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Starter Overload Relays

The starting overload relay is an essential part of a motor control system and provides protection against excessive currents of both immediate and long duration. It operates in conjunction with the motor starter and contactor to ensure the safe and reliable operation of motors, running at all sorts of loads even under less-than-ideal conditions.

The types of overload relays found today include IEC overload relays and electronic overload relays. The former are used in order to protect against overcurrent conditions, while the latter can sense more types of anomalies, including phase loss. Either way, these relays provide an added level of safety for motors and other equipment operating in a circuit together with them.

Typically installed in series with the motor circuit, and often mounted directly on the motor starter or control panel, is the overload relay. It watches the current flowing through the motor and turns on a protection action when that current increases above a set threshold. This can shut off whatever circuit supplies power to the motor (closing an electromagnetic switch or opening contactors) or send a signal telling whatever monitoring device there is that it should make the motor stop operating safely.

Found 393 items
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Found 393 items
Manufacturer
ABB (67)
Benshaw (101)
Lovato (20)
Schneider Electric (205)
Component
Bimetallic Overload Relay (101)
Electronic Thermal Overload Relay (4)
IEC Overload Relay (184)
NEMA Overload Relay (12)
Overload Relay (67)
Overload Relay Thermal Unit (9)
Thermal Overload Relay (16)
Sub Component
Motor Logic Solid State Overload Relay (12)
NEMA Style Melting Alloy Overload Relay (9)
Tesys K Non-Differential Thermal Overload Relay (15)
Tesys LRD Electronic Overload Relay (135)
Tesys LRF Electronic Overload Relay (14)
Tesys T Smart Overload Relay (20)
Starter Voltage
100-240 VAC (13)
690 VAC (101)
Starter Coil Voltage
600 VAC (6)
Starter Amperage
0.16 Amp (2)
0.23 Amp (1)
0.25 Amp (2)
0.36 Amp (1)
0.4 Amp (2)
0.54 Amp (1)
0.63 Amp (4)
0.8 Amp (1)
0-2 Amp (2)
1 Amp (4)
Starter Model
LR2D (7)
LR2K (14)
LR3D (50)
LR7K (1)
LR9D (9)
LRD (69)
Starter Class
Class 10 (14)
Class 10A (17)
Class 5-30 (3)
Starter Current Rating
0.1–0.16 Amp (1)
0.16–0.25 Amp (1)
0.25–0.4 Amp (1)
0.4–0.63 Amp (1)
0.63–1 Amp (1)
1.6–2.5 Amp (2)
100–160 Amp (4)
1–1.6 Amp (2)
110–150 Amp (2)
120–180 Amp (2)
Starter Housing
IP20 (101)
Starter NEMA Size
0 (4)
00 (1)
1 (3)
2 (5)
3 (4)
4 (4)
5 (2)
Starter Poles
Two Pole (16)
Starter Height
3.31" (2)
4" (1)
4.06" (1)
5.59" (1)
6.97" (1)
Starter Width
3.5" (2)
3.53" (1)
4.28" (1)
5.31" (2)
Starter Length
3.97" (3)
4" (1)
5.75" (2)
Normally In Stock
Lovato RFS383800 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$208.99
$174.16
Normally In Stock
Lovato RFS383200 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$208.99
$174.16
Normally In Stock
Lovato RFS382500 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$130.31
$108.59
Normally In Stock
Lovato RFS382300 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$130.31
$108.59
Normally In Stock
Lovato RFS381800 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$130.31
$108.59
Normally In Stock
Lovato RFS381400 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS381000 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380650 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380400 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380250 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380160 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380100 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380063 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380040 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380025 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFS380016 Thermal Overload Relay - Single Phase, Two Pole
Free U.S Ground shipping
$112.48
$93.73
Normally In Stock
Lovato RFE454500 - Electronic Thermal Overload Relay, 32 Amp
Free U.S Ground shipping
$249.31
$207.76
Normally In Stock
Lovato RFE453200 - Electronic Thermal Overload Relay, 32 Amp
Free U.S Ground shipping
$249.31
$207.76
Normally In Stock
Lovato RFE450800 - Electronic Thermal Overload Relay, 8 Amp
Free U.S Ground shipping
$249.31
$207.76
Normally In Stock
Lovato RFE450200 - Electronic Thermal Overload Relay, 2 Amp
Free U.S Ground shipping
$249.31
$207.76
Normally In Stock
Benshaw SPO-800H-660A Bimetallic Overload Relay - 690 V, 520–800 Amp, Class 20
Free U.S Ground shipping
$990.66
$825.55
Normally In Stock
Benshaw SPO-800H-500A Bimetallic Overload Relay - 690 V, 400–600 Amp, Class 20
Free U.S Ground shipping
$990.66
$825.55
Normally In Stock
Benshaw SPO-800H-350A Bimetallic Overload Relay - 690 V, 260–400 Amp, Class 20
Free U.S Ground shipping
$990.66
$825.55
Normally In Stock
Benshaw SPO-800H-250A Bimetallic Overload Relay - 690 V, 200–300 Amp, Class 20
Free U.S Ground shipping
$990.66
$825.55
Normally In Stock
Benshaw SPO-400H-350A Bimetallic Overload Relay - 690 V, 260–400 Amp, Class 20
Free U.S Ground shipping
$332.04
$276.70
Normally In Stock
Benshaw SPO-400H-250A Bimetallic Overload Relay - 690 V, 200–300 Amp, Class 20
Free U.S Ground shipping
$332.04
$276.70
Normally In Stock
Benshaw SPO-400H-200A Bimetallic Overload Relay - 690 V, 160–240 Amp, Class 20
Free U.S Ground shipping
$332.04
$276.70
Normally In Stock
Benshaw SPO-400H-130A Bimetallic Overload Relay - 690 V, 100–160 Amp, Class 20
Free U.S Ground shipping
$332.04
$276.70
Normally In Stock
Benshaw SPO-220H-200A Bimetallic Overload Relay - 690 V, 160–240 Amp, Class 20
Free U.S Ground shipping
$283.04
$235.87
Normally In Stock
Benshaw SPO-220H-130A Bimetallic Overload Relay - 690 V, 100–160 Amp, Class 20
Free U.S Ground shipping
$283.04
$235.87
Normally In Stock
Benshaw SPO-220H-80A Bimetallic Overload Relay - 690 V, 65–100 Amp, Class 20
Free U.S Ground shipping
$283.04
$235.87
Normally In Stock
Benshaw RMSO-150H-130A Bimetallic Overload Relay - 690 V, 110–150 Amp, Class 20
Free U.S Ground shipping
$183.25
$152.71
Normally In Stock
Benshaw RMSO-150H-113A Bimetallic Overload Relay - 690 V, 95–130 Amp, Class 20
Free U.S Ground shipping
$183.25
$152.71
Normally In Stock
Benshaw RMSO-150H-93A Bimetallic Overload Relay - 690 V, 80–105 Amp, Class 20
Free U.S Ground shipping
$183.25
$152.71
Normally In Stock
Benshaw RMSO-150H-65A Bimetallic Overload Relay - 690 V, 54–75 Amp, Class 20
Free U.S Ground shipping
$183.25
$152.71
Normally In Stock
Benshaw RMSO-150H-42A Bimetallic Overload Relay - 690 V, 34–50 Amp, Class 20
Free U.S Ground shipping
$183.25
$152.71
Normally In Stock
Benshaw RMSO-95H-90A Bimetallic Overload Relay - 690 V, 80–100 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-80A Bimetallic Overload Relay - 690 V, 70–95 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-74A Bimetallic Overload Relay - 690 V, 63–85 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-65A Bimetallic Overload Relay - 690 V, 54–75 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-55A Bimetallic Overload Relay - 690 V, 45–65 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-42A Bimetallic Overload Relay - 690 V, 34–50 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-34A Bimetallic Overload Relay - 690 V, 28–40 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-30A Bimetallic Overload Relay - 690 V, 24–36 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-95H-21.5A Bimetallic Overload Relay - 690 V, 18–25 Amp, Class 20
Free U.S Ground shipping
$137.89
$114.91
Normally In Stock
Benshaw RMSO-63H-55A Bimetallic Overload Relay - 690 V, 45–65 Amp, Class 20
Free U.S Ground shipping
$112.49
$93.74
Normally In Stock
Benshaw RMSO-63H-42A Bimetallic Overload Relay - 690 V, 34–50 Amp, Class 20
Free U.S Ground shipping
$112.49
$93.74
Normally In Stock
Benshaw RMSO-63H-34A Bimetallic Overload Relay - 690 V, 28–40 Amp, Class 20
Free U.S Ground shipping
$112.49
$93.74

