Tweco 186 DC Inverter - Manual (Page 73)

SERVICE 186 AC/DC INVERTER
Manual 0-5237 5-3 POWER SOURCE PROBLEMS AND ROUTINE SERVICE REQUIREMENTS
A. Testing Schedule
1. For transportable equipment, at least once every 3 months; and
2. For fixed equipment, at least once every 12 months.
The owners of the equipment shall keep a suitable record of the periodic tests and a system of tagging, includ-
ing the date of the most recent inspection.
A transportable power source is deemed to be any equipment that is not permanently connected and fixed in
the position in which it is operated.
B. Insulation Resistance
Minimum insulation resistance for in-service Thermal Arc Inverter Power Sources shall be measured at a volt-
age of 500V between the parts referred to in Table 5-2 below. Power sources that do not meet the insulation
resistance requirements set out below shall be withdrawn from service and not returned until repairs have
been performed such that the requirements outlined below are met.
Components to be Tested
Minimum Insulation
Resistance (MΩ)
Input circuit (including any connected control circuits) to welding circuit
(including any connected control circuits)
5
All circuits to exposed conductive parts 2.5
Welding circuit (including any connected control circuits) to any auxiliary
circuit which operates at a voltage exceeding extra low voltage
10
Welding circuit (including any connected control circuits) to any auxiliary
circuit which operates at a voltage not exceeding extra low voltage
1
Separate welding circuit to separate welding circuit 1
Table 5-2: Minimum Insulation Resistance Requirements: Thermal Arc Inverter Power Sources
C. Earthing
The resistance shall not exceed 1Ω between any metal of a power source where such metal is required to be
earthed, and -
1. The earth terminal of a fixed power source; or
2. The earth terminal of the associated plug of a transportable power source
Note that due to the dangers of stray output currents damaging fixed wiring, the integrity of fixed wiring sup-
plying Thermal Arc welding power sources should be inspected by a licensed electrical worker in accordance
with the requirements below -
1. For outlets/wiring and associated accessories supplying transportable equipment - at least once every
3 months; and
2. For outlets/wiring and associated accessories supplying fixed equipment - at least once every 12 months.
D. General Maintenance Checks
Welding equipment should be regularly checked by an accredited Thermal Arc Service Provider to ensure that:
1. Flexible cord is of the multi-core tough rubber or plastic sheathed type of adequate rating, correctly
connected and in good condition.
2. Welding terminals are in suitable condition and are shrouded to prevent inadvertent contact or short
circuit.
3. The Welding System is clean internally, especially from metal filing, slag, and loose material.