How to Provide Control, Isolation, and Protection for Motors Using Contactors

If you need reliable motor control, consider the Schneider Electric Easy TeSys family of contactors, overload relays, and manual motor starters. If you are not familiar with these devices, contactors are a special class of motor control relays designed to turn motors on and off using isolated control voltages. They are used in applications that include heating, ventilation, and air conditioning, as well as compressors, pumps, furnaces, material handling, packaging, and many related applications. Key features include rugged construction and larger, more robust contacts than standard electromagnetic relays (EMRs). They employ arc suppression techniques, including special materials and faster contact closure and opening.

The TeSys contactors from Schneider are compact components that are available in a broad range of power ratings and are easy to install (Figure 1). They conform to IEC, UL, and CSA standards. They also have UL and CSA product certifications and are IP-20 finger safe.

Figure 1: The Easy TeSys contactors are compact components that provide vital control and protection for motors in HVAC, compressors, pumps, furnaces, material handling, packaging, and many related applications. (Image source: Schneider Electric)

The Schneider Electric Easy TeSys DPE series three-phase contactors are available to control motors with power ratings of from 1/3 to 25 horsepower (HP), and isolated control voltages of 24 volts direct current (VDC), 24 volts alternating current (VAC), 120 VAC, and 240 VAC (Figure 2).

Figure 2 : The range of DPE series motor contactors are designed for an operational life of up to one million electrical cycles and are suitable for IEC 60947 utilization categories of AC-1, AC-3, AC-4, AC-8a, and AC-8b. (Image source: Schneider Electric)

As an example, the Schneider Electric DPE18U7 contactor will control a three-phase 7.5 HP motor at 480 volts and has a 240 VAC (U7) control voltage.

Thermal overload relays

The Easy TeSys family also includes a series of complementary thermal overload relays designed to protect AC circuits and motors against overload, phase failures, extended starting times, and stalled rotor conditions. The DPER series three-pole thermal-magnetic circuit breakers conform to IEC 60947-2 and IEC 60947-4-1 standards. They monitor the motor current, and if the current exceeds the current limit setting, the contacts open and stop the motor. There are fifteen different DPER models, each with a range of settable thermal current trip levels. The overload protection models are compatible with selected EASY TeSys DPE series contactors.

They connect directly to the bottom terminals of three-phase contactors DPE09 to DPE38 using the contactor’s screw clamp terminals. This is a feature I like due to the simplified wiring. The combination has a common width of 45 millimeters (mm) and can be mounted on a DIN rail or screwed to a panel using the DPE contactor mount (Figure 3).

Figure 3: The DPER thermal overload relays connect directly to the DPE series contactor. They offer a front-panel limit-setting dial with a sealable cover and an automatic or manual reset. Additionally, stop and reset buttons along with a test function on the front panel, allow for control and troubleshooting. (Image source: Schneider Electric))

The Schneider Electric Easy TeSys DPER32 thermal overload relay is a tripping class 10 overload protector with an adjustable trip range from 23 to 32 amperes (A). It is suitable for a 15 kilowatt (kW) motor operating at 400 volts. It is a differential device for operation with three-phase motors which also monitors for phase failure and load unbalance. This protector family is certified under multiple standards, including IEC, UL, and CUL.

Manual motor controllers/protector

The Easy TeSys family includes manual motor controllers that are designed to control as well as protect motors. The GP2E series of manual motor controllers conform to UL 60947-4-1 and are suitably rated for motor disconnect (Figure 4). The series combines motor control with both thermal and magnetic current overload protection. Pushbutton start and stop controls, and user-selectable thermal current limits are accessible via the front panel.

Figure 4: The Easy TeSys GP2E series combines motor control with both thermal and magnetic current overload protection. Pushbutton start and stop controls, and user-selectable thermal current limits are accessible via the front panel. (Image source: Schneider Electric)

Like the DPER overload relays, the GP2E controllers are thermal trip 10 rated devices. Combined with an Easy TeSys contactor, they can handle up to 35 kiloamperes (kA). There are fifteen products in the GP2E series, each with a specific range of thermal trip levels and fixed magnetic trip currents (Figure 5).

Figure 5 : In addition to motor control, the GP2E series controllers include adjustable thermal overload trip-level protection and fixed trip-level magnetic short-circuit protection. (Image source: Schneider Electric)

The Schneider Electric Easy TeSys GP2E14 is an example of a manual motor controller with an adjustable thermal trip rating of 6 to 10 A and a magnetic trip current of 138 A. It conforms to IEC 60947-2 and IEC 60947-4-1 standards.

Like the contactors, these manual motor controllers are easily mounted on a DIN rail or directly to the panel. A feature I like is the ability to combine the controller directly with a DPE contactor using a GV2AF3 combination block (Figure 6).

Figure 6 : The GV2AF3 enables the DPE series contactor to be mounted on the load side of the GP2E series manual motor controller. (Image source: Schneider Electric)

Conclusion

Schneider Electric’s Easy TeSys GP2E manual motor controllers, together with the company’s DPER thermal overload relays and three-pole DPE contactors, are designed to switch and protect the most common motor applications. As shown, the devices are easy to use and are ideal for motor control and protection for motors up to 25 HP.