The requested setup combines three separate jobs: motor protection, speed control, and motion sequencing. The LARSEN & TOUBRO CX 2000 can run the three-phase 0.75 hp motor from terminals and accept a potentiometer reference, but an exact forward revolution followed by an exact reverse revolution needs position feedback and sequence logic. Configure from the drive manual and motor nameplate; the model identifiers alone do not define terminal assignments or parameter numbers.
Reject the quick fixes that miss the problem
| Quick fix | Why it fails | Use instead |
|---|---|---|
| Search for a “one rotation” parameter | A normal VFD regulates speed or frequency. A run command remains active until control logic removes it; the drive does not know shaft position without suitable feedback. | Add a one-pulse-per-revolution sensor or other position feedback and sequence the commands externally. |
| Guess parameter numbers from another drive | Terminal-function and command-source numbers are product-specific. A wrong assignment can disable Stop, create unexpected starts, or select the wrong analog input. | Use the wiring diagram and parameter table for the exact CX 2000 variant. |
| Enter only the 0.75 hp value | Power alone does not define rated voltage, current, base frequency, or rated speed. Incorrect motor data weakens protection and control. | Copy every requested motor value directly from the motor nameplate. |
| Use momentary buttons with two-wire control | Two-wire control expects maintained contacts. A momentary Start button may run only while pressed or behave differently after a power cycle. | Select three-wire terminal control when the intended station has momentary Forward, Reverse, and Stop buttons. |
| Use a timer for exactly one revolution | Acceleration, load, slip, braking, and speed-reference changes alter travel during a fixed time. | Use a shaft or machine-position sensor when one revolution must be repeatable. |
Define what “one forward and one reverse” means
Resolve the motion requirement before wiring the station. The phrase has two practical interpretations:
| Required behavior | Control architecture | Stopping basis |
|---|---|---|
| Select continuous forward or continuous reverse | Drive terminal control with interlocked direction commands | Stop push button or removal of the run command |
| Exactly one revolution forward, then one revolution reverse | External sequence controller plus position feedback | Sensor event or position count for each direction |
For selectable continuous direction, three-wire control is the likely operating mode: momentary Forward Start, momentary Reverse Start, and Stop. For a single-revolution cycle, the push button should request a cycle from a PLC, smart relay, or equivalent controller. That controller commands forward, reads the revolution sensor, stops the motor, waits for motion to cease as required by the mechanism, commands reverse, and stops on the return event.
A proximity switch and one target per revolution can provide a simple count. Place the target and sensor so the initial target state cannot be mistaken for completion. If stopping accuracy is tighter than the travel accumulated during deceleration, use a slower approach, mechanical indexing, braking hardware, or a positioning-capable motion system selected from its documentation.
Enter only the motor and operating data you can verify
Record the drive nameplate as LARSEN & TOUBRO CX 2000, PR 151208-46830001, and LTVF-C40003BAA. Record the motor as three-phase and 0.75 hp, then read the remaining values from its nameplate. Do not infer supply voltage or drive rating from the model string.
| Setting group | Value source | Reason |
|---|---|---|
| Motor rated power | Motor nameplate: 0.75 hp for the stated motor | Defines the motor size used by the control and protection functions. |
| Motor rated voltage | Motor nameplate and its actual connection | Must match the connected winding arrangement and drive output capability. |
| Motor rated current | Motor nameplate for the selected voltage connection | Provides the basis for motor overload protection. |
| Motor rated frequency | Motor nameplate | Defines the rated operating point. |
| Motor rated speed | Motor nameplate, if requested by the drive | Supports slip-related calculations and motor control. |
| Minimum and maximum frequency | Machine and motor limits | Restricts the potentiometer command to a safe operating range. |
| Acceleration and deceleration | Machine load, required cycle, and drive test results | Controls mechanical shock and determines stopping travel. |
The source describes one 0.75 hp motor, not three motors. If the installed drive actually feeds multiple motors, stop this setup and redesign the sizing and protection from each motor nameplate; a single motor-current entry does not provide individual overload protection.
Configure commands and speed reference from the manual
- Isolate power using the site electrical procedure and verify the drive is safe to work on before touching its terminals.
- Confirm that the drive input rating matches the supply and that its output rating covers the motor nameplate current. Stop if either comparison fails.
