Lumel RP3 Three-Phase Thyristor Power Controller 40-450 A

The Lumel RP3-3-8 is a three-phase thyristor power controller rated 125 A on a 3 x 400 V, 50 Hz load circuit. It switches resistive and resistive-inductive loads without contacts and is built for electric heating: furnaces, extruder barrels, dryers and tube heaters. The same RP3 family covers 40, 70, 125, 200, 300 and 450 A, and the ordering code RP3-3-8 is the example printed by Lumel for the 125 A version without extra quality requirements.

Why thyristor control instead of contactors

A contactor wears when it switches a heater thousands of times, and its on-off action makes the process temperature swing. The RP3 replaces it with thyristors that modulate the power delivered to the load according to the control signal: phase-angle control, impulse (burst) control or simple on-off. The manual lists applications such as annealing and hard-soldering furnaces, crucible furnaces and smelters, plastics extruders, spring winding and tempering, spot and seam welders, infrared drying, glass production and chemical and petroleum preheating and tube-facing heaters.

Key features from the data sheet

• Contactless switching of resistive and inductive loads, up to 450 A in the family.
• Phase, impulse and on-off control, with a choice of impulse, continuous or potentiometric input.
• Soft-start trigger delay, control of the initial trigger angle and load current limitation.
• Trigger stoppage by an external signal.
• Signalling of incorrect phase sequence and of blown fuses.
• Two alarm relay outputs, one for fuse damage, control error or wrong supply connection and one for stop or over-temperature.

Technical specification

Power circuit by current range (manual, Table 2)

Control, supply and environment

Reading the RP3 ordering code

The code has the form RP3 – X – X. The first digit sets the maximum output current: 1 for 40 A, 2 for 70 A, 3 for 125 A, 4 for 200 A, 5 for 300 A and 6 for 450 A, all for a 3 x 400 V a.c., 50 Hz load circuit. The last character is the acceptance test: 8 without extra quality requirements, 7 with an extra quality inspection certificate and X for other requirements agreed with the manufacturer. So RP3-3-8 is the 125 A controller without the extra certificate. Choose the current range with margin above the heater current and size the semiconductor fuses to the table above.

Installation and operation notes from the manual

The IP00 enclosure means the controller is built into a cabinet or a protected enclosure and mounted vertically on a panel. The front carries six status LEDs (supply and readiness, load current, stop, error, over-temperature and fuse failure), three potentiometers for soft start, current limit and span, and a DIP switch for the input type and the control mode. Select the control type with the supply off. Control wiring on the LZ1 terminals takes 0.35 to 2.5 mm2. The fuses of the 40, 70 and 125 A versions are accessible after removing the protective cover. Thyristor heat loss (below 600 W for 125 A) must be removed by cabinet design.

Use in Gulf industrial heating

Heating loads in Omani and GCC plants, such as preheating of pipework, plastics extrusion, drying and furnace lines, run in hot switchrooms. The rated ambient of 0 to 40 degrees C limits where the unit can be installed without cabinet cooling, so allow for the losses and the local ambient when sizing the enclosure.

Frequently asked questions

What does RP3-3-8 mean?

RP3 three-phase power controller, range code 3 (125 A) for a 3 x 400 V load circuit, acceptance code 8 (no extra quality inspection certificate).

Which control signals can the RP3 accept?

Impulse 0/4 to 32 V, voltage 0 to 5 V or 0 to 10 V, current 0 to 20 mA or 4 to 20 mA and a potentiometer of 0 to 10 kohm.

Does the RP3 have a soft start?

Yes. The soft-start time is adjustable from 0 to 10 s for phase or on-off control.

What fuse does the 125 A version need?

The manual lists a 160 (200) A fuse, for example Bussmann 200FEE.

What load types is it intended for?

Resistance and resistance-inductance loads, according to the manual.

Documents and quotation

To buy the Lumel RP3-3-8 through Seven Star LLC, send an enquiry that states the exact code and quantity. We act as an independent supplier in Muscat and reply with delivery time and terms. The Lumel RP3 user manual is attached. It covers wiring, the control types, the fuse table and the ordering codes used on this page; data sheet RP3-19A repeats the ordering example. Read the maker documents first if you need to verify a figure. Related items: Electrical & Power.