KB Electronics KBMG-212D User Manual

Page 30

FIG. 19 – DEAD BAND TRIMPOT ADJUSTMENT

Note: A 4-quadrant

ACCEL/DECEL accessory

module (KB P/N 8834) is

available as an option.

It provides separate control

of FORWARD acceleration

and deceleration and

REVERSE acceleration

and deceleration.

B. Dead Band Trimpot (DB) –

The DB trimpot sets the

amount of main speed

potentiometer rotation or

analog voltage input

required to initiate control

voltage output. It is factory

adjusted to approximately

25% of rotation.
The DB trimpot also determines the amount of delay that will occur before

regeneration starts. Regeneration occurs when the applied load torque is in the

same direction as the motor rotation.

To readjust the DB to factory setting:
i. Set Main Speed pot to zero speed position.
ii. Set DB trimpot to full CCW position.

iii. Adjust DB trimpot CW until motor hum is eliminated. (See fig. 19, p. 27 for

graphic illustration of the DB trimpot.)

Note: If the dead band trimpot is set too

low (CCW direction), the motor may oscillate between forward and reverse.

Adjust dead band trimpot CW until the instability disappears. (Oscillation may

also occur due to RESP and IR COMP trimpot settings. See sec. VII, D & F on

page 29.)

C. Forward Current Limit (FWD CL) and Reverse Current Limit (REV CL)

Trimpots – These trimpots are used to set the maximum amount of DC current that

the motor can draw in both the forward and reverse directions. The amount of DC

current determines the amount of maximum motor torque. They are factory set at

150% of the current established by the jumper J3 setting.
Readjust the CL trimpot as follows:
i. Turn CL trimpot to MIN (CCW) position. Be sure jumper J2 is in the proper

position approximately equal to the motor DC ampere rating.

ii. Wire in a DC ammeter in series with armature lead. Lock shaft of motor.
iii. Apply power. Rotate CL trimpot quickly until desired CL setting is reached

(factory setting is 1.5 times rated motor current). Be sure control is in forward

direction for FWD CL trimpot adjustment and likewise with REV CL.
Warning! To prevent motor damage, do not leave motor shaft locked for

more than 2 – 3 seconds.
Caution! Adjusting the CL above 150% of motor rating can cause

overheating and demagnetization of some PM motors. Consult motor

manufacturer.

100

CURVE (a): NO DEAD BAND

CURVE (b): MAX. DEAD BAND

100

-100

(%)

SPEED