2CL2R Power Frequency HV diodes 35KV 100mA 50-60Hz

Rectification Duty

A power-frequency rectifier is designed around a different constraint from a fast-recovery part, and the missing recovery-time figure says so. At 50 or 60 Hz each half-cycle lasts between eight and ten milliseconds; the charge stored in the junction clears in a time so short against that window that it has no bearing on loss, heating or EMI. Putting die area into a fast-recovery structure would add cost without changing anything the circuit sees. Where the design does run at switching frequencies, or fires in short pulses, this is the wrong family and the fast-recovery parts are the ones to look at.

What limits this part instead is forward drop and heat. The forward peak voltage is at least 42 V, and a conducting device at 100 mA turns that into continuous dissipation inside a small epoxy body, which is why the molding compound's thermal conductivity and the surrounding insulation both count as part of the design. The same part sitting in oil sheds heat very differently from one standing in air.

The 35 kV figure appears twice, as repetitive peak reverse voltage and as peak working reverse voltage, so there is no hidden gap between the two names; both are quoted at 25 °C with 2.0 µA of reverse current. Current is specified as 100 mA average under a 50 Hz half-sine wave into a resistive load at a 50 °C break temperature — a defined operating point rather than an open-ended maximum, so a hotter case or a harsher waveform needs margin above it rather than the figure taken at face value.

If your circuit needs more current rather than more blocking voltage, the 30 kV / 150 mA part in the same family carries 15 A of surge instead of 10 A. If the rail only reaches a few kilovolts, a smaller fast-recovery diode will do the job with less bulk.

Product Overview

The 2CL2R is an axial-leaded, epoxy-molded high voltage diode built for one job: rectifying a high voltage rail that starts at a mains transformer. Its ratings are 35 kV repetitive peak reverse voltage and 100 mA average forward current at 50/60 Hz, placing it at the top of the voltage range in our power-frequency family.

Circuits of that shape turn up wherever DC is derived from an AC high voltage source — DC high voltage generators, hipot and insulation test sets, high voltage test transformers and the rectifier chains inside X-ray generator tanks. The diode blocks the reverse half-cycle, conducts the forward half-cycle into the smoothing capacitor or the next stage of a multiplier, and repeats the sequence at line frequency with no recovery penalty to design around.

The body is a black epoxy cylinder with a silver cathode band at one end and two metallic axial leads. The leads can be formed to reach a board, a bracket or a terminal, which is what makes the part usable both in new assemblies and in repair work on existing stacks.

Each rating is quoted together with the condition it was measured under, so the incumbent part in your stack can be compared with this one figure by figure rather than by headline voltage.

Key Features

• Axial leaded connection. The through-hole axial format drops into existing stacks, brackets and hand-soldered assemblies without a board redesign, and it is just as comfortable in wave-soldered production. - High thermal conductivity epoxy molding. Heat leaves the die through the molding compound instead of sitting at the junction, which is what keeps a continuous 100 mA conduction duty stable over a long run. Every part in our axial high voltage diodes range is built the same way. - Low internal resistance. Conduction loss at the rated current stays low, so a device buried in a series string does not add avoidable heat to the assembly. - Special passivation glue chip protection. The chip surface is sealed before molding, holding back the moisture and ionic contamination that push reverse leakage upward in high voltage parts.

Mounting & Insulation

1. Choose the insulation environment before the assembly layout is fixed. Immersion in insulating oil is the recommended route at this voltage, with insulating gas the second choice; both control the field around the leads far better than open air.
2. If the diode lives inside a secondary package or a sealed module, treat the enclosure as part of the thermal design — a closed volume decides how much heat can leave the body, and the parameter margins shrink with it.
3. For exposed-air mounting, add air cooling where you can and keep other metalwork out of the immediate field. A body this small discharges easily across a short path in air.
4. Fit insulated electrodes at both ends when the part runs in air. The lead exits are where the field concentrates on high voltage diodes of this size, and insulating the ends is the simplest way to stop surface tracking.
5. Form and bend the leads before soldering, then clean the body and the lead exits before coating. Adhesive applied over flux residue traps contamination against the surface.
6. Apply the insulating adhesive in a continuous layer around the lead bend and the body end, with no voids or thin spots; that layer carries as much of the shock and tracking duty as the molding does.
7. Re-check the finished assembly at working voltage once the coating has cured. A leakage or partial-discharge check at that stage finds voids while the assembly can still be reworked.

