YASKAWA SGMAH Series 200V AC SERVO MOTOR Industrial Servo Motor SGMAH-A5A1A21

 

Reduced Voltage Starting of Motors
Reduced Voltage Starting connects the motor windings/terminals at lower than normal line voltage during the initial starting period to reduce the inrush current when the motor starts.

• Reduced voltage starting may be required when:
The current in-rush form the motor starting adversely affects the voltage drop on the electrical system.needed to reduce the mechanical “starting shock” on drive-lines and equipment when the motor starts.

• Reducing the voltage reduces the current in-rush to the motor and also reduces the starting torque available when the motor starts.

• All NEMA induction motors can will accept reduced voltage starting however it may not provide enough starting torque in some situations to drive certain specific loads.
If the driven load or the power distribution system cannot accept a full voltage start, some type of reduced voltage or "soft" starting scheme must be used.

• Typical reduced voltage starter types include:
1. Solid State (Electronic) Starters
2. Primary Resistance Starters
3. Autotransformer Starters
4. Part Winding Starters
5. Wye-Delta Starters

Reduced voltage starters can only be used where low starting torque is acceptable or a means exists to remove the load from the motor or application before it is stopped.

 

 

 

Stepper motors can often exhibit a phenomena refered to as resonance at certain step rates. This can be seen as a sudden loss or drop in torque at certain speeds which can result in missed steps or loss of synchronism. It occurs when the input step pulse rate coincides with the natural oscillation frequency of the rotor. Often there is a resonance area around the 100 – 200 pps region and also one in the high step pulse rate region. The resonance phenomena of a stepper motor comes from its basic construction and therefore
it is not possible to eliminate it completely. It is also dependent upon the load conditions. It can be reduced
by driving the motor in half or microstepping modes.

 

 

When one step pulse is applied to a stepper motor the rotor behaves in a manner as defined by the above curve.
The step time t is the time it takes the motor shaft to rotate one step angle once the first step pulse is applied.
This step time is highly dependent on the ratio of torque to inertia (load) as well as the type of driver used.
Since the torque is a function of the displacement it follows that the acceleration will also be. Therefore, when moving in large step increments a high torque is developed and consequently a high acceleration. This can cause overshots and ringing as shown. The settling time T is the time it takes these oscillations or ringing to cease. In certain applications this phenomena can be undesirable. It is possible to reduce or eliminate this behaviour by microstepping the stepper motor. For more information on microstepping please consult the microstepping note.