How a 70 kV HV Bridge Rectifier Is Built & Tested │ AES
- Anil Patil
- Jul 27
- 6 min read
Updated: 2 days ago
A 70 kV bridge rectifier looks unremarkable from the outside — a stack or a board feeding a pair of terminals. Inside it is a set of engineering decisions about insulation clearance, thermal margin and surge tolerance that determine whether the assembly survives years of service in a transformer test set or an ESP transformer-rectifier unit.
Ameet Electro Systems (Nashik, Maharashtra) has manufactured high-voltage rectifier assemblies since 2008. This is what goes into a 70 kV unit, and what the finished specifications look like.
How is a 70 kV HV bridge rectifier built?
A 70 kV bridge rectifier is built by connecting avalanche diodes in series to reach the target reverse-blocking voltage, arranging four such strings into a full-wave bridge, and supporting them either as a clamped disc stack or on a high-voltage PCB substrate. The assembly is then insulated, housed, and electrically verified before dispatch.
The five stages below apply to both constructions. Where they diverge, we say so.
Step 1 — Selecting the diode and calculating the string
The starting point is the reverse voltage rating of the individual element. Our ARE20A HV diode disc is rated 22.5 kV VRRM with a continuous reverse voltage of 20 kV, so reaching a 70 kV working voltage with adequate margin is a matter of series-connecting a calculated number of elements per bridge arm.
String length is a balance, not a maximum. Every element added contributes reverse-blocking capability but also forward voltage drop and stack height. The ARE20A drops a maximum of 31 V at its 1.4 A rated forward current; multiplied across a full bridge, that determines both the thermal load and the achievable output.
For reference, the finished 1BR70P PCB-type assembly carries a VRRM of 210 kV per diode against a 70 kV working rating — a deliberate margin, not a coincidence.
Step 2 — Stacking and clamping, or board assembly
Disc-type. Individual epoxy-moulded discs are stacked in series and clamped to a tin-plated copper bus bar. Clamping pressure is the variable that matters most here: it sets contact resistance across every junction in the string. Undertightened joints create local hot spots that shorten service life long before anything measurable shows up at the terminals. Disc alignment through the stack is checked as the assembly is built up.
PCB-type. The diode string is mounted on a glass-fibre high-voltage substrate. Our 70 kV unit uses a 2× PCB-sheet assembly with copper bus bars at 30 × 6 mm and 25 × 8 mm, fixed with tin-plated M8 nut-bolts. The advantage here is that dielectric spacing is set by the board layout rather than by a clamping operation — so it repeats identically across a production run.
If you are deciding between the two, see our comparison of disc-type vs PCB-type bridge rectifier construction — the choice turns on operating medium and serviceability, not voltage class.
Step 3 — Insulation and mechanical housing
Once assembled, the unit is insulated to maintain adequate clearance and creepage distance for the working voltage, following the insulation-coordination principles in IEC 60664. Clearance is the air path between conductive parts; creepage is the path across a surface. Both have to hold up not just at rated voltage but under the pollution, humidity and temperature conditions of the installed environment.
Housing then protects the assembly mechanically without compromising the clearances the design depends on. Disc-type units terminate in M8 input AC and output +Ve / −Ve connections; the 1BR70P terminates at AH (−Ve), AS1 (+Ve) and two AC terminals.
Step 4 — Dielectric (HiPot) verification
Before an assembly is released, its insulation system and diode string are verified against the intended operating conditions. A dielectric withstand test — commonly called a HiPot test — applies a voltage at or above the rated level for a defined hold time and checks for breakdown or excessive leakage current.
Leakage is the figure worth asking any supplier for. The 1BR70P is specified at 1–5 µA reverse leakage at 25 °C, rising to 50–100 µA at 100 °C. A supplier who cannot tell you the leakage figure at temperature has not characterised the assembly. Ours are on the datasheet, and we will send it before you order.
Where a buyer's own quality system sets the acceptance criteria — a specific withstand voltage, hold time, or leakage limit at temperature — tell us at enquiry stage and we will confirm against your specification before the order is placed.
Step 5 — Vibration and functional verification
A bridge rectifier destined for transformer testing or ESP duty has to tolerate mechanical stress and transient surge conditions in service. Our PCB-type bridge rectifiers are vibration-tested by ETDC (Electronics Testing and Development Centre) before dispatch — third-party testing, not a self-declaration. Surge capability is designed in: both the ARE20A disc and the 1BR70P assembly are rated at 50 A IFSM for a 10 ms non-repetitive pulse.
Disc-type assemblies are verified mechanically as they are built — stack alignment and joint integrity are checked through the clamping sequence, because on a clamped stack those are the things that determine whether the electrical characteristics hold up in service.
