Elevator Mechanic Practice Exam

How can you change the direction of a new VV-VF door operator that operates in the wrong direction?

1. Change the control motor

2. Change the door motor

3. Change the phase sequence

4. Replace the drive belt

The correct answer is: Change the phase sequence

To change the direction of a new Variable Voltage-Variable Frequency (VV-VF) door operator, adjusting the phase sequence is the appropriate method. In electric motors, particularly those that operate on alternating current, the direction of rotation is determined by the sequence of the phases applied to the motor. By changing the phase sequence — which involves modifying the order in which the electrical phases are connected to the motor — the motor's rotational direction can be reversed. This is crucial in systems where the proper motion of components, such as doors, is necessary for safe and efficient operation. The other options focus on components that, while they may affect the operation of the door operator, do not directly influence its rotational direction. For example, changing the control motor or the door motor could potentially address other issues but would not specifically address the need to reverse the direction of operation without proper phase adjustments. Similarly, replacing the drive belt concerns the connection between the motor and the door but does not impact the motor's rotational direction. Thus, adjusting the phase sequence is the direct and effective solution for changing the operational direction of the door operator.