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Starter Motor Magnets

What is a Starter Motor?

A starter motor is an electric motor that turns the combustion engine in a car or some other vehicle so that it sucks fuel and air into the cylinders, compresses it, and starts working.

The starter motor draws electric current from the battery when you turn the key on the ignition. When the armature spins, the shaft, carrying a small gear wheel, engages with the engine flywheel to turn it over, kickstarting the combustion process. It is important to note that there is a difference between a starter motor and a motor starter. What we’ve described above is a starter motor.

What is a Motor Starter?

A motor starter, or magnetic starter, is a device powered by electromagnetism functioning as an initiating mechanism for electric motors and other high-current pieces of machinery such as cabinet saws or shapers.

What a motor starter does is function as the switch in electric motors. It helps to start, stop, and reverse the direction of a connected motor load using either manual or automatic controls.

A motor starter’s two main components often work together to control and protect the motor from current overload and other potential harms.

  1. Overload protection circuit: The primary function of this unit is to protect the motor from any harm arising from current overload issues. The overload protection circuit is essential in a motor starter because some engines use massive electrical currents. Therefore, when a vast current passes through the rotor, there is a high chance that the heavy electrical current will damage the winding and other appliances connected to the supply.
  1. Electrical Contactor: What this component does is simple and yet significant – It controls the ON/OFF feature of a motor.

So, a starter motor starts a combustion engine, while a motor starter starts an electric motor. However, the starter motor itself is an electric motor that draws power from the vehicle’s battery, and it has a motor starter that puts it on and off.

Functions of a Starter Motor

For an engine to run, it must turn over in cycles. And since it cannot rotate on its own, it needs something to give it the first push. That’s the job of the starter.

The starter motor replaced the pull string or recoil starter, which requires a rope and flywheel to start an engine. While the recoil starter remains a part of small engines like the lawn mower, chain saws, and portable generators, it cannot be found on luxurious machines. Every elegant machine, especially the ones required for human transportation, uses either a key or a push-to-start ignition system.

Types of Starter Motors

There are about seven types of starter motors on the market, but we will be focussing on two of them. They are:

Permanent Magnet Gear Reduction (PMGR) Starter

Gear reduction starters are not new to the automotive industry. In fact, they date as far back as the early 1960s as they were used in Chrysler products and several muscle cars. However, sometime in 1993, General Motors and Ford started producing a new breed of starters which were smaller, lighter, and more efficient than the starters on the market.

The only difference in these new starters is that they use permanent magnets instead of heavy and bulky electrical field windings which worked as electromagnets in the older generation of gear reduction starters. With the introduction of permanent magnets to the production of starters, the field windings were no longer necessary. One of the significant advantages of this development is the reduction in size and weight of the starters. They also produce greater torque during ignition and sound better than their predecessors.

In recent times, permanent magnet gear reduction starters are not only replacing their predecessors, but they are also replacing permanent magnet direct drive starters.

Permanent Magnet Direct Drive (PMDD) Starter

The direct drive starter was the long-used starter motor in automobiles before Chrysler invented the gear reduction starter. It was created in 1911 by the notorious inventor Charles Kettering. At the time, Kettering worked with Dayton Engineering Laboratories Company (DELCO) as the lead researcher. General Motors later acquired DELCO and made Kettering an executive member.

There are several differences between the direct drive starter and the gear reduction starter. The most prominent ones, however, are that direct drives required a lot of electrical power to crank an engine and, even at that, were slow. Also, to make DD starters more efficient and powerful, they had to have larger field coils. The arrival of the gear reduction starter solved these problems as it was faster and much smaller. It also required about 50% less electrical charge to crank an engine.

As technology advanced, the electrical windings in traditional gear reduction and direct drive starters were replaced with permanent magnets. The newer models with permanent magnets improved significantly in performance and size compared to the older models with electrical windings.

Components of a Starter Motor

Several parts make up a starter motor and help it function properly. If one or more of these components becomes faulty, the starter coil may malfunction or remain completely dysfunctional. Either way, it won’t have the capacity to crank an engine and start an automobile. We consider these components below.


The armature is an electromagnet that generates a magnetic field of opposing poles to the field coils or stationary permanent magnets. This opposition in their poles makes the armature spin when the starter is engaged.


The function of the commutator is to supply electric current to the armature, and it periodically reverses the direction of the armature’s electric current in the brush zones. This action interchanges the magnetic poles between the armature’s two surfaces.


The brushes, also known as carbon brushes, are usually 3. They conduct the current flowing from the battery unto the commutator, which then supplies the armature.