The finished 70 kV specifications
Both constructions, side by side, from our datasheets:
Parameter | 1BR70P (PCB-type) | 70 kV disc-type |
Configuration | 1-phase full-wave bridge | 1-phase full-wave bridge |
Rated output | 70 kV | 70 kVP |
DC average output (IDAV) | 1.4 A @ Tc 100 °C | 1400 mA |
Construction | 2× PCB-sheet assembly; Cu bus bars 30 × 6 mm and 25 × 8 mm; 4× tin-plated M8 nut-bolts | Stacked epoxy-moulded diode discs screwed to tin-plated Cu bus bar |
Dimensions | 490 × 214 mm | 490 × 195 × 90 mm |
Terminals | AH (−Ve), AS1 (+Ve), AC × 2; M8 | AC in, +Ve, −Ve; M8 nut-bolt |
Operating medium | Air | Oil |
Field serviceability | Replaced as an assembly | Individual discs replaceable |
Applications | ESP, HV power supply | Dust precipitators, X-ray equipment |
1BR70P — full electrical characteristics:
Parameter | Value |
Allowed supply AC voltage (RMS) | 120 kV |
VRRM per diode | 210 kV |
Peak surge (IFSM) | 50 A @ 10 ms |
Forward drop per diode (VF) | 190 V max @ IF 1.5 A |
Reverse leakage (IR) | 1–5 µA @ 25 °C; 50–100 µA @ 100 °C |
Breakdown voltage V(BR)R per diode | 225–330 kV @ IR 100 µA |
Operating temperature | −40 to +125 °C |
Weight | 4.0 kg |
Quality | ETDC vibration tested |
Full datasheets for either configuration are sent on request — tell us the working voltage, output current and operating medium and we will send the one that applies.
What to ask a bridge rectifier supplier
None of the build steps above are visible once an assembly ships. A transformer manufacturer or test-equipment builder evaluating suppliers cannot see clamping pressure or a leakage measurement — so the practical approach is to ask for the numbers that would only exist if the work had been done:
Reverse leakage at operating temperature, not just at 25 °C
The margin between VRRM and the working rating — 210 kV against 70 kV, in our case
What third-party testing the assembly has passed, and by whom
Whether a failed element can be replaced or the assembly is scrapped
The operating medium the unit is rated for — oil or air
Frequently asked questions
How is a 70 kV bridge rectifier verified before shipment?
Its insulation system and diode string are verified against the intended operating conditions with a dielectric withstand (HiPot) test — a voltage at or above the rated level, held for a defined time, checked for breakdown and excessive leakage. PCB-type assemblies are additionally vibration-tested by ETDC. The figures to compare across suppliers are the reverse leakage at temperature: for the 1BR70P, 1–5 µA at 25 °C and 50–100 µA at 100 °C. If your quality system specifies its own withstand voltage or leakage limit, send it with your enquiry and we will confirm against it.
Why does disc-type construction dominate at 70 kV and above?
It does not. AES manufactures both disc-type and PCB-type assemblies at 70 kV and 95 kV. Disc-type is chosen where the unit runs immersed in transformer oil or must be field-serviceable; PCB-type where it runs in air with repeatable geometry. See our disc-type vs PCB-type comparison.
Can a 70 kV bridge rectifier be repaired if one diode fails?
In disc-type construction, yes — a failed disc can typically be identified and replaced without rebuilding the full stack. PCB-type assemblies are replaced as a complete unit.
What is the reverse leakage current of the 1BR70P?
1–5 µA at 25 °C ambient, and 50–100 µA at 100 °C. Both figures are on the datasheet.
Do you also manufacture 95 kV bridge rectifiers?
Yes — the 1BR95P in PCB-type (VRRM 290 kV per arm, 1.4 A IDAV, 640 × 350 mm, 5.3 kg, ETDC vibration tested) and a 95 kV disc-type assembly. Both are on the high-voltage components page.
What is the lead time and shipping term?
Standard lead time is 2–4 weeks from confirmed order. Export shipments are despatched FOB Nhava Sheva (JNPT, Navi Mumbai) with commercial invoice, packing list, and Certificate of Origin (India).
Request a datasheet
Provide:
Working voltage and required output current
Operating medium — oil or air
Space envelope and mounting arrangement
Quantity required
Email: ameetsys@yahoo.com
We respond within one working day with the relevant datasheet and a recommended configuration.
Ameet Electro Systems Plot No. 27, Survey No. 76/2A+B, Someshwar Colony, Satpur MIDC, Nashik – 422007, Maharashtra, India MSME UDYAM-MH-23-0235305 · IEC 3116911487 · GSTIN 27AHZPP6922A1ZY
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