8.6
Many motors are used in sensitive applications that require that specific limits of radiated or conducted electromagnetic interference not be exceeded.
Electromagnetic interference (EMI), sometimes referred to as radio-frequency interference (RFI), is a phenomenon which can directly or indirectly contribute to a degradation in performance of electronic receivers or systems. EMI consists of undesirable voltages and currents that reach the affected device either by conduction through the power lines or by radiation through the air and cause the device to exhibit undesirable performance.
AC induction motors do not generally have any EMI problems unless they are powered by some type of electronic drive.
Mechanically commutated motors and electronically controlled motors may emit significant amounts of EMI. The emissions are regulated by various governmental agencies throughout the world. The International Electrotechnical Commission (IEC) has three technical committees (TCs) that work on EMI standards. They are the International Committee on Radio Interference (CISPR);TC77, which is concerned with electromagnetic compatibility (EMC) of electrical equipment; and TC65, which is concerned with immunity standards. The CISPR 10 and CISPR 23 standards are results of the committee’s work.
In the United States, the Federal Communications Commission (FCC) regulates EMI. In Europe, the European Commission (EC), through the European Standards
TABLE 8.11 Summary of DC Motors
| Motor Type | Eff, % | Characteristics | Typical applications |
| Iron-core PMDC | 40-90 | Straight-line S-T curve, good controllability, battery operation, good thermal properties | Servo systems, printers, actuators, pumps, automotive, medical equipment, vending, robotics |
| Moving-coil hollow-rotor PMDC |
40-85 | Straight-line S-T curve, good controllability, battery operation, poor thermal properties, high acceleration rate, low inertia | High-speed printers, high-speed servo systems, robotics |
| Brushless PMDC | 30-90 | Straight-line S-T curve, good controllability, requires a controller and Hall effect switches or back-emf sensors, battery operation, good thermal properties, long life | Servo systems, robotics, medical equipment, disk drives, pumps |
| Stepping motor | N/A | Moves in increments of 15 to 0.9°, open-loop controllability (no position sensors necessary) | Printers, actuators, disk drives, robotics, automotive |
| Switched reluctance | 30-90 | High acceleration rate, high speed, no back-emf generated, requires a feedback device and controller | Servo systems, pumps, vacuum cleaners, printers |
| Series-connected wound field | 40-60 | High starting torque, high no-load speed, steep S-T curve, poor speed regulation, can be made to operate on ac or dc | Power tools, fans, vacuum cleaners, appliances, sewing machines, saws |
| Shunt-connected wound field | 50-70 | Good speed regulation, flat S-T curve, controllability | Conveyors, saws, large power tools, pumps |
| Compound-connected wound field | 60-80 | Very high starting torque, flat S-T curve in operating range, good controllability | Large power tools, pumps, conveyors, traction drives |
TABLE 8.12 Summary of AC Motors
| Motor type | Eff, % | Characteristics | Typical applications | |
| Split phase | 50-70 | Moderate starting torque,high starting current | Pumps, blowers, tools, fans, appliances, furnaces | |
| 0 J | Capacitor start | 60-75 | High starting torque, low starting current | Pumps, blowers, fans, tools, appliances, air conditioning |
| Permanent split capacitor | 35-70 | Low starting torque, low starting current, multispeed | Fans, furnaces, air conditioning, blowers, actuators, garage door openers | |
| Shaded pole | 20-35 | Low torque, low starting current, multispeed, low efficiency | Fans, blowers, appliances, actuators, vending machin | |
| Three phase | 70-90 | High efficiency, very high starting torque, low starting current, requires three-phase power supply | Machinery, industrial pumps and equipment, large compressors |
Committee (CEN) and the European Committee for Electrotechnical Standards, has adopted harmonized EMC standards. They cover Class 1 (residential, commercial and light industry) and Class 2 (heavy industry) standards for testing. Some standards of concern here are listed in Table 8.13.
