▸
The peak current is only admissible for a short time (mostly 1 second) and de-
pends on the used diodes and their number.
▸
The rated current can be provided continuously by the power supply unit. Its value
depends on the cooling of the diodes, that means: the capacity of the used heat sink
and its ventilation.
Power
In practice, a maximum permanent power is specified for power supply units, since the
supply voltage is assumed to be constant. As the limitation in the power supply unit is
determined by the load carrying capacity of the diodes, the maximum permanent power
depends on the supply voltage and the type of supply.
Examples:
▸
Power supply 230 V
AC
, 2 phases, max. permanent current of the diodes 6 A
230 V
AC
× 2 × 6 A = 2.76 kW
▸
Power supply 400 V
AC
, 3 phases, max. permanent current of the diodes 6 A
400 V
AC
× 3 × 6 A = 7.20 kW
The maximum peak current depends on the type of diode used.
The protection is calculated as follows:
18.1.3 Motor
The motor is specified by the following details:
Peak current
The peak current defines the max. allowed motor current. The peak current is only al-
lowed for a short period of time (between 1 and 30 Sekunden) and depends on the used
magnetic material and the thickness of the windings. Normally, the motor manufacturer
defines the peak current applying during downtimes and during a rotating field. Gener-
ally, the values given on the motor data sheet are RMS values. SIEB & MEYER speci-
fies currents as sine peak amplitudes.
The RMS values are calculated by dividing these values by the factor √2.
Rated current
The rated current can be applied permanently to the motor. The value depends on the
cooling of the motor, the windings and the max. allowed motor temperature. Normally,
the motor manufacturer defines the rated current applying during downtimes and during
a rotating field. Generally, the values given on the motor data sheet are RMS values.
SIEB & MEYER specifies currents as sine peak amplitudes.
The RMS values are calculated by dividing these values by the factor √2.
The current version of the software drivemaster2 allows switching between the RMS
value and the sine peak amplitude (see “Settings → Program settings → View”). When
switching the view, the existing values are automatically converted into the new unit. The
default setting is the RMS value.
173Drive System SD2 - Hardware Description
Electric Performance Dimensioning
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