Precor TRM 811.v2, Service Manual

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AC Lift System
– Motion Control
The motor used in the lift system is a "Permanent Split Capacitance" type, single phase AC motor.
What this means is that the motor incorporates the use of a capacitor to provide the torque required
to lift the weight of the user as well as the weight of the unit. Power to the lift motor is provided
directly from the AC coming into the unit.
In order to turn the motor in 2 directions, the AC motor has 2 separate windings, one for up and one
for down. AC1 has a continuous connection to the center / common connection of the motor.
The system has a 2A fuse to protect the components from over-current failure.
When a control signal is applied to the "UP" input, AC1control line is active and turns on the up
triac. This directs the AC2 connection to the up winding of the motor, causing the motor to spin in
the up direction.
When a control signal is applied to the "DOWN" input, AC2 control line is active, turns on the down
triac. This directs the AC2 connection to the down winding of the motor, causing the motor to spin
in the down direction.
Since the lift motor runs directly on the AC line voltage coming into the unit, it is important to note
that the lift motor is a different part number for a 120v unit than for a 240v unit.
Figure 8: AC Lift System - Motion Control