Curtis 1205 Guide de dépannage télécharger pdf (Page 47)

Curtis 1204/1205 Manual, Rev. C

output and thus hold the current at the limit. Because the voltage across the power MOSFET

switch is high when it is off, the current limit comparison is inhibited during the off interval by

the current limit disable circuit. The current limit is set as follows:

1. During manufacture, the current limit is set by an internal trimpot (current

limit adjust) to the model’s nominal rating.

2. During operation at extreme high or low temperatures, current limit is re

duced to protect the controller from damage. From a thermal sensor (temp

sense) on the heatsink, signals are produced to cut back the current limit

at temperatures above 75°C or below -25°C (overtemp, undertemp).

3. During plug braking operation, the current limit is reduced to give an

appropriate motor braking torque. The plug braking current is set during

manufacture; it is also user-adjustable by a trimpot (plug current adjust

The plug current limit reference is derived from the current limit reference.

The transition to the plug braking mode is detected (plug detect) by monitoring the voltage across

the plug diode. When this diode becomes forward biased, it indicates that the motor ﬁeld has been

reversed and the controller has gone into plug mode. The current limit is reduced as described,

and the frequency of the oscillator is reduced from 15 kHz to 1 kHz, to allow ﬁner control of

the controller output while plugging. During plug braking operation, the acceleration circuit is

reset to a low level so that when drive operation resumes, the controller will go through a normal

acceleration ramp. When the motor has come to a stop, the plug diode will again become reverse

biased and the controller will revert to normal drive operation.

A-3

APPENDIX A: FUNCTIONAL DESCRIPTION

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Curtis 1205 Guide de dépannage Page 47