Series Stacking & Cathode Orientation

1. Identify the cathode from the band. The silver band around one end of the black epoxy body marks the cathode, so the lead at that end is the cathode and the plain end is the anode. In a half-wave rectifier the banded end points toward the smoothing capacitor or the load, with the anode toward the transformer secondary.
2. Record the orientation before desoldering. Photograph the existing stack or mark the band position on the bracket first; once the insulating adhesive is applied the band is buried, and the only remaining record of polarity is your own note.
3. Bench-check with a source above the forward drop. Forward peak voltage on this high voltage diode is ≥ 42.0 V, so an ordinary multimeter diode test will not turn it on and can read open on a sound part. Use a supply above that figure with a series resistor to limit current, and confirm conduction in one direction only.
4. Build the string cathode to anode. Above 35 kV, connect two or more devices in series, each anode joined to the next cathode, so every device blocks its own share of the reverse voltage while the forward current passes through the whole chain.
5. Match the devices before you stack them. Reverse leakage runs 2.0 µA at 25 °C and 20.0 µA at 100 °C, and the device with the lowest leakage at a given temperature carries the largest share of the voltage. Keep one string to a single type and, where possible, a single production lot; do not mix a 2CL2R with another voltage class or with a fast-recovery part.
6. Grade the DC share with resistors and the fast fronts with capacitors. A resistor across each diode, sized so its current dominates the 20.0 µA worst-case leakage at 100 °C, holds the DC sharing steady as the parts warm and drift apart. Uneven fast transients are a separate problem, carried by capacitance rather than leakage, so a capacitor across each device evens the front as well.
7. Run each device below its rating. A stack of two 35 kV parts is not a 70 kV rectifier with no margin; keep the per-device working voltage clearly under 35 kV so that imbalance, temperature rise and any single weak device still leave headroom. Oil or gas insulation around the finished string is what makes that margin usable.
8. Confirm every band faces the same way before coating, then recheck at working voltage after cure. A diode fitted the wrong way round in a series string blocks in the conducting direction, heats and fails, and it is the one mistake a coating hides permanently.

Specifications

Insulating Adhesives

• Silicone. Cures to a transparent, elastic rubber that absorbs mechanical shock and rides out severe hot–cold cycling from −40 °C to 200 °C. The safe default when the assembly will see temperature swings or vibration.
• Acrylic. Cures to a transparent, hard coating with low moisture absorption and a fast cure time, plus good wear resistance and insulation. Useful when the assembly has to be handled soon after coating.
• Urethane. Cures transparent and hard, with superior wear resistance and good moisture resistance; it stays stable in low-temperature service but is the weaker choice when the part runs hot.
• Epoxy. Cures very hard and is usually opaque. Strong against moisture, chemical attack and wear, with good dielectric properties — the choice when the coating also has to protect the body mechanically.
• Match the material to the environment. Oil immersion, a sealed module and an air-cooled open mount each ask something different of the layer, and the layer is also what keeps surface leakage on a high voltage diode from creeping up in a damp enclosure.

Ordering & Delivery

1. Send the working voltage, the average and surge current, the operating frequency and the insulation environment the diode will sit in.
2. Add the marking of any part you are replacing if you want the cross-reference confirmed before committing to a quantity.
3. Ask your sales contact about sample availability for an evaluation build, and about the quantity you need for production.
4. Confirm lead time, packing, payment terms and Incoterms with your sales contact when the order is placed.
5. Shipments go by international express, so plan the receiving end for a parcel rather than a pallet.
6. As high voltage diode manufacturers we answer rating, mounting and coating questions from the same contact who handles the order.

Technical Support & Model Matching

Selection starts with your circuit, not a catalogue number: tell us the working voltage, load current, switching frequency and ambient cooling conditions, and our engineers will match a model from our range and explain the margin left in the design. Each model ships with its datasheet, package drawing and installation guide, and we stay available for mounting and soldering questions, start-up checks and fault finding when an existing part runs hot or fails early. Orders run from about 7 days to 6 months depending on quantity, usually by international express.

FAQ