Electrical MaintenanceMotor Starters

Motor Starters

SKU: RVCT-588
Duration: 0.25 Hrs

When a relay is used to switch a large amount of electrical power through its contacts, it is designated by a special name: contactor or starter. This course covers contactors, incoming and auxiliary contacts, overload heaters, starter construction, starter operation, using heater elements in troubleshooting, and typical starter configurations.

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Course Details

Specs

Course Level Intermediate
Languages English
Compatibility Audio, Video
Based on: Industry Standards and Best Practices

Vector Solutions

Author

With over two decades of experience designing advanced 3D animated courseware and developing our proprietary learning management software, we pride ourselves by having developed over 1,000 safety and operations training modules, which have helped train over 250,000 workers worldwide. Our highly experienced team provides the industry with a simple and high-quality means of training their workforce. Whether your team consists of 25 people or an enterprise with thousands, we’re here to help.

Key Questions

What is a contactor?
A contactor is a multi-contact switch, often activated electromagnetically, designed to start and stop large electric currents at high voltages.

What is the difference between circuit breakers and overload protection devices?
Circuit breakers operate by stopping power in very high overcurrent situations such as those that would occur from a short circuit or a ground fault. An overload protection device is meant to protect a motor from operating for prolonged periods of time at a current that is moderately above full load amperage.

How does a bimetallic overload protection device work?
Bimetallic strips bend when heated. In an overload device, a small heater is wired in series with a motor winding. If excessive current flows through the heater, it causes the strip to bend sufficiently to open the contacts that supply power to the motor winding.

What are some types of alternative starters that are available?
A typical starter is an electromechanical starter which connects all motor windings simultaneously. This is called an across-the-line starter. More complex starter systems allow for reversal of the motor, multi-speed starts and reduced voltage starts.

What are the advantages of a solid-state starter over an electromagnetic starter?
Solid-state starters offer faster switching, the elimination of mechanical contacts and pitting, and the ability to more precisely control the voltage applied during startup.

Sample Video Transcript

Note that there are two electrical circuits in a contactor, one is the control circuit connected to the coil that typically runs at a lower voltage, such as 24 or 120 volts. The second circuit is the primary power circuit that connects the power lines to the motor through the contactor contacts. As mentioned earlier, the contactor closes or opens all three power lines simultaneously when the coil moves the core. The contactor also simultaneously activates auxiliary contacts which can be used for control purposes and for contactor status reporting.

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