KB Electronics KBRC-240D User Manual

Page 14

the motor armature voltage. If the tach-generator polarity is reversed, the motor will
accelerate to full speed and the Main Speed Potentiometer will not control speed. Tach-
generator feedback can greatly improve speed regulation and dynamic response.

Note: When using a tach-generator, the IR trimpot should be set fully counterclockwise.

Note: The tach-generator input is designed for 7 Volt or 50 Volt per 1000 RPM tach-gen-
erators used with 1800 RPM motors. For a tach-generator other than 7 Volt or 50 Volt
per 1000 RPM or for motors other than 1800 RPM, an external 1/2 Watt resistor (RT)
must be installed. Install RT in series with the tach-generator, as shown in Figure 16.
Jumper J3 must be set to the “7V” position.

The value of RT in Ω can be calculated using the following formula:
RT = (4.37 X VT X S) - 55000 Where VT is the tach-generator voltage (in Volts per 1000
RPM) and S is the base speed of the motor (in RPM).

Example:
Suppose you have a 20 Volt per 1000 RPM tach-generator with a 3600 RPM motor.
RT = (4.37 X 20 X 3600) - 55000 = 259640

Choose the closest 1/2 Watt resistor value, which is 240000 (240k) or 270000 (270k).
Readjustment of the MAX trimpot may be necessary to achieve the desired maximum
output voltage.

III.

SETTING SELECTABLE JUMPERS
The KBRC-240D has selectable jumpers which must be set before the control can be used.
See Figure 1, on page 7, for location of jumpers.

A. AC Line Input

Voltage
Selection (J1
and J2) –
Jumpers J1
and J2 are
both factory
set to the
“230V”
position for
208/230 Volt AC line input. For 115 Volt
AC line input, set both Jumpers J1 and
J2 to the “115V” position. See Figure 17.

B. Motor Voltage Selection (J3) – Jumper

J3 is factory set to the “A180” position for
180 Volt motors. For 90 Volt motors, set
Jumper J3 to the “A90” position. See
Figure 18.

RELAY

T-

T+

TB3

DC TACH-GENERATOR

FIGURE 15 – DC TACH-GENERATOR

CONNECTION

T+

RELAY

T-

TB3

DC TACH-GENERATOR

FIGURE 16 – DC TACH-GENERATOR

CONNECTION WITH ADDITION OF RT

FIGURE 17 – AC LINE INPUT VOLTAGE SELECTION

FIGURE 18 – MOTOR VOLTAGE

SELECTION

Control Set for 208/230 Volt AC Line Input

(Factory Setting)

Control Set for 115 Volt AC Line Input

J1 Set for 208/230

Volt AC Line

J2 Set for 208/230

Volt AC Line

J1 Set for 115

Volt AC Line

J2 Set for 115

Volt Ac Line

230V 115V

115V 230V

230V 115V

115V 230V

J3 Set for 180 Volt Motor

(Factory Setting)

J3 Set for 90 Volt Motor