Mike Dolt Enterprises Logo Mike Dolt Enterprises

Topic: 480V-3ph Motor connections to VFD Inverter

User: Rob2025, Location: Toronto, Canada

Asked on: Wednesday, July 16, 2025 at 10:26 pm EDT
Answered on: Wednesday, July 16, 2025 at 10:26 pm EDT

Question: HiI would like to learn more on 400V-3ph Motor connections to VFD driver.In general, I found there are only 3 connections U, V, W available on VFD Inverter terminals for the motor. If there are only 3 wires connected from VFD to the motor and as there is no Neutral terminal available from VFD, then does it mean Motor is always connected in a Delta configuration?Is there any way we connect the motor in Wye or Star configuration to VFD?

You're on the right track! Let's break down the connections and configurations of 400V 3-phase motors with VFDs

Understanding the Basics
VFDs and 3-Phase Power

Variable Frequency Drives (VFDs) output a
balanced 3-phase voltage to control the motor speed. They don't inherently require or provide a neutral connection.

Motor Windings

3-phase motors have three sets of windings. The way you connect these windings internally (or externally at the terminal box) determines whether the motor is configured in Delta or Star (Wye).

Terminal Markings

The terminals on the motor are typically labeled U (or T1), V (or T2), and W (or T3). Sometimes you'll see additional markings like X, Y, and Z, or numbers (1-6 or 1-9) to indicate the individual winding ends.

Delta vs. Star (Wye) Connection and VFDs
VFDs Don't Dictate the Internal Motor Configuration

The VFD provides the 3-phase power; it doesn't force the motor to be in Delta or Star. The motor already has an internal (or externally configurable) winding arrangement.

Connecting a Delta Motor to a VFD

Yes, you can connect a motor configured in a Delta formation to the VFD. The VFD just provides the 3-phase power needed for the motor to run. The U, V, and W terminals of the VFD connect directly to the corresponding terminals of the Delta-connected motor.

Connecting a Star (Wye) Motor to a VFD



Absolutely!
You can also connect a motor configured in a Star (Wye) configuration to a VFD. Again, the VFD simply provides the 3-phase power. The U, V, and W terminals of the VFD connect to the appropriate terminals of the Star-connected motor.

How the Configuration is Determined

The Delta or Star configuration is determined by how the motor windings are connected inside the motor terminal box (or, less commonly, internally within the motor itself). Here's the key: Externally Configurable Motors

Many 3-phase motors (especially those designed for multiple voltage ratings, like 230/400V) have a terminal box with multiple terminals (usually six). You use
external jumpers or links to connect these terminals in either a Delta or Star (Wye) configuration.

Delta Connection

You'll connect winding ends in a triangle/Delta shape using the jumpers.

Star (Wye) Connection

You'll connect one end of each winding together at a central point (the "star point"), and the other ends become your U, V, and W terminals.


Internally Configured Motors

Some motors are internally wired in either Delta or Star. In this case, you only have three terminals (U, V, W) available in the terminal box, and you can't change the configuration.

Important Considerations
1. Voltage Rating

The most crucial factor is matching the motor's voltage rating to the supply voltage based on the connection type.

Star (Wye) Connection

The voltage rating on the motor nameplate refers to the line-to-line voltage. For example, a 400V Star-connected motor is designed to be used with a 400V 3-phase supply.


Delta Connection

The voltage rating on the motor nameplate refers to the line-to-line voltage. For example, a 400V Delta-connected motor is designed to be used with a 400V 3-phase supply.

Dual Voltage Motors (e.g., 230/400V)

These motors are designed to be connected in Delta for the lower voltage (e.g., 230V) and in Star (Wye) for the higher voltage (e.g., 400V). This is because the voltage across each winding is the same regardless of whether it's connected in Delta or Star2.

Nameplate Information

Always,
always refer to the motor's nameplate! It will tell you: The voltage rating(s) of the motor. The proper connection type (Delta or Star) for each voltage rating. The rated current.3.

Starting Torque and Current

Delta and Star configurations affect the starting torque and current characteristics of the motor. Star connections generally have lower starting torque and lower starting current compared to Delta connections. However, VFDs mitigate this issue because they can control the voltage and frequency applied to the motor, allowing for soft starts and controlled acceleration, regardless of the motor configuration.4.

VFD Parameters

You might need to adjust VFD parameters based on the motor's voltage, current, and horsepower rating. You absolutely need to input the motor's rated voltage and current into the VFD for proper operation and protection.

Example Scenario

Let's say you have a motor with a nameplate that reads "230V Delta / 400V Star (Y)".

For a 400V 3-phase supply

You would connect the motor in a Star (Wye) configuration, using the jumpers in the terminal box as specified in the motor's documentation. You would then connect the VFD's U, V, and W outputs to the corresponding motor terminals. In the VFD setup, you would need to program the motor's voltage as 400V, its rated current (from the nameplate), and its horsepower.


For a 230V 3-phase supply

You would connect the motor in a Delta configuration, using the jumpers as specified. You would then connect the VFD's U, V, and W outputs to the corresponding motor terminals. In the VFD setup, you would need to program the motor's voltage as 230V, its rated current (from the nameplate for the Delta connection), and its horsepower.

In Summary


The VFD provides the 3-phase power to the motor. The motor's internal winding configuration (Delta or Star) is independent of the VFD. The connection type is determined by the motor's design and voltage rating, and you may be able to configure it using jumpers in the terminal box. Always match the motor's voltage rating (based on the connection type) to the supply voltage and program the appropriate parameters into the VFD. Flag for review

Previous Question View on the official Mike Holt Forum Next Question