PowerTec Regenerative Brushless DC Motor Control 1000AR - Manual (Page 40)

Model 1000AR Installation and Operation Manual P AGE
39
OFFICIAL 6/4/2001
WHAT HAPPENS WHEN I …
SLO W DO WN O R O VERHAUL THE M O DEL 1000AR ?
Since the Model 1000AR is a regenerative drive (see page 3), the motor does not coast when the
speed reference is reduced. The deceleration ramp is enforced by removing energy from the motor. This
is accomplished by treating the motor as a generator and applying a load to it.
A non-regenerative drive coasts when the
motor speed exceeds the commanded
speed. The drive cannot force the motor to
slow down. The non-regenerative drive will
enforce the deceleration ramp time ONLY if
the decel ramp time is greater than the
natural coast time of the motor and load.
The regenerative drive (Model 1000AR) can enforce the decel ramp time at any regenerative load up
to its Regenerative Current Limit (RCL) setting. If the inertia of the load is greater than can be slowed by
the motor at regen current limit, or if the motor is being overhauled by another motor, the drive will
continue to apply the current limited value of torque, but the drive will lose speed control. The motor and
load will then slow down according to a modified coast time curve.
When you started up, you probably turned the RCL pot on the Speed Controller board down to the
fully counter-clockwise position. The first time you turn down the speed pot, you should see a RED
REGEN LED and a RED CURRENT LIMIT LED, but the motor may appear to be coasting. Turn the RCL
pot clockwise to about 50% and bring the motor up to a high speed again.
Now, when you turn the speed pot down (it does not need to be zero; it can be any new, lower
speed), the REGEN LED should light, but the CURRENT LIMIT LED may or may not come on. If the coast
time is much greater than the decel time, the drive may reach current limit. Whether or not current limit will
be reached can be predicted, but you need to know all the drive and motor data and all of the inertias
involved in the system to do so. The maximum (CW) setting of the RCL is equivalent to 150% of full load.
You should also see a RED LED on the bus loader flicker to show it is operating and the regenerative
resistors will get warm (for small or quick changes in speed) or hot (for longer regenerative intervals.
Since the regenerative mode is active only when the motor speed exceeds the commanded speed,
the REGEN LED will be on only during the deceleration period. Once the motor gets to the new speed,
regen shuts off and the drive returns to normal operation. If you are reversing the direction of the motor,
the REGEN LED will only stay on until the motor stops.
If the motor speed is being increased by an outside force pulling on it (overhauling load), the REGEN
LED will come on and stay on. The drive will attempt to hold the commanded speed by regenerating, up to
a maximum of its RCL setting. In any case of an overhauling load, you must be careful not to exceed the
rated capacity of the regenerative resistors.
If continuous regeneration is expected, and the overhauling load is caused by another motor, you
may want to consider using a “common bus” configuration. A common bus configuration requires another
BLDC drive which is ALWAYS in motoring mode while the regenerative unit is regenerating. This is the
case if the common bus motoring motor is doing the overhauling which is causing the regeneration of the
common bus regenerating motor.
NON-REGEN DRIVE
REGEN DRIVE
DECEL TIME
RUNNING SPEED
NEW SPEED
(may be zero)
REGEN