Although servo systems can very precisely control motor speed, position, and torque, in some applications, the motor may not be able to reach the commanded velocity due to limits in the available bus (supply) voltage from the drive. But advanced servo drives offer a technique referred to as field weakening, which alters the motor’s torque-speed […]
AC Motors
What does motor insulation class specify and why is it important?
Any time current flows through a wire — such as the windings in a motor — resistance in the wire, as well as other losses, cause heat to be generated. This heat will eventually transfer to other parts of the motor, causing them to degrade over time. One of the key components affected by this […]
What is inrush current in an AC motor and why does it matter?
When an electrical device, such as an AC induction motor, is switched on, it experiences a very high, momentary surge of current, referred to as inrush current. When an AC induction motor is started, the supplied voltage creates a magnetic field in the stator, which induces a magnetic field in the rotor. The interaction of […]
What is a motor control center (MCC)?
Manufacturing plants often contain dozen, if not hundreds, of motors — driving everything from packaging and processing equipment to fans and pumps. Motor control centers allow facilities such as these to centralize control of some or all of their motors into one location. The basic structure of a motor control center (MCC) is a metal cabinet […]
What are thermal overload relays and what motion components do they protect?
Heat is a major factor in the performance and life of a motor, and one of the primary sources of motor heating is current running through the motor windings. Since heating is an unavoidable condition of motor operation, it’s important to protect the motor from overheating, or thermal overload. In a previous post, we described […]
What’s the difference between dynamic braking and regenerative braking?
When a motor’s rotor speed is greater than its synchronous, or designated, speed, it can act as a generator, creating electrical energy from mechanical energy. This electrical energy needs somewhere to go, and there are two ways to deal with it — dissipate it as heat, or reuse it. Dynamic braking takes the energy generated […]
What are bearing currents and what causes them?
Pulse-width modulation is a fundamental operating principle of variable frequency drives (VFDs), but the high-frequency switching that delivers pulses of voltage from the drive to the motor can cause bearing currents — high-frequency currents that flow through the motor bearings, often leading to damage and premature failure. To achieve pulse-width modulation, insulated gate bipolar transistors (IGBTs) […]
What is cable ringing between AC drives and motors and how can it be avoided?
Variable frequency drives use a technique referred to as pulse-width modulation (PWM) to provide voltage of varying frequency to an AC induction motor. The inverter, or output, stage of the VFD uses insulated gate bipolar transistors (IGBTs) that switch on-and-off rapidly, creating trapezoidal pulses of varying width to simulate AC sinusoidal voltage. But the windings in […]
What are drive isolation transformers and how do they differ from line reactors?
A variable frequency drive alters the speed of an AC induction motor by rectifying incoming AC power to DC, storing the DC power in a bus, and then converting the DC power back to AC at the voltage and frequency required to meet the load demands. Although this matching of the motor speed to the […]
Nippon Pulse introduces new high-resolution, high-torque miniature AC servomotors
Nippon Pulse America, Inc. is pleased to introduce its new series of high-performance micro direct-drive (MDD) AC servomotors. The new MDD motors will join Nippon Pulse’s existing line of Linear Shaft Motor servomotors. Each compact MDD motor comes with a built-in high-performance encoder (either absolute or incremental) that enables direct fine positioning. The motors are […]
