TMCM-160 Manual (V1.11 / August 8th, 2007)
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Copyright © 2006, TRINAMIC Motion Control GmbH & Co. KG
5.5 Under voltage behavior
•
The motor is switched on, if the supply voltage exceeds 9.0V
•
The motor is switched off, if the supply voltage falls below 8.5V
•
The current reduction due to low supply voltage may inhibit starting-up of the motor
•
EVALboard: Motor current is reduced to a lower value, if the voltage is below 12V. If motor load
is too high, the module goes into under voltage switch off again. This is due to the voltage drop
in the reverse polarity protection. Motor current is additionally limited at low supply voltages:
0.5A at 9V and linear increasing to 4A at 12V. To be sure to be outside this area, use at least 13V
supply voltage, due to voltage drop in the reverse polarity protection.
5.6 Demonstration
Application
You can use the Demonstration application for the TMCM-160 to set the module into operation. Please
remark, that you first should as a first step switch the module to remote controlled mode. You can
use the TRINAMIC TMCL IDE to update the modules firmware and to test / set all of the modules
parameters. If your motor shows instable behavior, you have to tune the PID regulator values. In
order to do this, you need to use the TMCL IDE.
5.7 Programmable motor current limit
The motor current limiting function is meant as a function for torque limiting, and for protection of
motor, power supply and mechanics.
Whenever the pre-programmed motor current is exceeded in a chopper cycle, the TMCM-160 calculates
a reduced PWM value for the next chopper cycle. New values are calculated 100 times a second. The
response time of the current regulation can be set using the parameter “current regulation loop
delay”:
A value of zero means, that in every 100Hz period, the current correction calculation is directly
executed and the resulting PWM value is taken. A higher current loop delay acts like a filter for the
current. The higher the delay value, the slower the current loop response time. A value of 5 (default)
leads to a current regulation response time of about 60 ms. On the mechanical side, a higher value
simulates a higher dynamic mass of the motor.
t
LIM
= 1 / (1 / 3s + 1 / (10ms * (1+x
CRLD
)))
x
CRLD
is the current regulation loop delay parameter, t
LIM
the resulting time for an 1/e response.
The actual current regulation time may be faster, depending on the PID settings.
Attention:
Please be careful, when programming a high value into the current regulation loop
delay register or if you want to work above the modules’ rated motor current: The
motor current could reach a very high peak value upon mechanical blocking of the
motor. If the short time current is not limited to a maximum of about 20A, this could
destroy the unit.
•
The current measurement can not detect currents below about 200-300mA. If the current limit is
set to a too low value, the motor may become continuously switched off.
•
The current limiting function is not meant as a protection against a hard short circuit.
•
The maximum motor current should never be set above the rated short time motor current,
because the current regulator can not operate correctly, if the current limit is set too close to the
measurement range limits.
