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Sprecher + Schuh
Motor Control + Protection consultants since 1903
Motor Control + Protection consultants since 1903


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Contactor Life Expectancy - The electrical life of switchgear is defined by the total number of possible operating cycles under operating conditions. When this number is reached, the wearing parts must be replaced or revised. Testing for electrical life expectancy is an expensive process, requiring precise measurements and actual components for testing. The manufacturer usually does testing and
publishes the data in technical specification guides. These numbers can vary widely from product to product, and application to application. What does this figure really mean to the plant or machine designer? How long is this contactor going to operate before routine repairs and down time make it a replacement cost? To determine this, two things are needed: the expected electrical life, and the expected service life. Read our new white paper to learn more.
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Get the inside story on phase failure protection. New White Paper just posted. #motorprotection
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Troubleshooting PCS Soft Starters

Problem: A PCS controller ramps the motor up to speed. At speed, the auxiliary contact closes. The PCS controller then stops the motor and restarts the motor continuously, and appears to pulse the motor. The red light stays on all of the time on the PCS soft starter. There are no faults on the PCS controller. Why does the PCS soft starter continually start and stop the motor?

Cause:The motor is not sized correctly for the PCS controller.

After the motor comes up to speed, the internal built-in bypass contactor closes and the PCS soft starter begins monitoring the phase current and voltage for faults. If the run-mode motor current is low, then it is difficult for the PCS soft starter to distinguish between low run-mode motor current and disconnected motor leads (motor leads are disconnected after the motor is up to speed). Instead of faulting for an open load, the PCS soft starter will attempt to restart the motor. If the motor is undersized for the PCS soft starter, the motor will continue to attempt re-start.

Solution: This re-start behavior will be exhibited using an undersized motor, i.e. a ¾ HP motor that draws less than 1 amp during running and using this motor with the PCS-009-600V controller. It is recommended that the correctly sized PCS controller be used for the motor FLA. The motor FLA should be within the minimum and maximum range shown on the PCS controller's front cover. In the case of the PCS-009-600V controller, the motor full load current range supported is between 3 and 9 amps.

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A Case of Mistaken Identity

We often get calls from customers in the field looking for a replacement reversing contactor for their elevator control. What these technicians don’t realize is a two contactor wye-delta assembly can easily be mistaken for a reversing contactor assembly and ordering the wrong unit can cause confusion, delays and headaches. Excluding any bus/jumper bars, the elevator wye-delta assembly and the reverser set-up both utilize the same components: (2) contactors & (1) mechanical interlock. With the same basic components, this is the reason someone might confuse an elevator wye-delta for a reversing contactor.

A reversing contactor (Series CAU) includes reversing power connection kits on both the line and load sides of the contactors.  A two contactor wye-delta assembly (Series CA7Y2) is equipped with a load side connector and only a shorting bar on the line side.

For additional information visit the Sprecher + Schuh ecatalog on Special Use Contactors or contact technical support.
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