KB Electronics KBRG-255 - Manual (Page 10)

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For example, if the tach is 25V/KRPM and the motor speed is 3,600 RPM, use the "50V"
J4 position. For other tach-generator voltages and motor speeds, an external resistor
(RT) may be used as follows.
i. Install resistor in series with either tach-generator lead.
ii. Place J4 in "7V" position.
iii. The value of RT is calculated as follows.
RT = [(5.4 x Vt x S) - 68,000] VT = Tach voltage in volts/1000 RPM
Choose the closest standard 1/2 watt S = Base Speed of motor in RPM
resistor value to the calculated value
B. J5 - Feedback Type – The KBRG-255 can be operated in either armature feedback
"AFB" or tach-generator feedback "TFB." Armature feedback provides adequate load
regulation for most applications. For very precise performance, tach-generator feedback
"TFB" should be used. (Note: If tach feedback is desired, an external DC tach-generator
must be used and connected as per instructions.) (See section V J, p. 10 for tach-
generator wiring.) (Note: The IR Comp trimpot must be set to the minimum setting [CCW]
for tach feedback.)
C. J6 - Current Limit (CL) Mode – The KBRG-255 contains electronic current limiting that
limits the maximum DC current to the motor. Two modes of current limit are provided:
1. Timed Current Limit "TCL" – Turns the drive off after a preset time. (The time period
is adjustable with the TCL trimpot from 1-15 seconds and is factory set for
approximately 5 seconds.) In order for the Timed CL feature to operate, the
Start/Stop circuit must be wired. To restart drive after it has "timed out," the Start
button must be pressed.
Application Note: The “TCL” feature cannot be used in either torque mode, since
nuisance tripping will occur.
2. Non-Timed Current Limit "NTCL" – In this mode, the drive will reach preset Current
Limit during overload and stay at that level until drive is turned "off" or fuse blows. If
Non-Timed CL is desired, move jumper J6 from the factory set "TCL" position to the
"NTCL" position.
IV. MOUNTING.
Mount the KBRG-255 in a vertical position (connection terminals in down or up position) on
a flat surface free of moisture, metal chips, or corrosive atmosphere. (Note: If drive is
mounted in other than a vertical position, decrease maximum allowable ambient temperature
by 10 ºC.) (See Mechanical Specification fig. 5, p. 8.) A 5K ohm Remote Speed potentiometer
is provided with each control. Install potentiometer using hardware provided. Be sure to
install insulating disk between potentiometer and inside of front panel.
Enclosure – When mounting the KBRG-255 in an enclosure, it must be large enough to allow
for proper heat dissipation. A 18"x24"x36" enclosure is suitable for the KBRG-255 at full
rating. Smaller enclosures may be used if full rating is not required.
V. WIRING. Warning! Read Safety Warning before attempting to use this control.
Warning! To avoid erratic operation do not bundle AC Line and motor wires with
potentiometer, voltage following, enable, inhibit or other signal wiring. Use shielded
cables on all signal wiring over 12" (30 cm) – Do not ground shield.
Wire control in accordance with National Electric Code requirements and other local codes
that apply. Be sure to fuse each conductor which is not at ground potential (do not fuse
neutral or grounded conductors). (See section VI, p. 10, for fuse information.) Wire control
in accordance with connection diagrams (see figs. 3,4,6 & 7A-E). A separate AC line switch
or contactor must be wired as a disconnect switch to control so that contacts open each
ungrounded conductor. See table 4 p. 7 for terminal block wiring information.