Diagnosing A Non-Working Stepper Module; Method To Troubleshoot A Ucp2 Stepper Module And Actuator; Overview; Ii. Quick Test Of Stepper Board - Trane CVHE Troubleshooting Manual

Diagnosing A Non-Working Stepper Module

Method to Troubleshoot a UCP2 Stepper Module and Actuator

I. Overview
The UCP2 Stepper module is used to drive a Stepper Motor, which is used to open and close a
valve or actuator. The big difference between a Stepper Motor and other types of motors, is that
instead of just making the motor turn, you can control the angular position of the rotor inside the
motor, and therefore control the position of your valve or actuator.
The Stepper Motor has two windings inside. To distinguish between the two, we call them
Winding 1 and Winding 2. The Stepper module contains one drive circuit for each winding. Most
of the failures you will probably deal with will result in the two internal fuses, F1 and F2, inside the
Stepper module to open. These fuses protect the motor from damage, and are not easily
accessible. Replacing these fuses in the field is not an acceptable option, because the original
fuses have been through some special UL testing. We cannot guarantee safety to the customer if
a blown fuse is replaced with another of a different type.
The Stepper Motor three states: Moving, Holding and Off:
1 In the Moving state, current flows bi-directionally through each of the two windings. The
frequency and amount of current is electronically controlled by the Stepper module.
2 In the Holding State, current flows one way through each of the two windings. The amount of
current is electronically controlled by the Stepper module.
3 The Off state occurs only when the Stepper module power is cycled. Until the Stepper
receives an order from the Chiller module to move, no current flows through the Stepper
Motor windings.

II. Quick Test of Stepper Board

A.This section will show how to test the main power points of the Stepper Board to get an idea of
where the problem is.
1 If the UCP2 Control Panel is unpowered, unplug the J2 connectors from the Stepper board
and continue to Section III to check motor and wiring resistances.
2 If the UCP2 Control Panel is powered, measure and compare the Power Input (J2) and the 4
Test Points at the right side of the Stepper board with
CVHE-SB-32A
Table 5
.
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