There are a few different types of motor starters. This section of information will cover the most common type, which includes an electrical contactor and an overload.
When you purchase a motor starter you are buying two devices. The contactor serves as an electrically activated switch and the overload serves as a motor protector.
The contactor is usually known by its horsepower ratings at different Voltages and by what Voltage is used to "activate" it.
An overload is known by its Amp trip ratings along with how long it takes to trip when exceeding its trip rating.
Additionally the two devices will have "size" ratings or frame sizes. Since the two devices connect together to make a motor starter- the device sizes must be compatible.
In North America, until recently, most all motor starters were sized by Nema frame sizes. This CHART explains the sizes in the Nema frames. Now, International frame sizes dominate the world market. These are known as IEC sizes. There are many many more IEC frame sizes than Nema frame sizes which means an exact motor starter can be used without unnecessary oversizing. An example would be a Nema size 2 motor starter vs a Nema size 3 motor starter. In IEC sizes there are three sizes between Nema size 2 and size 3 which not only saves cost but also space. More information about Nema vs IEC motor starters can be found HERE. And a comparison chart HERE.
Elimia motor starters are manufactured by LSis in Korea. LSis parent company is LG in Korea. LSis in North America is know as LS America and based in Illinois.
LS America motor starters are both Nema rated and IEC rated where the sizes overlap. Example is Nema size 2 vs IEC size 40, these are the same rating and verified by the UL rating on the label on the contactor.
All the contactors and overloads we use and sell are UL listed or certified and UL HP rated and all are rated at least 600VAC.
The Contactor:
Basically a contactor is a switch. But, unlike a switch, a contactor is activated by a Voltage applied to a coil of wire. The Voltage applied to the coil creates a magnetic field which makes the contactor activate. As long as the correct Voltage remains on the coil - the contactor will remain activated.
The Voltage applied to the coil of the contactor is or can be independent and different from the Voltage passing through the contacts of the contactor. In other words, a contactor may use 120VAC to activate it but have 480VAC going through the contacts. This is very common.
To activate a contactor requires just a tiny amount of power. This allows low current devices known as pilot devices to be used to activate the contactor. So, an on/off switch rated at 1 Amp can be used to activate a contactor passing 100 Amps or more.
The ratings of our contactors are found in the product listings specific to that device and the complete technical specifications can be found HERE.
The Overload:
Overloads are not rated by horse power but by current (Amps).
The type of overload we use and sell will have an Amp range that can be set by a dial on the overload. This is known as the trip setting.
The trip setting is determined by the motor Full Load Amps, sometimes labeled FLA or Amps or just "A" on the motor label, along with Voltage used to power the motor.
Sometimes, a motor will also be labeled with Service Factor Amps. Or it could be labeled just SF for the service factor. SF values will likely be 1.00, 1.15 or 1.25.
The trip setting should never be set higher than the SFA or a multiplication of FLA times SF. If a motor is rated at 15 Amps with a SF of 1.15 the maximum trip setting should be no more than 17.25 Amps. Additionally, if your motor FLA is rated at 230V and your actual Voltage is 240V, this should be considered. Remember, high voltage means lower Amps.
Another important factor to consider with overloads is the trip time. If your motor is very hard to start or takes a long time to come up to full speed, you may need a special overload. The trip time of overloads is known as trip Class. Class 10 is the most common and should be used in almost every application. Class 20 overloads are used for long starting and hard start loads. But, keep in mind, increasing the trip time diminishes the motor protection provided by the overload, which is the job of the overload.
Our overloads are equipped with both manual and automatic trip reset capabilities. When an overload trips it cannot be immediately reset. A bimetal strip inside the overload heats up during normal operation. When the Current going through the overload exceeds the set point for an a certain amount of time, the overload trips. This is done by activating a relay type contact. This contact is wired in a manner to the contactor coil to de-activate the contactor and shut down the motor. It takes 5 minutes or longer for the overload to cool down enough to be reset. If the overload is set for automatic reset this is done automatically when it cools down.
All the overloads we provide as standard have a differential type overload feature. Differential thermal overloads monitor each phase. In other words, if one phase is not passing the same amount of Current - the overload knows it and trips due to phase imbalance. This is an important feature in protecting motors due to phase loss or single phasing out. This feature also affects the way we wire a motor starter for single phase applications. For single phase applications, all three main power connections on the starter must be used. So, for 230V single phase, one phase must run through the starter two times and for 120V single phase the single hot phase is run through the starter three times. Examples of this technique can be viewed HERE.
Overloads are specific in mating size. Example- IEC size 12 overload mates to Contactor size 9, 12 and 18. This is something that must be reviewed when purchasing individual parts or replacement parts.