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Three-Point Starter vs. Four-Point Starter: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 12, 2024
A three-point starter uses three points of contact for starting motors, regulating current, while a four-point starter adds an extra point for better voltage regulation.

Key Differences

A three-point starter, used in DC motors, includes three contacts: armature, field, and line. In contrast, a four-point starter has an additional point, typically for a stabilizing resistor, which adds an extra layer of protection against voltage fluctuations. This additional point in four-point starters provides better control and stability compared to three-point starters.
In a three-point starter, the voltage and current are controlled through the armature, field, and line contacts, making it simpler but less adaptable to voltage variations. The four-point starter, with its extra contact, offers improved handling of voltage variations, ensuring more consistent motor performance. This makes four-point starters more suitable for applications with fluctuating supply voltages.
The three-point starter’s design can lead to field weakening if there's a significant drop in supply voltage, potentially causing the motor to over-speed. The four-point starter mitigates this risk with its additional point, maintaining more consistent field current irrespective of supply voltage variations. This characteristic makes four-point starters safer for motors in unstable voltage conditions.
Three-point starters are generally more compact and less complex, making them easier to maintain and more cost-effective for stable environments. Four-point starters, while slightly more complex, offer better protection and performance in systems where voltage stability is a concern, justifying their additional complexity and cost.
The choice between a three-point and a four-point starter often depends on the application's voltage stability and the motor's size. While three-point starters are adequate for smaller motors with consistent voltage, four-point starters are preferable for larger motors or in environments with voltage fluctuations.

Comparison Chart

Contact Points

Three: armature, field, line.
Four: armature, field, line, additional stabilizing point.

Voltage Regulation

Less adaptable to voltage variations.
Better handling of voltage fluctuations.

Risk of Over-Speeding

Higher in unstable voltage conditions.
Reduced due to consistent field current.

Complexity and Cost

More simple and cost-effective.
Slightly more complex and costly.

Ideal Application

Suitable for smaller motors, stable voltage.
Preferred for larger motors, fluctuating voltage.

Three-Point Starter and Four-Point Starter Definitions

Three-Point Starter

It's simpler and more cost-effective than four-point starters.
For cost efficiency, we chose a three-point starter for our motor.

Four-Point Starter

It offers better voltage regulation compared to three-point starters.
Voltage fluctuations were no longer an issue after switching to the four-point starter.

Three-Point Starter

A three-point starter is a device for starting and regulating DC motors with three connections.
The three-point starter is perfect for our small DC motor due to its simplicity.

Four-Point Starter

This starter reduces the risk of motor over-speeding in variable voltage conditions.
The four-point starter ensures consistent speed despite power variations.

Three-Point Starter

Three-point starters are suitable for small motors with stable voltage.
Our workshop uses a three-point starter for reliable motor operation.

Four-Point Starter

A four-point starter is a device for starting DC motors, adding an extra stabilizing contact.
The four-point starter was installed to handle the fluctuating power supply in our factory.

Three-Point Starter

This starter can be more vulnerable to voltage drops.
The motor experienced over-speed due to a voltage drop, indicating the limits of the three-point starter.

Four-Point Starter

Suitable for larger motors or systems with voltage instability.
For our high-capacity motors, the four-point starter provides the necessary stability.

Three-Point Starter

It connects armature, field, and line for controlling motor start-up.
The armature reaction is efficiently managed by the three-point starter in the motor.

Four-Point Starter

More complex in design, offering enhanced protection.
The added complexity of the four-point starter is a small price for enhanced motor safety.


What is a three-point starter?

A three-point starter is a device used for starting and controlling DC motors, with three main connections.

What is a four-point starter?

A four-point starter is similar but includes an additional point for better voltage stabilization in DC motors.

Why choose a three-point starter?

Choose a three-point starter for smaller motors or when voltage supply is stable and consistent.

In what situation is a four-point starter preferred?

A four-point starter is preferred for larger motors or where the voltage supply is variable and less stable.

What are the risks of using a three-point starter in fluctuating voltage?

It can lead to motor over-speeding and potential damage due to voltage drops.

Do both starters work with AC motors?

No, they are specifically designed for DC motors.

Is installation of a four-point starter more complex?

Yes, due to the additional stabilizing contact, it's slightly more complex.

Can I replace a three-point starter with a four-point starter?

Yes, if the motor and system requirements indicate a need for better voltage stabilization.

Does the extra point in a four-point starter consume more power?

No, the extra point is for stabilization and doesn't significantly affect power consumption.

Can a three-point starter handle large industrial motors?

It's not recommended, especially if the motor is subject to variable voltage conditions.

What is the primary benefit of a three-point starter?

Its simplicity and cost-effectiveness for smaller, stable applications.

How does a four-point starter enhance motor safety?

It maintains consistent voltage and current, reducing risks like over-speeding in fluctuating voltage conditions.

How does the four-point starter protect against voltage fluctuations?

By providing a more stable current to the motor, irrespective of supply voltage variations.

Can I use a three-point starter in an unstable power supply environment?

It's not advisable due to potential risks like over-speeding and inefficiency.

Is maintenance of a four-point starter more demanding?

Slightly more, due to its additional components and complexity.

Are there cost differences between the two starters?

Generally, four-point starters are more expensive due to their additional features.

Are these starters compatible with all DC motors?

Compatibility depends on the motor's size and voltage characteristics.

How do I know which starter is right for my motor?

Consider the motor size, voltage stability, and operational demands to determine the suitable starter.

Can either starter be used in residential applications?

These starters are typically for industrial or larger-scale applications, not common in residential settings.

What is the key advantage of the four-point starter in industrial settings?

Its ability to handle larger loads and provide stable operation in fluctuating power conditions.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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