Delta MS300 and VFD-EL Setup: Switching to Terminal Control Mode
Transferring the control of Delta variable frequency drives to external terminals is accomplished using two base parameters. For the compact VFD-EL series, these are parameters 02.00 (frequency source) and 02.01 (run command source), while for the advanced vector drive MS300 series, they are parameters 00.20 and 00.21. However, wiring mistakes on terminal strips, neglecting system grounding, or incorrect entry of motor nameplate values will frequently lead to overcurrent faults or motor windings overheating.
At chastotnik.ua, we help industrial engineers configure and wire frequency inverters for various automation tasks daily. To make your integration process straightforward, our lead engineer prepared this step-by-step technical guide containing verified register maps, wiring paths, and field-tested advice for programming Delta Electronics drives.
Power Terminals and Motor Connection Wiring
The power stage of VFD-EL and MS300 inverters features different terminal layouts for connecting a braking resistor, although the AC mains supply and motor cabling are wired identically. AC input power (either single-phase 220V or three-phase 380V, depending on the model rating) is always wired to the input terminals R/L1, S/L2, T/L3. The three-phase induction motor is connected to the output terminals U, V, and W (labeled as U/T1, V/T2, W/T3 on the VFD-EL series).
When wiring, observe these technical differences between the two drive families:
- Delta VFD-EL: This series lacks a built-in dynamic braking transistor (chopper). A braking resistor cannot be wired directly to the power terminals. To stop an inertial load quickly, you must install an external dynamic brake unit connected to the + and - terminals, and then wire the resistor to that brake module.
- Delta MS300: Features a built-in dynamic braking chopper on all models up to 22 kW inclusive. The braking resistor is wired directly to the +1/B1 and B2 terminals, reducing panel space requirements and simplifying assembly. Our stock contains a wide selection of dynamic braking resistors available in the accessories category.
Correct system grounding has a decisive role in eliminating electromagnetic interference. The PE ground terminal must be connected to the main ground busbar with an impedance below 10 Ohms using a dedicated copper grounding wire. Never mix the ACM analog common signal line with the PE power ground terminal, as doing so introduces electrical noise into the analog measurement circuits.
Motor Nameplate Parameters and Auto-Tuning Sequence
Before launching the motor under load for the first time, you must enter its exact nameplate parameters. This step enables proper electronic motor overload protection and enables accurate magnetic flux calculations in sensorless vector control mode.
Configure the following settings depending on your specific VFD series:
- Delta VFD-EL Configuration: Enter the motor rated current in parameter 07.00 (expressed as a percentage of the drive's rated output current). Since VFD-EL drives run primarily in scalar V/F mode, precise stator resistance values are not critical, but parameter 07.00 sets the trigger threshold for the oL motor overload fault.
- Delta MS300 Configuration: This drive supports high-performance sensorless vector control. The motor parameters are located in Group 05. Enter the motor rated current in 05.01 (Amps), rated power in 05.02 (kW), rated speed in 05.03 (RPM), pole count in 05.04 (e.g., enter 4 for a 1500 RPM motor, or 2 for a 3000 RPM motor), rated frequency in 05.05 (Hz), and rated voltage in 05.06 (V).
Once nameplate settings are entered, run the automatic motor identification routine (Auto-tuning). On the MS300 drive, select parameter 05.00. Setting this parameter to 1 triggers a dynamic auto-tune (requiring the motor to spin freely without load), while setting it to 2 runs a static auto-tune (used when the motor shaft is coupled to a pump or gearbox and cannot rotate). Press the RUN key on the digital keypad to start the routine. Upon completion, the drive calculates and saves stator resistance and inductance values directly into its internal memory.
Terminal Control Setup: Keypad PU to External Signals
By default, Delta drives ship configured for digital keypad control (PU mode). To switch to remote operation using external cabinet buttons, selector switches, or PLC dry contacts, the drive channels must be reprogrammed.
Adjust the following registers according to the drive model in use:
- On Delta VFD-EL: Set parameter 02.00 to 1 to receive the frequency reference from the AVI analog terminal (0-10V from an external potentiometer). Set parameter 02.01 to 1 to enable run commands from external terminals MI1 and MI2. The keypad STOP button remains active for safety overrides.
- On Delta MS300: Set parameter 00.20 to 1 to set the frequency source via the AI1 analog input terminal (0-10V). Change parameter 00.21 to 1 to assign the run command source to the external MI1/MI2 digital terminals.
