Attached to every sanitary pump is a motor of some kind. As we bring you more information about sanitary pumping applications, we wanted to use this post to share some of the information found on a motor name plate.
Most sanitary pumps are powered by what is called a 3 phase squirrel cage motor. These motors have two high level classifications- NEMA for the USA and IEC for European and Asian motors. For this post, we will focus on the North American Electrical Manufacturers Association (NEMA) and their standard for motor nameplates.
So what does NEMA say has to be on the nameplate? Here is what must be on every NEMA nameplate:
- Manufacturer Type
- Time Rating
- Service Factor
- Frame Size
- Design Code
- Rated Horsepower
- Rated Voltage & Amps
- Rated Full-load Amps for each voltage level
- Rated Full-load speed
- Insulation Class
- Rated Ambient Temperature
- Locked-rotor code letter
Let us continue by taking a closer look at some of these categories:
Manufacturer’s Type- while NEMA requires this, there is no industry standard motor “type”. Typically, motors are referred to as either single or 3 phase. They may also be classified by their purpose- general or special. Type usually isn’t that helpful in specifying a replacement motor unless you also note the specific motor manufacturer.
Service Factor- or SF is required on a nameplate only if it is higher than 1.0. Industry standards are typically 1.15 for an “open” motor and 1.0 for a totally enclosed (TEFC) motor. Higher service factors, however, do exist
Efficiency- Efficiency is defined as output power divided by input power expressed as a percentage. Manufacturers guarantee the efficiency of a motor within a tolerance band.
Frame Size- this is one of the most important fields in specifying a replacement motor or even pump. We always need to know the frame size. The frame size sets important mounting dimensions such as foot hold mounting pattern and bolt hole dimensions. The first two digits of the frame size divided by 4 gives us the height of the shaft centerline from the bottom of the feet. So the 140TC motor frame would have 3.5” shaft height from the bottom of the feet. The third digit in the frame size determines the distance between the foot holes nearest the shaft and the opposite drive-end foot holes. We’ll spend more time focusing on frame size in an upcoming post.
Horsepower- Shaft horsepower is a measure of the motor’s mechanical output- the ability of a motor to deliver the torque required for the load at a rated speed. More commonly, we know this as “HP” on a nameplate.
Rated Voltage & Amps- voltage is extremely important for properly wiring and using a motor. Motors are commonly nameplated for a wide variety of voltages. For example, 230 and 460V (230/460V). Voltage tolerances are typically +/- 10%, so this motor would be operable at 208V, but we would have to “de-rate” other parameters of the motor, including power factor, efficiency, torque, and current. These are all provided at a rated voltage and frequency.
Rated Full-load Amps- this one is relatively straight forward. Rated full load amps is the amount of current the motor is designed to draw at the rated horsepower.
Rated Full-load Speed- this is the speed at which rated full-load torque is delivered at the rated power output. This is generally given in the units of revolutions per minute or RPM. This is not the same as motors synchronous speed. There will always be some slip. For example, an 1800 RPM synchronous speed might have a full load speed of 1750 RPM.
Frequency- this is almost always 50 or 60 Hz. When more than one frequency is nameplated, other parameter that will differ at different input frequencies must be defined on the nameplate. This is also important in applications using variable frequency drives, which will be the subject of a future post.
Phase- this one is straightforward, representing the number of AC power lines supplying the motor. We typically supply single or three phase motors.
Insulation Class- this is the industry standard classification of the thermal tolerance of the motor winding. Insulation class is a letter designation such as “A”, “B”, or “F”, given the winding’s ability to survive a given operation temperature for a given period of time. The later in the alphabet the letter, the better the life. For example, a motor with class F insulation has a longer life at a given temperature than a motor with class A insulation.
Enclosure Type- this classifies the motor as to its degree of protection from its environment and its method of cooling. Most motors we see are TEFC or totally enclosed fan cooled. Additional designations, such as wash down duty (for high pressure, direct spray applications) and explosion proof motors are also called out here. We’ll talk more about enclosures in future posts.
Hopefully, this gives you a good overview of all the information jammed onto your motor nameplate. If you need help with any of the motors driving your sanitary pumps, contact a Triplex Sales Engineer today!