Tweco 400 MST Arc Master User Manual

Page 48

400MST

ADVANCED TROUBLESHOOTING

9 – 11

1.4.2 Verification of the Power Input

Circuitry

1) Verify the AC input voltage using an AC volt-

meter

Verify input voltage (Phase-to Phase) using an

AC voltmeter. (The capability of the voltmeter

should be more than 600VAC). Measure the

point between lines U1 and V1 on the input

switch, S1.
Measure the point between lines U1 and W1

on the input switch, S1. Measure the point

between lines V1 and W1 on the input switch,

S1.
The location of points U1, V1 and W1 on switch

S1 are indicated in Figure 9-1.
When using a single-phase connection, the

voltage can be verified only between U1 and

V1.

Figure 9-1: Check points U1, U2, V1, V2, W1 and W2

2) If the input voltage is out of the operating range

of the unit, which is ±10% (187~253/414~506

VAC) of the rated voltage (208, 230/460V),

verify the available power capacity at the

installed site.
If the input voltage is within the operating

range, recheck the input voltage while welding,

as welding may cause the input voltage to

decrease to a value below the operating range

of the unit.

3) Verify input voltage after the input switch (S1)

using an AC voltmeter. (The capability of the

voltmeter should be more than 600VAC.)

•

Using an AC voltmeter, measure between the

points U2 and V2 on the input switch, S1.

•

Using an AC voltmeter, measure between the

points U2 and W2 on the input switch, S1.

•

Using an AC voltmeter, measure between the

points V2 and W2 on the input switch, S1.

The location of points U2, V2 and W2 on

switch S1 are indicated in Figure 9-1. When

using a single-phase connection, the voltage

can be verified only between U2 and V2.

4) If this voltage is out of the operating range,

which is ±10% (187~253/414~506 VAC) of the

rated voltage (208, 230/460V), replace S1 fol-

lowing the process in section 9.2.4.20.

5) Verify the rectified output voltage of the input

diode, D1 using a DC voltmeter. (The capabil-

ity of the voltmeter should be more than

1000VDC.)
Using a DC voltmeter, measure between the

points 1 (P) [+] and 2 (N) [-] on D1.
Points 1 (P) and 2 (N) are on D1.
See Figure 9-2.
The measured voltage should be approxi-

mately 1.4 times larger than input voltage mea-

sured in #1 above. Replace diode D1 if the

calculated measurement is not within the cor-

responding range (260~360/580~720VDC) fol-

lowing the process in section 9.2.4.23.

Figure 9-2: The check points 1 (P) and 2 (N)

6) Verify bus voltage (the voltage of the electro-

lytic capacitor after rectification) using a DC

voltmeter. (The capability of the DVM

should be more than 1000VDC.)
Using a DC voltmeter, measure between the

output studs C and E on PCB8 (WK-5479),

PCB9 (WK5479), PCB10 (WK-5479) and PCB11

(WK5479).
See Figure 9-2.
The measured voltage should be approxi-

mately 1.4 times larger than the input voltage

measured in #1 above, except when running at

1
2

460V where the bus voltage will be shared across

all boards, ie, each board receiving 0.7 times the
input voltage measured in step 1 above. Replace

diode D1 if the