CURRENT SWITCHING AMPLIFIER
21
CEDRAT TECHNOLOGIES
Current Switching Amplifier
18/12/2017
to a temperature rise of 33°C. Much of the time, the ambient temperature is low enough to not use a heat
sink and a fan permitting a substantial cost reduction.
For the external supply version, the power losses of the amplifier can reach 80W due to the increase of the
input voltage to 200Vdc.
The amplifier and the internal power supply are protected against over temperature for a heatsink
temperature of 80°C.
A recommended heat sink is the SK 42 (Fischer Electronik) with 150 mm x 200mm dimensions. It can be cut
to fit the dimensions of the product. Contact Cedrat Technologies for more information.
Worst case power losses with 20A continuous output current and 660W real power:
CSA96-IS
Typical Efficiency
Max Power Losses
Amplifier
98%
40W
Power supply
91%
65W
Those power losses are a worst case because the power losses in the power supply depends on the power
needed by the actuator and the amplifier.
8.3.
LIMITATIONS AND PROTECTIONS
8.3.1.Current limitation
An onboard current limitation is implemented to stay below the maximum output current. The default
limitation is tuned to 20A.
8.3.2.Energy recovery
The switching amplifier is well suited to drive reactive load. In this case, the switching amplifier doesn’t
consume the reactive power but only the active power of the actuator plus the losses in the power switching
functions.
Example:
A CSA96 providing 20A at 200Vpp with a sinus waveform (1kVA) to an ideal inductor consumes less than
40W due only to the power components losses of the amplifier. If the inductor is non-ideal, the amplifier will
also deliver the active power (Joules losses and iron losses). This active power cannot be higher than the
maximum power of the power supply (600W).
