How Magnetic Motor Starter Works

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Most people don’t have a technical know-how about the electrical components our machines have, particularly to those which are not visible or run inside the machine like a magnetic motor starter. Have you ever asked the question “how does magnetic starter works?”


magnetic motor starter is an electromagnetically operated switch that protects your electric motor during start up. It can accommodate heavy-duty loads such as 3 phase large motors and other industrial machineries. Magnetic motor starters provide under-voltage and overload protection and an automatic cut off in the event of a power failure. Another purpose of magnetic motor starter is to protect a motor that has no thermal overload protection in the motor itself. MOTOR-STARTER-2-300x277 A magnetic motor starter is a combination of a contactor and an overload relay, which will open the control voltage to the starter coil if it detects an overload from your motors during usage. The thermal type uses a device installed on the overload relay called a “heater”. This is a bi-metal element that each leg of the motor goes through. A magnetic motor starter comes in different ratings based on the full load amperage of the motor. While your machine is running, the current flows through the heater.  If the current draw of the motor exceeds the rating of the heater, the heater element heats up and causes the relay to “trip” which interrupts the contactor coil circuit and de-energizes the contactor. Here are the two types of magnetic motor starters which Meiji carries:

  1. Full-Voltage (across-the-line) Magnetic Motor Starter

Magnetic motor starters are commonly available as full-voltage (across-the-line), reduced-voltage, and reversing. A full-voltage or across-the-line magnetic motor starter applies full voltage to the motor, which means it is designed to properly handle the levels of in rush current that will develop as the motor is started. Reduced-voltage starters are designed to limit the effects of inrush current during motor start up. These are available in electro-mechanical and electronic formats.

  1. Full-Voltage Reversing Starter

Reversing starters are designed to reverse shaft rotation of a three-phase motor. This is accomplished by interchanging any two-line conductors that supply the motor load. The reversing magnetic motor starter features a forward and a reverse starter as part of the assembly. Electrical and mechanical interlocks are provided to ensure only the forward or the reverse starter can be engaged at any given time, but not at the same time. Magnetic motor starters are usually used in woodworking machinery such as cabinet saws or shapers. Machines with smaller loads, such as a drill press or most handheld tools normally use only a switch instead. Magnetic starters are stock components for many machines, and aftermarket starters are also available for use as replacements or for retrofitting older machines.

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“National Fire protection Association (NFPA) a U.S. trade association, states that all machinery requires a magnetic starter to protect against unintentional restarting of a machine in cases of restoration of voltage.” – NFPA 79 standard 7.5.3, Wikipedia.

Meiji Electric carries high quality LS Magnetic Motor Starters. You have the option to enclose your motor starter or have it as is. Meiji Supplies magnetic motor starters from 1/8HP to 300HP. Full Voltage Non Reversing and Reversible Starters, Reduced Voltage Magnetic Starters in particular Wye Delta Motor Starters ranges from 7 1/2HP to 215HP for both 220 and 440 line voltage are also available with control voltages in accordance with customers’ needs.

Make a good start for your machines with Meiji Electric!

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