Reference Options; Analog Reference - PowerTec 2000C Instruction Manual

Table I is an explanation of the connection and
function of the control circuits of the Brushless DC motor
control. Read the descriptions of the operations of the
circuits carefully, since there are some differences between
the operations in the analog and digital modes.
In some installations there is a temptation to place
a jumper across Emergency Stop terminals, rather than to
install ESTOP buttons. This could set up an UNSAFE
situation. IT IS STRONGLY RECOMMENDED THAT
THE EMERGENCY STOP BUTTON (or ESTOP relay)
BE INSTALLED ON THE 2000C AND 3000C! They
have a ramp stop function which causes the motor control
to decelerate the motor (in the analog mode) to zero speed
before shutting off. (In digital mode, the external frequency
must be reduced to zero for this function.) Even if the
RAMP STOP jumper is removed in a particular installa-
tion, a replacement board or control may be put in at a
later date with the jumper installed, creating a safety
problem. If the Model 2000C does not stop when the
RAMP STOP is pushed, for any reason, the Emergency
Stop is the only way to stop it, short of removing power
from the control.
The motor thermal must be used to adequately pro-
tect the motor from overheating. The motor thermal on the
POWERTEC Brushless DC motor is able to protect the
motor because it is located in the stator windings. Very
little heat is produced in the rotor of the Brushless DC
motor.
Many of the control functions are changed slightly
when the 2000C or 3000C is changed from the analog to the
digital mode. The analog mode uses the analog reference
input (TB2 terminal 10) to set speed. In digital mode they
look for an external frequency at TB1 terminals 11 and 9
(see Section 4.5), and ignore the level of the analog input.
It always looks at TB2 terminal 14 for the direction of
rotation (forward or reverse).
The use of two-wire control between terminals 7 and
4 on TB2 DOES NOT disable the RAMP STOP function.
The only way to disable the RAMP STOP function is to
remove the RAMP STOP jumper.
The RAMP STOP function in the analog mode
shorts the analog reference input to zero, causing the motor
to decelerate to zero speed before shutting off. In digital
mode, the external frequency must be reduced to zero for
the RAMP STOP to function. POWERTEC's DIGIMAX
III takes care of this function when it is installed according
to standard connections, but in other configurations the
system designer must make sure that the frequency goes to
zero. The external frequency may simply be taken away
(such as by the opening of a relay contact), in which case
the 2000C will coast to zero speed and then shut off.
The zero speed output may "chatter" at low speeds,
particularly when the motor is unloaded.
Note that the JOG function OVERRIDES the RUN
function. If the JOG input (+24VDC at TB2 terminal 13)
is activated while in the RUN mode, it will be ignored.
In analog mode, the JOG speed is set by the onboard
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pot (acceleration in current limit), but in digital mode the
speed is set by the external frequency (see Section 5.1.7 for
setting motor direction in Jog). RAMP STOP is active
during the JOG mode, but deceleration time will be deter-
mined by the coast time, since the speed signal from the on
board JOG potentiometer bypasses the accel/decel cir-
cuits. In digital mode, the accel rate is set by the rate of
change of the external frequency, or current limit, if the rate
is too fast. The decel rate in digital mode will be determined
by the coast time (see Section 1-2) if it is longer than the
decel time set.

4.5 REFERENCE OPTIONS

There are options available for speed control of the
POWERTEC Models 2000C and 3000C Brushless DC
motor control. They break down into two types: ANALOG
and DIGITAL. Both types are contained in the basic
control. The selection is made by the application of +24VDC
at TB1 terminal 11 with respect to TB1 terminal 9. This is
an optically coupled input which is not referenced to the
control common.

4.5.1 ANALOG REFERENCE

Analog speed control is the most common type used
for motors and controls. The Models 2000C and 3000C
have positive 10VDC speed references built in. The
reference source is accurate within 1%.
Analog control of speed consists of supplying a 0
VDC (for zero speed) to +10VDC for full speed forward or
reverse. The analog speed signal is applied to TB2-10 with
respect to TB2-12, which is the signal common of the
motor control.
This analog signal might come from a speed poten-
tiometer which is connected to include the use of the
minimum speed pot on the Speed Controller board:
High side of pot
TB2 terminal 9 (+10VDC source)
Wiper of pot
TB2 terminal 10 (reference input)
Low side of pot
TB2 terminal 11 (common)
The speed potentiometer may also be connected for
operation without a minimum speed adjustment:
High side of pot
TB2 terminal 9 (+10VDC source)
Wiper of pot
TB2 terminal 10 (reference input)
Low side of pot
TB2 terminal 12 (common)
Model 2000C / 3000C Manual