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SEVEN COMMON EMC IMMUNITY TESTS Magnetic Field Testing: simulates the effects of a

magnetic field. Typical devices requiring this type of immunity testing include CRT monitors and electrodynamic microphones.

Voltage Drop Testing: tests the impact of a sudden voltage dip or other power interruption on a piece of equipment. This replicates the effects of brownouts, as well as the normal fluctuations in the AC mains network. Surge Immunity Testing: electromagnetic surges can be caused by indirect lightning strikes and routine power switching events. Can lead to arcing, cabling breakdowns and motor damage. Requires specialised EMC test equipment.

Conducted Immunity Testing: simulating potential disturbances from other devices powered by the same power network, or inductively coupled onto its I/O lines. Uses CDNs, BCI probes and direct voltage injection equipment.

Radiated Immunity Testing: evaluates functioning of a device when exposed to different electrical field sources, such as mobile phones, microwaves and Wi-Fi routers.

Electrostatic Discharge (ESD): occur as a result of built-up static electricity. Can cause IC port damage, communication failures and damage to LCD screens. Performed with EMC test equipment that creates a short burst of energy, typically at 4kV and 8kV.

Electrical Fast Transient (EFT): disturbances caused by inductive load switching on the power grid. A burst generator is used to mimic the effects of electrical switches, motors and relays and fluorescent lamp ballasts.

35 to 40%. With power regeneration, the system does not need large oil-filled resistor banks for removing excess energy. The SPI inverter used is a bi-

directional DC-fed drive for controlling AC motors. The inverter has a DC bus coupling and also allows the user to have access to the regenerative operation of a drive system. In this manner, the braking energy of the drives can be directly transmitted to a motor driven drive via an intermediate circuit coupler or, as in the case of I2

PS, fed back into the grid. The upgraded drive system of the

exciter is now part of a surge generator plant with a peak short-circuit power of 298MVA. Short circuit tests in the low voltage range with test currents up to 300kA are therefore possible. In the case of lengthy test setups, it is now possible to stop the surge generator to save energy, without losing time. Before modernisation, this was only possible a maximum of three times a day due to the oil-cooled starting or braking resistors. The necessary cooling phases required for the intensely heated oil are eliminated. “The ability to stop and start the

surge generator as and when needed is a 8 /// EMC Testing 2017

❱❱ The 9000X Series of the modular DC bus drives from Eaton includes numerous regenerative units and frequency converters with ratings from 0.55 to 2,750kW at 460 and 690V

❱❱ Frequency Converter: The air cooled frequency converter (SPI) with the regenerative unit (SPA) of Eaton transfers braking energy from the motor back into the grid

decisive advantage of the modernisation for us,” said Klaus Heidelberg, manager Energy/Switching Power, I2


“Moreover, the new drive is much more energy-efficient than the old slip ring motor. The total energy saving is

achieved in three ways – the energy efficient drive system, the energy saved by switching off the surge generator during set up and the return feed of the braking energy into the grid, which was previously lost in the form of heat.” EE

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