Dry contacts are wired to activate run commands. Delta's factory digital logic uses an NPN configuration sinking current to the DCM common terminal. To run forward (FWD), connect the MI1 terminal to DCM. To run in reverse (REV), connect the MI2 terminal to DCM. If you require a PNP sourcing configuration (+24V active signal), flip the physical NPN/PNP switch on the drive control card to the PNP position, and connect the digital inputs to +24V instead of DCM.
Digital input terminal functions are programmable: MI1 is configured using parameter 05.01 on the VFD-EL, and parameter 02.01 on the MS300. The factory default value of 1 assigns the Forward/Stop function, which is perfect for most standard industrial applications.
Acceleration, Deceleration, and Braking Resistors
Acceleration and deceleration times determine how smoothly the drive ramps the motor speed, preventing overcurrent spikes and mechanical shock. Our field engineers adjust these parameters to fit the load characteristics.
The primary ramp parameters are structured as follows:
- For VFD-EL: Acceleration Time 1 is adjusted in parameter 01.09, and Deceleration Time 1 in 01.10. Both support a range of 0.1 to 600.0 seconds.
- For MS300: Acceleration Time 1 is set in parameter 01.12, and Deceleration Time 1 in 01.13. The MS300 series supports 4 separate acceleration/deceleration ramp profiles that can be switched dynamically using digital inputs.
For high-inertia mechanisms like heavy fans, blower units, or centrifuges, stopping the motor too fast forces the drive into a regenerative generator state, triggering an ov (overvoltage) fault on the DC bus. If increasing the deceleration time is not feasible due to process requirements, you must install a braking resistor. Connect the resistor to +1/B1 and B2 on the MS300 series. On VFD-EL, always use an external dynamic brake unit, as wiring a resistor directly to the VFD-EL power terminals will destroy the drive's output power modules.
Special Functions: Phase Loss Disabling and 1-Phase Capacitor-Free Motor Wiring Hack
Delta frequency inverters can handle custom wiring layouts, such as driving a three-phase motor on single-phase supply or running a single-phase induction motor without its starting capacitor. These methods require disabling phase loss protection.
To wire a single-phase capacitor-run motor directly to the drive without its capacitor, follow this procedure:
- Motor Connection: Remove the run and start capacitors from the motor terminal box. Identify the main (run) and auxiliary (start) windings. Connect the main winding to the U and V output terminals of the drive. Connect the auxiliary winding to the U and W output terminals.
- Disabling Drive Fault Protections: Since VFDs expect a symmetrical three-phase load, the drive will trigger an output phase loss (oPF) fault upon startup. To bypass this protection, set parameter 06.01 to 0 (Output Phase Loss Protection Disabled). Also, if operating the drive on a single-phase 220V power supply, disable input phase loss protection by setting parameter 06.00 to 0.
Our field experience indicates that this operating mode requires monitoring motor temperature. Because current flowing through the single-phase motor windings is asymmetrical, the drive's electronic thermal protection cannot accurately model motor heating. We suggest installing an external motor protection relay or using standard three-phase motors, which offer higher efficiency and unmatched reliability. Explore all motor and drive options on our main website at chastotnik.ua.
Delta MS300 and VFD-EL Parameter Comparison Table
This comparative guide allows engineers to quickly map parameters when migrating from the legacy VFD-EL series to the modern MS300 series:
| Control Function | Delta VFD-EL Parameter | Delta MS300 Parameter | Recommended Configuration Values |
|---|---|---|---|
| Frequency Command Source | 02.00 | 00.20 | 1 — external analog input AVI/AI1; 3 or 4 — digital keypad potentiometer |
| Run Command Source | 02.01 | 00.21 | 0 — digital keypad keys; 1 — external digital terminal strip |
| Acceleration Time 1 (sec) | 01.09 | 01.12 | Application dependent (typically ranges from 5.0 to 15.0 sec) |
| Deceleration Time 1 (sec) | 01.10 | 01.13 | Application dependent (typically ranges from 5.0 to 20.0 sec) |
| Motor Rated Current | 07.00 | 05.01 | Nameplate rated motor current (Amps for MS300, percentage for VFD-EL) |
| Motor Rated Frequency (Hz) | 01.01 | 05.05 | Base motor frequency from nameplate (typically set to 50.0 Hz) |
| Motor Rated Voltage (V) | 01.02 | 05.06 | Nameplate operating voltage (220V for delta, 380V for star connection) |
| MI1 Input Terminal Logic | 05.01 | 02.01 | Set to 1 — Forward / Stop function (FWD/STOP) |
| Input Phase Loss Protection | 06.00 | 06.00 | 0 — disabled (useful for single-phase mains); 1 — enabled |
| Output Phase Loss Protection | 06.01 | 06.01 | 0 — disabled (required for single-phase motor hack); 1 — enabled |
Troubleshooting Common Faults (oc, ov, uF, oL)
Variable frequency drive operation can sometimes trigger protective trips. Most faults stem from configuration issues and can be resolved in the field without sending the unit to a service center.
