Example 5. How To Use The Start-Up Time Counter - ABB SPAM 150 C Technical Information

Example 5
How to use the
start-up time
counter
Quite often a motor manufacturer gives a state-
ment of how many times a motor may be re-
started within a certain time interval. The start-
up time totalling check acts as a backup to the
thermal protection by keeping track of that re-
starts cannot be made too frequently, in other
words that the recommendations from the
manufacturer are not exceeded.
The start-up time counting possibility is inte-
grated in the module SPCJ 4D34 so that no
extra timers are needed. To use the start-up time
counter, two settings must be worked out. First
we must define the restart inhibit level in start
seconds and further we must tell the module
how rapidly the accumulated amount of start
seconds should be counted down.
Let us for example assume that our motor is
recommended to be started at the most for three
times within 8 hours and that the start-up time
is 20 seconds each. By making all the allowed
three starts in a row we will get the situation
described in the diagram below.
∑ts
[s]
50
Start 3
40
30
Start 2
20
Start 1
10
0
Figure 11. The operation of the start-up time counter.
The three 20 second starts add up to a total of
60 seconds. Right after the third start has been
initiated, the inhibit should be activated as a
fourth start attempt is no more allowed. This
means that the setting of the inhibit level in this
case is set at 41 seconds. Please note that the
start sequence will still proceed even though the
inhibit is activated. The inhibit is only inter-
rupting the close path to the circuit-breaker, thus
preventing further start-ups.
Furthermore the statement of not more than
three starts within 8 hours means that the count-
down should reach the inhibit level after 8 hours
to allow for a single new start. In our example
this means that we should count down 20 sec-
onds in 8 hours, i.e. the countdown rate setting
is ∆∑ts/∆t = 20 s / 8 h = 2.5 s / h.
Please note that for readability reasons, the time
scaling in the diagram is not the same for the
start-up versus cooling-down sequences!
8 h
Next start possible
Restart inhibit activated above 41 s level
t
15