TMCM-1181 V3.0 Hardware Manual (Rev. 0.90 / 2015-JUL-10)

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stallGuard2™ stallGuard2 is a high-precision sensorless load measurement using the back EMF on the

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 goes to zero or

near to 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 1.1 stallGuard2 load measurement SG as a function of load

coolStep™

coolStep is a load-adaptive automatic current scaling based on the load measurement via

stallGuard2 adapting 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 reducing cost.

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 50% torque reserve

Figure 1.2 Energy efficiency example with coolStep