Technical Data
ANCA Motion
DS619-0-00-0019 - Rev 0
169
12
12.9.11
Effect of AC Input Voltage on DC Bus Voltage
For a delta connected supply or a single phase supply the input voltage will be approximately
( ) (
)
12.9.12
Effect of Bus Capacitance on DC Bus
Ripple
The selection of bus capacitance required for a user application is based on the amount of power required and
the amount of ripple desired. Increasing the bus capacitance can result in more power output (higher rms output
voltage as ripple reduces) and lower voltage ripple.
As well as this, sharing of the ripple current over more capacitors meaning less heating and longer life of the bus
capacitors. This also may reduce the requirement of regeneration resistors as the increase in capacitance lowers
the voltage increase of the capacitors. It may result in higher peak currents from the supply however, and
associated conducted harmonic current emissions, so recommended ANCA Motion inductors will no longer be
applicable.
The bus capacitors must support the DC bus voltage between charging. With three phase input at 50 Hz this
would be 1/300 = 3.33ms. An approximation to find the voltage drop is
where t = time(s) bus capacitance must support the load until it gets charged next, (3.33ms for three phase 50 Hz
and 10ms for 50 Hz single phase), I
rms
is the output current the drive is providing (A) and C is the bus
capacitance (F).
Note that this will give up to 1.5 times more voltage droop than will occur in reality. As the bus capacitance
increases and the load decreases this equation becomes more accurate. If exact voltage droop is desired then
please contact ANCA Motion applications engineering.
Note that with increasing drive bus capacitance the inrush current upon power-up increases and the internal soft
start resistor may not be sufficient to limit the charge current into the capacitors without blowing an upstream
fuse. Under all circumstances, the charge current must be kept to under 20A. The internal positive temperature
coefficient resistor is 50 Ohms. The maximum charge current at 240VAC input will thus be 340/50 = 6.8A.
12.9.13
Effect of Output Current on DC Bus Ripple
Voltage
12.10
Temperature De-rating
The AMD2000 3A and AMD2000 9A drives dissipate heat via heat sinks, but the AMD3 does not use a cooling
fan. In the unlikely event of fan failure under heavy load, the heat sink temperature will increase until it reaches
70°C, when the internal controller will stop power flowing from the drive to the motor and report a class 1
diagnostics error. Please see the graphs of ambient temperature and current rating below to assess safe thermal
operating area. Please note, these figures apply to 50 Hz sinusoidal output and power factor 0.8 on the
drive. Note that these curves may be scaled by duty cycle, so if the application only has the drive running for 0.5
duty cycle at 3 phase 55 °C ambient 240V delta supply then instead of 1.9A rms, the full 3A rms rating could be
used for 50% of the time.
