VMX
2
Series Digital Solid State Soft Starter User Manual
11 |
P a g e
Chapter 3 - Motor Overload Protection
3.1
Solid State Overload Protection
The
VMX2 Series
Starter provides true U.L. listed I
2
t Thermal Overload
Protection as a built-in function of the main digital processor for
maximum motor protection. It mimics the tripping action of a bi-metallic
overload relay, with the accuracy and repeatability of a digital control
system. It is adjustable over a wide range and can easily be
programmed to different trip curves.
3.1.1 Thermal Memory
The
VMX2 Series
mi
croprocessor uses a sophisticated “Thermal
Register” in the digital memory to keep track of motor heating and
cooling over time regardless of the starter’s power status. By using non-
volatile memory, the
VMX2 Series
does not “forget” that the motor has
been running even if power to the starter is turned off and turned back
on. Continuous overload protection is provided based on the true
thermal condition of the motor.
3.1.2 Thermal Capacity
The Thermal Register is displayed as a percentage. This percentage is
the motor’s remaining thermal capacity. The percentage value begins at
100; showing that the motor is cool (has 100% of its capacity available).
As the motor heats up or moves toward an overload condition, the
percentage begins to drop. The Thermal Capacity is derived from the
programmed motor nameplate Full Load Amps (FLA) in Function
F001
,
the Service Factor rating in Function
F002
, and the Overload Trip Class
in Functions
F003
and
F004
. Setting these functions to the proper
values provides maximum protection and eliminates nuisance tripping.
The Remaining Thermal Capacity can be viewed by using the UP or
DOWN arrow keys when in the Status Display mode. From the default
Phase A Current screen (dot on right side), press the UP arrow key 4
times to display
[H100]
meaning there is 100% of the Thermal Capacity
(H = Heat capacity) remaining in the motor. After starting or running, the
motor will use this capacity and the display will show a lower number.
For example, after a cold start, the display may read
[H065]
which
indicates that the motor has 65% of its thermal capacity remaining (35%
used). The Status Display screens cycle back to the beginning, so the
Down arrow keys can access this display as well.
▪
3.1.2.a
Motor Full Load (FLA) Setting
Use Function
F001
to enter motor FLA as indicated on the motor
nameplate. (Do not calculate for service factor, this is programmed
separately in
F002
).
▪
Note:
All
VMX2 Series
starters are shipped from the factory with
F001
set
to a default value of 0000. If
F001
is left at the factory default, the
unit will not operate. If the user attempts to start the
VMX2 Series
without entering the motor nameplate FLA, the starter
will Fault and
the display will read “
nFLA
” (no Full Load Amps).
H100
H057
100% Thermal
Capacity remaining
at rest
57% Thermal Capacity
remaining after starter
(43% used)
Examples:
MOTOR FLA (F001)
must be programmed
for unit to operate!
