Category: Motors

Working With Motors

Motors are fine devices when they're properly hooked up. They can also be frustrating parts when they shut down at inopportune times and need repair. Setting up the motor in the proper manner is a simple way of reducing any downtime. Get to know the fine details surrounding motor setup so that your industry purrs with efficiency every day.

1. Thermal Overload Setup

A common mistake during motor-protection setup is miscalculating the thermal overload setup. In general, motors can take on 125 percent of their full-load current setting. This function may or may not be built into the motor already.

If the motor has the 125-percent setting, match the relay to the nameplate's printed current. Alternatively, you must add 25 percent to the printed current in order to set up the overload without any faults.

2. Improper Undervoltage Protections

You don't want to apply too much voltage to a motor, and applying too little is also a concern. Motors can fail with a drop in voltage. Be sure to set the undervoltage protection at 90 percent below the rated voltage. Deviating from this value can cause motor shutdowns and inefficient production. If a motor continues to act erratically, an undervoltage issue is usually the culprit.

3. Miscalculated Magnetic Protection Setup

Test the magnetic protection before allowing a motor to operate with the system. Make sure that the incoming current is allowed to flow even when the magnetic protection shuts down the motor. This design gives the motor a chance to power down without too much strain on the internal parts. Magnetic protections can be either fixed or adjustable, so pay careful attention to your system. The setup will be different for both of these protections.

4. Motor Nameplate Specifics

There's a surprising amount of information that's required by NEMA or the National Electric Manufacturers Association on each motor. Each item tells a story about the motor's strength and applications.

  • Manufacturer's Type. Is the motor a single- or three-phase design? The type tells you this information. There might be a motor purpose described here as well.
  • Rated Voltage. One of the most important details on any motor is the rated voltage. The motor should have peak efficiency at this voltage.
  • Full-Load Current. No motor should be used at a current that's higher than the value printed on the motor nameplate.
  • Rated Frequency. The frequency in which the motor runs is also a reflection of its location. The United States typically has motors with a 60Hz rating, for example.
  • Phase Value. Choose between either single- or three-phase designs on your motor.
  • Full-Load RPM Rating. How fast does the motor rotate when fully loaded? This RPM rating is critical to safe operations.
  • Insulation Class. This rating simply reflects the maximum temperature that a motor can withstand during operations. It includes the internal and external temperatures as references.
  • Time Rating. Carefully follow the time rating on the motor because it can't operate past this value. Luckily, many of today's high-quality motors are rated for continuous use.
  • Horsepower. The motor's shaft offers a certain amount of horsepower, which is the value reflected on the NEMA nameplate.
  • Locked Rotor Code. A letter denotes the normal, startup current entering the motor. This rating is important because it gives technicians a guideline during installation.
  • Power and Service Factors. These values define the real energy moving into the motor and how much it can handle when overloaded, respectively.
  • Efficiency. This value is a comparison of the mechanical versus electrical outputs that a motor can provide.
  • Frame Size. Frame size is basically a dimensional view of the motor.
  • Design Letter. Torque and current designations are described through letters assigned by NEMA.

Get in touch with Kurz today for all of your motor needs. Our industry solutions can make a difference in your productivity. A reliable motor can keep you going for years to come.