Page 129 - TBIS_15194-2019_(EN)_3nd
P. 129
TBIS 15194:2019
The relationship between motor current I and torque M is linear according to:
M = k(I – I 0)
where
M torque [Nm]
k torque constant [Nm/A]
I current [A]
I 0 no load current [A]
The relation of power is:
where
P output-power[W]
n speed[rpm]
Figure B.2 — Speed-power diagram function
Because the natural speed-torque-diagram is a linear falling function (at constant voltage U)
the output-power torque function (see Figure B.1) and the output-power-speed function is a
parabolic one (see Figure B.2). Therefore, if the torque falls linear from M cr (torque at P cr –
continuous rated power) to zero, the motor current falls linear to I0 and the power P falls
progressively from Pcr to zero.
The corresponding relations are:
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