32
SSA - Rev 6/98
The velocity loop is closed by connecting the following terminals:
Terminal M1 to terminal 4.
Terminal M2 to terminal 3.
The reference signal is fed to input 1 and R1 should be calculated as follows:
Vs
K = -----
Vam
Vam - armature voltage at maximum application speed
R1 = 20xV1mxK - 100 (Kohm)
V1m - maximum reference voltage at input 1.
Reducing the DC and AC gains of the error amplifier by increasing C3 and R11 is
recommended. The final values depend on the type of motor and mechanical load, so
optimum results will be achieved by the empirical method. Using this method a
speed range of 20:1 and ±3% speed accuracy may be achieved.
Calculating R61 for IxR compensation
In order to improve the speed stability in various load conditions, an IxR
compensation is required. This is achieved by inserting R61. The value of R61 can
either be achieved empirically (chapter 8.4) or by using the following equation:
2.4xVam(R1+100)
R61 = ----------------- (Kohm)
IcxV1mxRa
R1, Vam, V1m same values as above.
Ic - Amplifier's nominal current
Ra - Total armature resistance in Kohm
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