Electric Performance Dimensioning
18 Electric Performance
Dimensioning
Experience shows that questions arise during the dimensioning of a drive when select-
ing output stages and power supplies. This chapter shall make clear the physical back-
ground and shall help to dimension correctly the electronic components.
18.1 Components
The following sections provide information on the electric performance dimensioning of
the drive components (output stage, power supply unit and motor).
18.1.1 Output Stage
The output stage of a drive amplifier is specified by the following details:
Voltage range
The maximum DC link voltage is limited by the used transistors and capacitors and the
minimum space between the strip conductors.
When an output stage with a maximum admissible DC link voltage of 325 V
DC
(class C)
is used, i.e. with an AC power supply of 230 V
AC
, the components will have an electric
strength of 600 V
DC
. The reserve is necessary in order to prevent damage in the case
of voltage peaks and the DC link voltages during the deceleration.
Current range
The current range specifies the maximum admissible currents. Distinction is made be-
tween peak and rated current:
▸
The peak current is only admissible for a short time (mostly 5 seconds) and de-
pends on the used transistors and their number.
▸
The rated current can be provided continuously by the output stage. Its value de-
pends on the cooling of the transistors, that means: the capacity of the used heat
sink and its ventilation.
▸
Due to the higher load of the power semiconductors in the output stage during a sta-
tic rotating field or low rotating field frequencies (f ≤ 5 Hz) the rated current will be
reduced by the factor √2 within this frequency range for the SIEB & MEYER devices
of the series SD2, SD2S and SD2T.
18.1.2 Power Supply
The power supply is specified by the following details:
Voltage range
The maximum supply voltage is limited by the used transistors, diodes and capacitors
and the minimum space between the strip conductors.
Current range
The current range specifies the maximum admissible currents. Distinction is made be-
tween peak and rated current:
172 Drive System SD2 - Hardware Description
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