FAQs

What communications capabilities do three phase motor overloads have to provide overload protection and phase loss protection to motors?

Three-phase motor overloads often have communications capabilities such as Modbus, Profibus, or Ethernet/IP, allowing them to provide real-time data on motor performance, fault conditions, and protection status to centralized control and monitoring systems.

What role does a heater element and a ratchet wheel play in an overload relay's ability to provide protection to motors?

In an overload relay, the heater elements generates heat proportional to the motor's current, causing the ratchet wheel to move and eventually trip the relay if the current exceeds safe levels, thus protecting the motor from overheating.

Motor Control Basics

Motor control allows operational control of electrical motors in various environments. 

Motor control circuits provide a safe way to operate electrical motors. Back when motor control circuits were in their infancy, it would have been common to see a simple disconnect switch that would be used to turn on and off a motor. Depending on the size of the motor and how much voltage was required, operating this disconnect would have been dangerous, with a very high possibility of arcing or electrocution. Not to mention that when the disconnect was actuated, the large amount of inrush current would have damaged the motor over time.

In today's motor control circuits, there are a few common pieces of hardware. 

A circuit breaker is used to protect the motor and any hardware downstream. A contactor and an overload relay are connected together and function in tandem to allow for remote and safe operation of the motor. The contactor functions much like a relay, allowing for a smaller electrical circuit to remotely close the motor contacts, starting the motor. The overload relay is designed to protect the motor in the case of a prolonged overcurrent event. These two devices are wired in series, so that if the overload relay detects an overcurrent event, the contactor will open the motor contacts, shutting off power to the motor.

The other two most common types of motor control hardware are a soft starter and a Variable Frequency Drive (VFD). 

Both of these devices function in a similar way to the motor circuit with some added functions. The soft starter is designed to reduce large inrush current to the motor upon startup. This “soft starting” of the motor will prolong its life and allow for safer operation. The VFD performs the soft start functions, but also allows for speed control of the motor. This speed control is critical in many different environments and has made VFDs one of the most common and safe to use motor control circuits today.