The solenoid is the switch that connects and disconnects the starter from the vehicle’s battery. Since the starter is an electrical motor, the solenoid is the motor starter that puts it on and off.


The plunger bears the lever and serves as the actuating arm that moves the pinion back and forth. When you turn the ignition key to start your car, the plunger moves forward, pushing the lever to engage the pinion with the ring gear in the flywheel. Once the engine turns over and rotates on its own, the plunger moves backward to disengage the pinion.

Lever Fork

The lever bears the pinion. When the plunger moves forward, it pushes the lever, plunging the starter gear, also known as pinion, into the engine to engage with the flexplate or flywheel.


The pinion is a small gear wheel that engages with the ring wheel in the flywheel attached to the engine when the armature begins spinning. When the pinion rotates, it spins the flywheel, turning the engine and starting the combustion process.

Field Coils/Permanent Magnets

Before manufacturers started using permanent magnets in starter motors, it was field coils, also called field windings. These are winding wires that function as electromagnets. When they receive an electrical charge from the battery, they generate a magnetic field that turns the armature and sets the ignition process in motion. In new models of starters, permanent magnets have replaced field coils because of their ability to generate more powerful and consistent magnetic fields. They also require a little electrical charge.

How Long Will a Permanent Magnet Starter Motor Last?

Permanent magnet motors use neodymium iron boron magnets. Neodymium magnets are the strongest available on the market and have high resistance to demagnetization forces. Theoretically, a permanent magnet should lose no more than 1% of its magnetic strength over a period of 100years, provided it is adequately maintained. However, note that the magnet is not the only component in the starter. So while the magnet in the starter may be perfectly okay, other parts may develop faults.

What are the Advantages of Permanent Magnet Starters?

Permanent magnet starters have numerous advantages:

  1. They are not expensive.
  2. Using permanent magnets increases efficiency.
  3. They don’t cost a lot to procure.
  4. They are far better than electromagnetic starter motors.
  5. They don’t require field winding.

What are the Applications of Starter Motors?

Starter motors have found applications in a wide range of products. Basically, any equipment with a key ignition system and a combustion engine will have a starter motor. Some machines use the key ignition but run on electric motors instead of combustion engines–electric vehicles fall in this category. On the other hand, some machines have combustion engines but use different ignition methods, such as rope start–lawn mowers, and most generators fall into this category.

  • Starter motors are used in many machines, including:
  • Cars.
  • Lorries.
  • Speed boats.
  • Buses.
  • Trucks, and more.

Which Permanent Magnet is Used in Starter Motors?

Neodymium magnets are used in starter motors, and this is because of the same reasons they are used in electric motors–their properties and characteristics. We discuss them below.

  1. Powerful Magnetic Fields: Neodymium’s strong magnetic field is one reason they are perfect for starter motors. It’s estimated that neodymium magnets produce magnetic fields of up to 1.4 teslas, while ceramic magnets can produce magnetic fields of just 0.5 – 1 teslas. This strong magnetic field is a testament to the neodymium magnets’ strength.
  1. High Resistance to Heat: Heat is one of the major demagnetization forces. Since neodymium magnets have high resistance to heat, they are guaranteed to last long in the motor without suffering any magnetic loss.
  1. High Coercivity: Coercivity is the ability of a magnet to resist demagnetization, including heat. Neodymium magnets’ high coercivity means they won’t lose magnetism even if the starter hits the ground forcefully or gets very hot due to overheating from the engine.
  1. Excellent Performance Even in Small Sizes: It has been observed that motors that contain permanent magnets perform better than any other motors of the same size. It is because of the sheer strength of the neodymium magnets in them. These magnets can generate magnetic fields and force more consistently than an electromagnet.


Presently, neodymium magnets are the most commonly used magnets in starter motors. It is due to their power and the strength of the magnetic fields they generate. As such, most of the starter motors in high-power machines use neodymium magnets.

If you are a researcher or a company looking to purchase high-quality neodymium magnets to manufacture starter motors, ROBO Magnetic is your best bet. We are one of the top manufacturers of durable neo magnets that perform excellently in their applications.

ROBO Magnetic is internationally recognized, and we have professionally trained experts who use the latest technology to manufacture our magnets. To order, you only need to provide the dimensions, shapes, and grades of the neodymium magnets you want, and we will manufacture and deliver them to you without delay. Contact us for further information.


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ROBO Magnetic Product Team

We are the manufacturer with 16 years of experience in custom neodymium magnets.

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