Siemens HT-direct - Page 33

Description, technical data
2.7 Definitions of the electrical data
A5E01083943A AB
Siemens AG Operating Instructions 2.02 1FW4
31
Maximum torque M
max
The maximum torque M
max
is the torque that is generated at the maximum current.
The maximum torque is briefly available for high-speed operations (dynamic response to
quickly change loads).
The maximum torque is limited by control parameters that are meant to prevent
demagnetization of the magnetic material.
Efficiency η
The efficiency η is the ratio between the power output and the power drawn.
Torque constant k
T
(value for a 100 K average winding temperature rise)
The torque constant k
T
is the quotient of rated torque and rated current at an ambient
temperature of 25°C:
k
T
= M
N
/I
N
Voltage constant k
E
(value for an average winding temperature rise of 20 K)
The voltage constant k
E
is the value of the induced motor voltage relative to 1,000 rpm at
25°C coolant temperature (liquid-cooled) or 40°C (air-cooled).
The phase-to-phase RMS motor terminal voltage is specified for the 1FW4 motors.
Winding resistance R
ph
The resistance of a phase at a room temperature of 20°C is specified.The winding has a star
circuit configuration.
Inductance L
D
The rotating field inductance is specified.
Electrical time constant T
el
The electrical time constant T
el
is the quotient of the rotating field inductance and winding
resistance. T
el
= L
D
/R
ph
Thermal time constant T
th
The thermal time constant T
th
defines the temperature rise of the stator winding when the
motor load is suddenly increased (step increase) up to the permissible S1 torque. The motor
has reached 63% of its final temperature after T
th
.