BENSHAW RediStart MX3 Series, Руководство пользователя

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SCR Testing
8.5
SCR Testing
8.5.1 Resistance
The SCRs in the starter can be checked with a standard ohmmeter to determine their condition.
Remove power from the starter before performing these checks.
Ÿ
Check from L to T on each phase. The resistance should be over 50k ohms.
Ÿ
Check between the gate leads for each SCR (red and white twisted pair).
The resistance should be from 8 to 50 ohms.
z
NOTE: The resistance measurements may not be within these values and the SCR may still be good. The checks are to determine if
an SCR is shorted "L" to "T" of if the gate in an SCR is shorted or open. An SCR could also still be damaged even though the
measurements are within the above specifications.
8.5.2 Voltage
When the starter is running, the operation of the SCRs can be confirmed with a voltmeter.
Extreme caution must be observed while performing these checks since the starter has lethal voltages applied while operating.
While the starter is running and up to speed, use an AC voltmeter, check the voltage from "L" to "T" of each phase. The voltage should
be less than 1.5 Volts. If the starter has a bypass contactor, the voltage drop should be less than 0.3 volts.
Using a DC voltmeter, check between the gate leads for each SCR (red and white twisted pair). The voltage should between 0.5 and 2.0
volts.
8.5.3 Integral Bypass (RB3)
A voltage check from "L" to "T" of each phase of the RediStart starter should be preformed every 6 months to confirm the bypass
contactors are operating correctly.
Extreme caution must be observed while performing these checks since the starter has lethal voltages applied while operating.
While the starter is running and Up to Speed, use an AC voltmeter; check the voltage from "L" to "T" of each phase. The voltage drop
across the contactor contacts should be less than 300mV. The bypass should be serviced if the voltage drop is greater that 300mV. It
may be necessary to clean the contact tips or replace the contactor.
Built-In Self Test Functions
8.6
Built In Self Test Functions
The MX
3
has two built in self test (BIST) modes. The first test is the standard self test and is used to test many of the basic functions of
the starter without line voltage being applied. The second test is a line powered test that is used to verify the current transformer’s
locations and connections and to test for shorted SCRs/power poles, open or non-firing SCRs/power poles, and ground fault conditions.
8.6.1
Standard BIST Tests
(FUN 22 - Std BIST):
The standard BIST tests are designed to be run with no line voltage applied to the starter. In selected low voltage systems where a
disconnect switch is used, the Disconnect Switch must be opened before starting the standard tests. Standard BIST mode can be entered
by entering the appropriate value into the Miscellaneous Command (FUN22) user parameter.
CAUTION: In order to prevent backfeeding of voltage through the control power transformer (if used), control power must be carefully
applied to the MX
3
control card and contactors so that self testing can occur safely. In low voltage applications, the user must verify that
the applied test control power cannot be fed backwards through the system. “Run/Test” isolation switches, test power plugs, and wiring
diagrams are available from Benshaw.
CAUTION: In low voltage systems with an inline/isolation contactor. Before the inline test is performed verify that no line voltage is
applied to the line side of the inline contactor. Otherwise when the inline test is performed the inline contactor will be energized,
applying line voltage to the starter, and a BIST test fault will occur.
The standard BIST tests comprise of:
Step 1 LCD Display
Go to parameter (FUN22) - misc commands and press [ENTER].
Press [UP] button until it reads "Std BIST" and press [ENTER].
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8 - TROUBLESHOOTING & MAINTENANCE