Eaton DS7 - Page 31

1 Device series DS7
1.14 Function
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com 27
Example of a current and torque curve for motor starts with a
soft starter
Figure 11: Reduced current rise
I
N
= Rated operational current at the operating point
n
N
= Rated speed at the operating point
① = adjustable current limitation
When used together with a PKE motor-protective circuit-breaker and a
SmartWire-DT connection, size 1 and size 2 DS7-34D…-D soft starters can
also be used to start motors with current limiting ①.
Figure 12: Reduced torque curve
n
N
= Rated speed at the operating point
M
N
= Rated-load torque of the motor during operation
M
L
= Load torque at the motor shaft
M
L
< M
N
at motor start
M
L
≦ M
N
in continuous operation
2
3
4
5
6
I/I
N
n/n
N
I
N
1
0.25 0.5 0.75 1
①
2
3
n/n
N
M
N
M/M
N
1
0.25 0.5 0.75 1
M
L