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Solid-State Starters — Troubleshooting guides per-

taining to the operation of the solid-state starters may be found

in Fig. 49-55 and Tables 13 and 14.

Attempt to solve the problem by using the following pre-

liminary checks before consulting the troubleshooting

tables.

When the power is off:

• Inspect for physical damage and signs of arcing, overheat-

ing, etc.

• Is the wiring to the starter correct?

• Are all connections in the starter tight?

• Is the current feedback resistor properly adjusted and

installed?

• Is a heater coil installed in each leg of the motor?

• Is the control transformer fuse blown?

• Is the motor connected to the starter?

TESTING SILICON CONTROL RECTIFIERS IN BEN-

SHAW, INC. SOLID-STATE STARTERS — If a silicon con-

trol rectiﬁer (SCR) is suspected of being defective, use the

following procedure as part of a general troubleshooting guide.

IMPORTANT: Before performing the SCR check be-

low, remove power from the starter and disconnect the

motor terminals T1, T2, and T3.

1. Connect ohmmeter across terminals L1 and T1. Resis-

tance reading should be greater than 50,000 ohms.

2. If reading is less than 50,000 ohms, remove connecting

bus heatsink between SCR3 and SCR6 and check anode

to cathode of SCR3 and SCR6 separately to determine

which device is defective. See Fig. 49. Replace defective

device and retest controller.

3. Repeat Steps 1 and 2 across terminals L2 and T2 for SCRs

2 and 5.

4. Repeat Steps 1 and 2 across terminals L3 and T3 for SCRs

1 and 3.

If the SCRs tested were not defective but the problem

still persists, refer to the following Steps 5 and 6.

5. Disconnect the SCR1 from the white gate and red cath-

ode wires on the control logic card BIPCRS6. With an

ohmmeter set on Rx1, check between white and red wires.

Resistance should normally be between 8 and 20 ohms

average. Excessively high or low resistance may be in-

dicative of a defective device. Replace and retest.

6. Repeat Step 5 for SCR leads 2 through 6. Care should be

taken to ensure that the gate and cathode wires are re-

placed exactly as they were: white wire to gate

(G1 through G6); red wire to cathode (K1 through K6).

Damage to the starter may result if wires are

reversed.

If problem is still not resolved, consult the starter manu-

facturer for servicing.

TESTING SILICON CONTROL RECTIFIERS (SCRs) IN

CUTLER-HAMMERt SOLID-STATE STARTERS — To

check for a shorted SCR refer to Steps 1-3 and

Fig. 50-53.

NOTE: Do not megger (high voltage insulation test) the starter.

1. Connect ohmmeter across terminals L1 and T1. Check

the resistance reading. Resistance reading should be greater

than 10,000 ohms.

2. Connect ohmmeter across terminals L2 and T2. Check

the resistance reading. Resistance reading should be greater

than 10,000 ohms.

3. Connect ohmmeter across terminals L3 and T3. Check

the resistance reading. Resistance reading should be greater

than 10,000 ohms.

If the SCRs tested were not defective, but the problem

persists, refer to Steps 4-8.

4. Connect the T1, T2, and T3 terminals on the starter to the

motor.

5. Disconnect one of the wires to the shunt trip contact on

the starter. This wire is disconnected to prevent the shorted

SCR detection from operating the disconnect device while

this test is being performed.

6. Close the disconnect breaker. Check the voltage from the

starter line terminal to load terminal on each phase. The

measured voltage should be approximately 0.58 times the

system line-to-line voltage. If the voltage on any power

pole is signiﬁcantly less, one or both SCRs in the power

pole may be shorted. See Fig. 51.

7. If a shorted SCR is detected, check for possible shorted

connections, system grounds, or any other condition that

might be causing the short. Replacement of SCRs or power

poles without determining the cause of the failure may

result in repeated failure of the SCRs.

8. When the starter is running, measure the voltage from the

line side to the load side of each starter power pole. The

voltage should be approximately 1 to 1.5 vac.

When measuring voltage from line side to load side, ob-

serve proper electrical safety procedures since the power

poles have voltage applied. This voltage could be as high

as 600 v. Personal injury could result.

If one of the voltages is higher than 2 v, but the voltages

of the 3 power poles are approximately equal, the starter is

probably still in current limit. If the voltage is higher than

2 v on only 1 or 2 power poles, not all SCRs are ﬁring prop-

erly. Make sure the gate lead connections are tight. If all 3

power poles have less thana2vdrop from line side to load

side of each starter power pole when the motor is up to speed,

any current unbalance in the motor is caused by the motor

or an unbalanced line voltage.

SCR — Silicon Control Rectiﬁer

Fig. 49 — Typical Benshaw, Inc. Solid-State Starter

(Internal View)

1 2 ... 78 79 80 81 82 83 84 85 86 87 88 ... 103 104

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