Generator brands · Alternators
Mecc Alte Alternator Repairs, from Portable Sets to Standby Machines
From the small single-phase alternator on a portable generator to the three-phase machine on a standby set, we repair Mecc Alte alternators on site in Gauteng. Many small Mecc Alte machines are regulated by a capacitor rather than an AVR, while the larger ones use an electronic regulator, so we identify the machine before testing anything. Then we trace the fault through the regulation, diodes and windings and put it right.
Established 2006
20 years of experience
24/7 operations
We Arrive Within 1–2 Hours
(usually within 1 hour)
Free callouts and quotations
One-year warranty
Qualified and certified technicians
We Service & Repair All Generator Brands
All generator makes and models
1 kVA–20,000 kVA capability
Identify it first
Two kinds of Mecc Alte alternator
Small capacitor-regulated machines
Found on portable and small diesel generators. Many are brushless machines regulated by a capacitor on an auxiliary stator winding, with a diode on the rotor, instead of an electronic AVR. Nothing is adjustable: the voltage depends on the capacitor, the windings and engine speed.
Larger machines with a regulator: AVR repairs
The ECP and larger ECO series, mostly three-phase, on standby and prime sets. These have a brushless exciter, a rotating diode bridge and an electronic regulator that holds the voltage as the load changes.
Why the voltage moves on small and large sets
On a small capacitor-regulated machine the output follows engine speed closely, so a sticking governor or a fuel fault that drops the revs shows up as low voltage. On a three-phase machine the regulator holds the voltage, but an uneven spread of single-phase loads can still leave one phase low, because a regulator with single-phase sensing watches only one phase.
The diagram explains single-phase and three-phase supply in general terms; it is not a Mecc Alte drawing. Our voltage and frequency guide covers what the readings should be.
Low voltage on a small machine: what we check
The same checks apply when a small set runs but gives no output at all.
- Engine speed with no load and on load, because the voltage follows it
- The capacitor, measured against its rating and checked for swelling
- The rotor diode, tested out of circuit
- Main and auxiliary stator winding resistance and insulation
- The breaker, sockets and panel voltmeter, which can fail on their own
A capacitor can hold a charge after the set stops, so testing or replacing it is work for a technician. Fitting an AVR to a machine not designed for one does not fix the fault.
Mecc Alte regulators on three-phase machines
| Regulator | Type | Notes |
|---|---|---|
| SR7 | TypeAnalogue | NotesCommon on small and medium three-phase machines |
| UVR6 | TypeAnalogue, three-phase sensing | NotesUsed where tighter regulation is needed, often on larger machines |
| DSR | TypeDigital | NotesAdjusted with trimmers or through a computer connection; more protection and monitoring |
| DER1 and DER2 | TypeDigital | NotesLater digital regulators with wider configuration |
Which regulator fits depends on the machine, its excitation and its sensing wiring.
Changing a regulator without repeating the fault
Before a regulator is changed we test the exciter field winding, the diode bridge and its surge suppressor, because a shorted diode overloads a new regulator just as it did the old one.
A DSR can replace an SR7 on many machines, but the supply, sensing and exciter field connections must match, and the voltage, stability and under-frequency settings must suit the machine and engine. On a digital regulator we enter settings that suit this alternator and engine, then confirm them by running the set on load.
The under-frequency setting needs care. Below a set frequency the regulator lowers the voltage to protect the exciter and let the engine recover. Set too high, the voltage sags at every small speed dip; set too low, the exciter is overdriven at low speed.
Dust, damp and worn bearings
Small portable alternators work hard in dusty yards and on building sites. Dust clogs the cooling air path so the windings run hot, and a rear bearing that rumbles or runs warm should be changed before the rotor rubs the stator.
Portable sets bought for load shedding often spend months in a garage or shed between outages, and damp gets into the windings. An insulation resistance reading before the set goes back to work tells us if a dry-out will restore it or the stator needs a rewind. Larger standby machines can be fitted with an anti-condensation heater that keeps the windings dry while they stand.
Independent service
We Service & Repair All Generator Brands
Onsite Generator Repairs is an independent generator specialist. We repair, service and maintain Mecc Alte equipment as part of our work on every make of generator.
Manufacturer warranty claims go through the manufacturer’s own network. If your generator is still under warranty, check the warranty terms before arranging work by anyone else.
Brand names and trademarks belong to their respective owners. Onsite Generator Repairs is an independent service and repair company.
Service areas
Where we work in Gauteng
FAQ
Frequently asked questions
My small generator with a Mecc Alte alternator gives low voltage. Does it need an AVR?
If it is capacitor-regulated, no. We check the engine speed first, then test the capacitor, rotor diode and windings.
Can a DSR regulator replace an SR7?
In many cases, depending on the machine, its sensing and wiring. Check with us before buying a replacement, or see our AVR repairs page.
Why does the voltage drop when the engine slows?
Most regulators reduce voltage as frequency falls. If the voltage drops a lot under load, engine speed is often the real problem. See frequency and speed problems.
Is a small Mecc Alte alternator worth repairing?
A capacitor or diode is a modest repair. A burnt stator on a small portable set may cost more than it is worth, and our repair or replace guide helps you decide. We also repair Stamford and Leroy-Somer alternators.
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