EMMA 3G PWM (pulse width modulation) control The EMMA 3G MOSFET’s switching frequency is c.16.7 kHz. This means that they switch
on c.16,700 times per second or once every c.59.88 microseconds. The period they remain
on each time varies from c.0 microseconds (to provide 0% of the total power rating of the
heater) to c.59.88 microseconds (to provide 100% of the total power rating of the heater).
The smallest adjustment to these periods is 0.44 microseconds or 0.73%. A microsecond is
one millionth of a second.
The EMMA 3G unit adjusts the “on” time of these pulses each cycle of the control software.
The control software cycle time is 84 milliseconds for the standard EMMA Cascade system;
98 milliseconds for the EMMA GVS Cascade system and 110 milliseconds for the CentricaBritish Gas EMMA trial system. A millisecond is one thousandth of a second.
The voltage of the mains supply alternates at a frequency of 50 Hz following a sine wave
pattern or cycle that repeats approximately every fiftieth of a second.
Alternating pattern of mains supply voltage – during one fiftieth of a second
The power supply from the EMMA 3G unit follows this sine wave pattern or cycle. The power
supplied by the EMMA 3G unit is switched “on” c.334 times every full cycle; or c.83.5 times
every quadrant.
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c.334 pulses of power going to a heater when the EMMA unit is providing c.25% of the total
power rating of the heater
(four quadrants of 50 Hz cycle; one fiftieth of a second)
c.83.5 pulses of power going to a heater when the EMMA unit is providing c.25% of the total
power rating of the heater
(first quadrant of 50 Hz cycle; one two hundredth of a second)
EMMA… Puts You in Control
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