Yaskawa Electric SERVOPACK 4.0KWatt Industrial Servo Drives SGDB-50ADD

Current Source Input (CSI)
The CSI is very similar to the VVI except that it is more sensitive to current as opposed to a VVI
drive which is more sensitive to voltage.
C CSI drives are usually lower cost above 50 horsepower than VVI drives for pumps and fan
applications.
C The efficiency of a CSI drive may not be as high as a VVI drive and may not provide a total
energy saving package compared to other drives.
C Due to the current characteristics produced by the CSI, cogging can be a problem at low
speeds similar to the VVI.
C The voltage output is somewhat closer to the regular sine wave expected by the motor except
for the sharp spikes and
sags.
Advantages:
High Efficiency
Optional Regeneration
Capability
Inherent Short Circuit Protection
Capable of bringing other motors
on Line at full voltage
Disadvantages:
Power Factor decreases with
decreasing speed.
Low Speed Motor Cogging (shaft
pulsing/jerky motion)
Inability to operate more than one motor on the drive at a time
Poor ride through ability for low input voltage
Generally sold as Motor/Drive package.
Motor requires a feedback device (tachometer, etc.) to work with the drive
Cannot test drive without motor connected
Requires Isolation Transformer on Input Side
Large physical size of Drive due to internal power components

So far we have assumed that the source of the magnetic Weld is a permanent magnet. This is a convenient starting point as all of us are familiar with magnets, even if only of the fridge-door variety. But in the
majority of motors, the working magnetic Weld is produced by coils of wire carrying current, so it is appropriate that we spend some time looking at how we arrange the coils and their associated iron ‘magnetic circuit’ so as to produce high magnetic Welds which then interact with
other current-carrying conductors to produce force, and hence rotation.
Electric Motors 7
First, we look at the simplest possible case of the magnetic Weld surrounding an isolated long straight wire carrying a steady current
(Figure 1.4). (In the Wgure, the þ sign indicates that current is Xowing into the paper, while a dot is used to signify current out of the paper: these symbols can perhaps be remembered by picturing an arrow or dart, with the cross being the rear view of the Xetch, and the dot being the approaching point.) The Xux lines form circles concentric with the wire, the Weld strength being greatest close to the wire. As might be expected, the Weld strength at any point is directly proportional to the current. The convention for determining the direction of the Weld is that the positive direction is taken to be the direction that a right-handed corkscrew must be rotated to move in the direction of the current.
Figure 1.4 is somewhat artiWcial as current can only Xow in a complete circuit, so there must always be a return path. If we imagine a parallel ‘go’ and ‘return’ circuit, for example, the Weld can be obtained by
superimposing the Weld produced by the positive current in the go side with the Weld produced by the negative current in the return side, as shown in Figure 1.5.
We note how the Weld is increased in the region between the conductors, and reduced in the regions outside. Although Figure 1.5 strictly only applies to an inWnitely long pair of straight conductors, it will probably not come as a surprise to learn that the Weld produced by a single turn of wire of rectangular, square or round form is very much the same as that shown in Figure 1.5. This enables us to build up a picture of the Weld
Figure 1.4 Magnetic Xux lines produced by a straight, current-carrying wire
Figure 1.5 Magnetic Xux lines produced by current in a parallel go and return circuit
8 Electric Motors and Drives
that would be produced in air, by the sort of coils used in motors, which typically have many turns, as shown for example in Figure 1.6.

OTHER SUPERIOR PRODUCTS