7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 27 of 57
3.1.2 Thermal Protection: Stall Protection (14)
Stall protection can be applied where the thermal characteristic does not offer sufficient protection against stalling
during running or during a locked rotor condition on starting.
Pick up is initiated when any phase current is above Gn 14-n Setting
Gn 14-n Delay is initiated when the measured current exceeds the Gn 14-n Setting
The time delayed overcurrent elements are enabled for the following ‘Control’ criteria:
Gn 14-n Control = None: Element operation begins when current exceeds Gn 14-n setting.
Gn 14-n Control = Stopped: When the relay has determined a motor stopped condition this control is
latched for the period where the current increases from Istopped for the time until the current falls below
the Gn 14-n setting level. Element operation begins when current exceeds Gn 14-n setting
Gn 14-n Control = No Accel: A tachometric ‘zero speed’ switch mounted on the rotor shaft can be used to
identify that the motor is not running up to speed. A relay binary input programmed to ‘No Accel’ can be
connected to this switch. Element operation begins when current exceeds Gn 14-n setting and the relay
has determined that the motor is not starting.
Gn 14-n Control = Running: Element operation begins when current exceeds Gn 14-n setting and the
relay has determined a motor running condition. See section 3.1.
Operation of the stall elements can be inhibited from:
Inhibit 14-n A binary or virtual input
14-n
Inhibit 14
Enabled
Disabled
&
Control
General Pickup
IA
IB
IC
Gn 14 Element
Gn 14n Delay
≥
1
>
>
>
En
Gn 14n Setting
Figure 3-4 Stall Protection (14)
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