Review the primary fault codes and diagnostic remedies below:
- oc Fault (Overcurrent): Output current exceeded the drive's safety threshold. If this occurs during acceleration, increase the ramp time in parameter 01.09 (VFD-EL) or 01.12 (MS300). Verify that the motor rated current parameters match the nameplate. Inspect output cabling for phase-to-phase or phase-to-ground short circuits.
- ov Fault (Overvoltage): The DC bus voltage rose too high due to regenerative energy from the motor during deceleration. Increase the deceleration ramp time in 01.10 (VFD-EL) / 01.13 (MS300) or connect a dynamic braking resistor.
- uF or Lu Fault (Undervoltage): The incoming AC mains voltage dropped below the minimum operating limit. Check the AC voltage across terminals R/L1, S/L2, and T/L3 under load. Undervoltage trips are often caused by undersized power cables or a weak local electrical grid.
- oL Fault (Overload): The electronic thermal overload circuit detected sustained excessive motor current. Inspect the driven equipment for mechanical binding or lockups. Running a motor at low frequencies (below 25 Hz) under high load reduces its internal fan's cooling capacity. In such cases, fit an independent external cooling fan to prevent overheating.
Frequently Asked Questions
What braking resistor resistance is required for Delta MS300 series?
The minimum allowable braking resistance is strictly defined in the manufacturer's manual for each specific VFD power rating. For instance, a 1.5 kW 380V MS300 model requires a minimum resistance of 250 Ohms and a continuous power rating of at least 80W. Connecting a braking resistor with resistance below the specified limit will damage the drive's built-in dynamic braking transistor.
How do I reset a Delta variable frequency drive to factory defaults?
To perform a complete parameter reset to factory defaults, use parameter 00.02. To restore parameters tailored for a European 50Hz electrical system, set 00.02 to 9. For a 60Hz system, set 00.02 to 10. After setting this parameter, disconnect the input power for 2-3 minutes to allow the processor to cycle down completely.
How do I enable motor reversing when operating from external terminals?
To enable reversing, connect a switch to the MI2 digital input and the DCM common terminal (when using NPN sink logic). Verify that parameter 02.02 (on MS300) or 05.02 (on VFD-EL) is set to 2 (factory default for REV operation). Ensure that reverse operation is not disabled in parameter 01.11, which must be set to 0 (reverse enabled).
Can I run two motors simultaneously from a single Delta VFD?
Yes, wiring multiple motors to a single drive is allowed, but only when running in scalar V/F control mode (vector control is not supported for multi-motor layouts). The combined rated current of all connected motors must not exceed the rated output current of the drive. Also, each motor must be protected by an individual thermal overload relay.
Why does my Delta drive trip on oL fault during pump startup?
The oL trip indicates a motor overload condition. Centrifugal pumps exhibit a quadratic relationship between speed and torque. If the operating conditions force the pump to move high-density fluid, the motor current rises above the rated threshold. Check parameter 07.00 (VFD-EL) or Group 05 (MS300) to ensure they are configured to match the motor nameplate.
Conclusion and Sizing Delta Equipment from Stock
Configuring Delta MS300 and VFD-EL drives according to their nameplate values ensures long-term and stable motor performance. Transitioning from keypad control to external terminals is a standard stage in building reliable electrical panels. By utilizing the parameter maps provided in this guide, you can quickly integrate these drives without reading through massive instruction manuals.
At chastotnik.ua, we maintain a permanent inventory of Delta Electronics variable frequency drives in Ukraine. Our technical support team is ready to assist you in selecting the perfect drive for your specific application. Visit our main store catalog to check live prices and purchase a genuine Delta frequency inverter with an official factory warranty. You can also view all available options in our broad frequency converters category to compare single-phase and three-phase models.