- Enter the verified motor nameplate data. Use the exact parameter names and allowed ranges in the
CX 2000manual. - Select terminal control as the run-command source.
- Select the documented three-wire mode if Forward Start, Reverse Start, and Stop are momentary push buttons. Map each digital input according to the drive’s wiring diagram; do not guess terminal numbers.
- Select the analog input as the frequency or speed-reference source. Wire the potentiometer only to the documented reference supply, analog input, and analog common. Read the required potentiometer resistance and reference voltage from the manual.
- Set minimum frequency, maximum frequency, acceleration, and deceleration from the machine limits. Start with the motor uncoupled or the mechanism in a safe test condition.
- For a one-revolution sequence, route the sensor to the external controller and let that controller issue mutually exclusive forward and reverse commands. Add a state that removes the forward command before reverse is allowed.
Never energize forward and reverse inputs together. The controller must inhibit the opposite direction until the active command is removed and the required stopping condition has been reached. Use the drive’s documented status output or measured machine feedback when the mechanism cannot tolerate reversal while moving.
Build the one-revolution sequence around feedback
A practical state sequence is IDLE, FORWARD, , REVERSE, and COMPLETE. On the cycle-start edge, command forward. Ignore a sensor already active at startup until it clears, then accept the next valid sensor edge as the completed forward revolution. Remove the run command, wait for the selected stop condition, command reverse, and stop on the corresponding return event.
Latch faults and timeouts in the external controller. If the sensor never changes state, the controller must remove the run command rather than leave the motor running indefinitely. Choose the timeout from measured maximum cycle time plus an engineering margin; no fixed value can be selected without the commanded speed, acceleration, load, and sensor location.
A potentiometer creates another decision: either let the operator change cycle speed or clamp the sequence to a validated range. At low speed, motor cooling and available torque may limit continuous operation. At high speed, stopping travel may pass the sensor target. Establish the usable range by test and restrict the analog command accordingly.
Verify the setup before returning it to service
- With run commands inactive, power the drive and confirm that it remains stopped.
- Check the potentiometer reading at minimum, midpoint, and maximum. Confirm that the displayed reference follows the knob in the correct direction and stays inside the configured limits.
- Jog or briefly run forward at low speed. Confirm actual shaft direction. Remove the command and verify Stop works.
- Test reverse at low speed only after forward motion has stopped. Confirm that command interlocking prevents simultaneous direction requests.
- Run the one-revolution cycle at minimum allowed speed, normal speed, and maximum allowed speed. Mark the start position and measure final-position error in both directions.
- Repeat under the highest expected mechanical load. Monitor drive current and diagnostic status; compare current with the motor nameplate and configured motor data.
- Interrupt the sensor, press Stop, and cycle control power during controlled tests. The machine must stop safely and must not restart merely because power returns.
If position varies with speed, correct the sensor placement, approach speed, deceleration, or stopping method. Changing motor data to hide overcurrent or improve stopping is the wrong fix; motor parameters describe the motor, while motion settings and external logic control the cycle.
FAQ
Can I program the L&T CX 2000 for exactly one motor revolution?
A standard speed-run command does not identify one revolution. Use a revolution or position sensor and external sequence logic unless the exact drive manual documents a suitable positioning function.
Can I use three momentary push buttons for forward, reverse, and stop?
Yes, when the drive is configured for its documented three-wire terminal-control mode. Assign the inputs from the CX 2000 manual and electrically or logically interlock Forward and Reverse.
Does the 0.75 hp motor rating give me every required parameter?
No. Enter rated voltage, rated current, rated frequency, rated speed, and any other requested motor data from the motor nameplate; rated current must correspond to the actual winding connection.
Can I connect a speed potentiometer directly to the drive?
Yes, if its resistance and wiring match the documented analog-input circuit. Connect it only to the specified reference supply, analog input, and analog common, then select that input as the speed-reference source.
Does the model number tell me the terminal and parameter numbers?
No. Stop here if the exact manual cannot be matched to LTVF-C40003BAA, if the supply or current rating does not match, or if the motor starts unexpectedly during testing. Contact official L&T support with the full drive identifiers, motor-nameplate data, supply measurements, wiring diagram, and displayed fault information before proceeding.