EMMA 3G Compliance SP15NN Test 4

EMMA 3G SP15NN Compliance Test 4 of instantaneous power testing


EMMA 3G PWM Control

EMMA 3G an explanation of how the EMMA 3G unit is performs modulation of power using Pulse Width Modulation.

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