Specifications

MODELS 7225AC, 7425AC
LINE-POWERED AC BRUSHLESS SERVO AMPLIFIERS
WITH +/-10V ANALOG U-V INPUTS
ZERO ADJUSTMENT
The current OFFSET potentiometers are factory set to zero
current with zero input. The sum of the three currents U, V and
W can be set to a high degree of resolution by using the
current monitors. After connecting and tuning the motor,
ground the U and V reference inputs, then adjust the offset
potentiometer (see below table) while monitoring the
appropriate current monitor U (J3-10) and V (J3-11) with
respect to Ground (J3-13).
If the U and V currents are correctly set to zero then the W
current will also be zero: Iw = - (Iu + Iv)
POT DEFAULT DESCRIPTION
U OFFSET
(R7 internal)
Center U zero output
current adjustment
V OFFSET
(R6 internal)
Center V zero output
current adjustment
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TRANSCONDUCTANCE ADJUSTMENT
OVERALL GAIN
The current gain or transconductance is the ratio of output
current to input voltage. The transconductance should be set to
provide a better use of the controllers output range, typically a
+/10V DAC. The gain can be set via RH2, RH3, RH7, and
RH8, see below table. All resistor values must be the same.
Use 1% tolerance for good CMRR (common mode rejection
ratio).
It is recommended that the transconductance be set to limit the
peak current delivered to the motor. Most applications require
peak currents of two or three times the motors continuous
current rating. Example: For a typical +/-10V DAC and a
required 15 Amps peak, the transconductance should be set to
15 Amps / 10 Volt = 1.5 Amps / Volt.
The Gain (Amps / Volt) = 2 * Rx
/ (47k Rx he default
gain is 2A/V with RH2, RH3, RH7, and RH8, resistors open or
out of circuit. (Indicated in bold & italic in the table below).
Transconductance Rx = RH2,3,7 &, 8
Gain
Amps/Volt
Rx (
)
2 OPEN
1.5 140k
1 47k
0.5 15.6k
GAIN FINE ADJUSTMENT
The REF GAIN potentiometers are factory set to give a
matched transconductance of 2Amps/Volt, with RH2, RH3,
RH7, and RH8, resistors open or out of circuit. The gain of both
U and V channels can be fine-tuned to match. The range is
about +/-5%. To fine adjust the transconductance, input a
reference voltage, such as 1VDC, to the U Ref (+) (J3-2) and V
Ref (+) (J3-3), Remembering to ground Ref (-) (J3-14, J3-15)
at the source. Then while monitoring the appropriate current
monitor, adjust the REF GAIN potentiometers to match.
POT DEFAULT DESCRIPTION
U REF GAIN
(R1)
Center U Fine gain control
CW increases gain
V REF GAIN
(R2)
Center V Fine gain control
CW increases gain
CURRENT LIMIT
Control of the current limit can be made internally via
component RH18 in the header socket, or externally via
connector pin J3-20. See figure below.
A resistor can be connected between this pin and signal
ground (J3-12, 13, or 16), or the pin can be driven by a voltage
between 0 and +5VDC. Using this technique, the current limit
can be controlled over a range of 100% to 50% of the peak
command current, set by the transconductance.
J3-20
94k
47k
+15V
R
H
18
Rpk
V
ext
0~5VDC
Amplifier
J3-16
Phase
Symmetric
Current
Limiter
CURRENT LIMIT (RH18)
Default values are in bold & italic.
I-limit RH18 Vext
10 31.6k 5
8 16.9k 3.5
6 10.5k 2.5
4 5k 1.4
2 1.3k 0.4
These values are within 10%, typically. For greater accuracy,
measure current monitor and select parts for exact limit value.
Phone: [phone]
Phone: 877-IP-Tech1
Fax: 877-IP-Tech2
www.iptech1.com
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