The AVTRON MODEL LPH400 RESISTIVE LOAD BANK (Part Number LPH400D43233) is a portable, self-contained industrial test unit designed primarily for indoor use, specifically for electrically loading and testing generators. Its core function is to dissipate electrical energy, transforming it into heat via resistor elements, which is then removed by a cooling fan.

Function Description:

The LPH400 Load Bank is rated at 400 kW at 240/480 volts. It provides a balanced load for 3-phase generators within this voltage range. Available load steps include 100 kW, 100 kW, 100 kW, 50 kW, 25 kW, 10 kW, 10 kW, and 5 kW, all selectable via toggle switches on the control panel. For single-phase loads, the unit provides 2/3 of the normal 3-phase load. The fan motor is a 3 HP, 3-phase motor operating from 208-230/460 volts, 3-phase, 60 Hz power. It can be powered either from the generator under test (connected to the Load Bank main load bus) or from a remote external source. When operating from the generator, the motor circuit automatically configures for high or low voltage. The unit is capable of testing 240/480 volt, 3-phase, 60 Hz generators without wiring changes. It can also be used for 60 Hz, 50 Hz, or 400 Hz generators, though for 50 Hz or 400 Hz generators, the fan motor and control circuit power must be supplied by separate 60 Hz sources. Control power is 115 VAC, 60 Hz, supplied by an integral 240/480V to 115V control transformer.

Safety features are integrated to protect both the equipment and operators. Fan failure protection is provided by a differential pneumatic pressure air switch (S51) that senses airflow. An additional slave relay (K30) activates when power is applied to the fan motor terminals and will disconnect control power to all load contactors if fan power is lost, the motor overload trips, or air inlet screens become blocked. This ensures that the load bank never operates without adequate cooling airflow, preventing resistor element overheating and potential fire hazards. The unit is safety checked for opens, shorts, and insulation integrity, with all fuses, safety interlocks, and related safety equipment tested during manufacturing.

Usage Features:

The Load Bank features a control panel mounted behind a sliding door, which can also be integrated into a 19-inch rack enclosure. This panel houses all necessary switches for operation, including full digital metering that displays volts, amps, and kW with individual phase selection. A switch (S7) on the control panel allows switching between high (480V) and low (240V) voltage configurations for the load. The fan motor configuration also changes automatically when powered from the generator under test, with separate overload protection for high and low voltage operation. A voltage protection circuit safeguards the system against improper voltage modes.

Operators must read the manual before use and ensure an approved ground conductor wire is connected from the Load Bank ground point and the generator frame to a good earth ground. The airflow switch must not be bypassed, as it is crucial for safety. Blown fuses should not be bypassed; the cause of the blown fuse must be determined and corrected. Burned-out bulbs on the Control Panel should be replaced promptly as they indicate system status or failures.

The Load Bank requires a 115V, single-phase, 60 Hz, 15 amp source for its control circuit, typically supplied by the integral control transformer using the generator output. If internal power for the motor and control is not desired, an external power source can be used. During startup, the load switch on the generator under test should be OFF until the prime mover brings the generator up to speed, and it should be turned OFF before generator shutdown procedures.

For remote fan power operation (e.g., when testing single-phase systems or non-60 Hz frequencies), the fan motor must be run from a separate source. The control panel selector switch must be set to match the external voltage, and the external fan power source connected to terminals 1 through 3 of TB2 in the customer load connection compartment. When operating at 50 Hz, the motor speed is reduced, which also reduces cooling capacity; therefore, input bus voltages should not exceed 400 volts in 480 mode or 200 volts in 240 mode. The fan motor should not be operated at 400 Hz.

Load connection involves connecting a 240/480 volt, 3-phase source to the three fused bars (A, B, and C) in the customer connection access box. Cables must be sized according to the National Electric Code. For single-phase generators, power cables connect to Phase A and Phase C bus bars. The "B" bus and any attached wiring are electrically live during single-phase operation. A permanent ground connection to the Load Bank enclosure is required.

Operating instructions include placing all control panel switches in the OFF position, setting the BLOWER VOLTAGE SELECT switch to the correct voltage and source, and setting the LOAD VOLTAGE SELECT switch to the correct generator test voltage. The CONTROL POWER INTEGRAL XFMR 240V/480V selector switch must match the generator voltage. After starting the generator and stabilizing it, the BLOWER START pushbutton is pressed. The red BLOWER FAIL lamp will light momentarily until sufficient airflow is detected. If it stays on, the unit should be shut down and the problem corrected. The MASTER LOAD ON/OFF switch connects power to all selected load steps. Load steps can be added or removed while the MASTER LOAD switch is ON. After testing, the MASTER LOAD switch is moved to OFF, and the fan motor should be allowed to operate for about 5 minutes to cool the elements and exhaust residual heat, preventing burn injuries.

Maintenance Features:

Regular maintenance is crucial for equipment longevity and safety. All maintenance work must be performed by qualified personnel. An initial inspection upon receipt and periodic preventive maintenance are recommended.

Daily maintenance includes removing any airflow restrictions, checking screens for blockages or damage, verifying correct airflow direction, and ensuring no exhaust air recirculation.

Every three months or 500 hours, more detailed inspections are required. This involves removing access panels and screens to inspect load resistors for sagging elements, replacing them as needed. Ceramic insulators should be inspected for cracks and replaced if found (minor chips less than 1/8" diameter are acceptable). Loose hardware and connections should be tightened, and oxidized or corroded connections cleaned or replaced. The airflow switch's proper function must be verified. Contactors should be inspected for severe pitting or corrosion, ensuring they move freely and seat properly. The Load Bank interior should be cleaned of dirt and debris using clean, dry compressed air (not exceeding 40 PSI), with eye protection worn. All wiring should be inspected for insulation failure, especially near resistor case sheet metal or element support rods. Current transformers should be handled with care; if defective, all leads must be marked before removal to ensure proper phasing during replacement. Connections should be inspected for signs of heat stress, indicating loose hardware or corrosion, and repaired or replaced as necessary.

A critical warning is issued regarding current transformers: the secondary of an unshorted or unshunted current transformer can generate thousands of volts, posing a risk of harm to personnel or damage to the C.T. and related instruments. It is essential to verify that no primary current is flowing through the C.T. and that all C.T. leads are properly terminated.

After maintenance, all access panels and screens must be replaced and fastening hardware securely tightened. Indicator lamps on the control panel should be checked and replaced if necessary.

Annually, the blower motor must be lubricated according to the motor manufacturer's requirements and specifications found on its nameplate.

For parts replacement, access to components is facilitated by removable cover panels. A Replacement Parts List, including descriptions, quantities, Avtron part numbers, and schematic reference designators, is provided to assist service personnel. When ordering parts, the part's description, Avtron part number, schematic reference designator, and the equipment's model and serial number should be provided. Avtron maintains an inventory of commonly used items.

The Load Bank should be stored in a dry, enclosed area and covered to limit moisture and dust accumulation. An optional waterproof vinyl cover is available, but permanent outdoor storage is not recommended even with the cover.

Avtron LPH400 - Page 18

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