VMX Quick Setup Guide 13 | P a g e
PTC Thermistor Input
The VMX Series starter is provided with input terminals for connecting a PTC (Positive Temperature
Coefficient) Thermistor that may be imbedded in the motor. These
are specialized resistors imbedded in some motor windings that
increase in resistance as the temperature increases. When the
VMX Series detects that the PTC input resistance is too high, it
initiates a PTC trip, and displays [ PTc ] on the readout. This is
independent of the Thermal Register overload current protection
and provides supplemental protection for high motor ambient
temperature applications. Terminals for this input are provided
with a factory jumper that must be removed if the PTC input is
used. These are Terminals 9 and 10 located on TB1.
PTC resistors are also found in other devices such as bearings,
air receivers, oil or coolant reservoirs and air discharge systems that may require shutdown of the motor.
PTC Resistor Values:
The resistance must be less than or equal to 750 at 25ºC. If multiple resistors are used in the motor, the
sum of all resistors in series must equal or be less than this value.
Fault Signal
An optically isolated Triac output is dedicated as a fault indicator on TB1, terminals 11 and 12, labeled “Opto”.
The output Triac switch is rated for 10 - 250 VAC, 50 mA (maximum). If the three programmable Output
Auxiliary
Relays are being used for other functions; this output can easily
be hooked up to a PLC or small external relay to provide a Fault
signal. This Fault Output operation is permanently fixed at “Any
Trip”, duplicating the Relay setting 16 as shown in Table 5.6.10
of the Advanced Installation, Operation and Programming
Manual.
This output is permanently set to this function and is not
programmable.
To Next Page
Loading...
