TMCM-1076 Hardware Manual • Hardware Version V1.10 | Document Revision V1.00 • 2018-JUN-25
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1.3 stallGuard2
stallGuard2 is a high-precision sensorless load measurement using the back EMF of the motor coils. It
can be used for stall detection as well as other uses at loads below those which stall the motor. The
stallGuard2 measurement value changes linearly over a wide range of load, velocity, and current settings.
At maximum motor load, the value reaches zero or is near zero. This is the most energy-efficient point of
operation for the motor.
Load [Nm]
stallGuard2
Initial stallGuard2 (SG) value: 100%
Max. load
stallGuard2 (SG) value: 0
Maximum load reached.
Motor close to stall.
Motor stalls
Figure 3: stallGuard2 Load Measurement as a Function of Load
1.4 coolStep
coolStep is a load-adaptive automatic current scaling based on the load measurement via stallGuard2.
coolStep adapts the required current to the load. Energy consumption can be reduced by as much as 75%.
coolStep allows substantial energy savings, especially for motors which see varying loads or operate at a
high duty cycle. Because a stepper motor application needs to work with a torque reserve of 30% to 50%,
even a constant-load application allows significant energy savings because coolStep automatically enables
torque reserve when required. Reducing power consumption keeps the system cooler, increases motor
life, and allows for cost reduction.
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
0
50
100
150
200
250
300
350
Efficiency
Velocity [RPM]
Efficiency with coolStep
Efficiency with 50v torque reserve
Figure 4: Energy Efficiency Example with coolStep
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