Stellenbosch bottling operators may have spare kW on the PCS display yet little current capacity left on L1. Labelers, coders and office circuits can share that phase with filler and pump demand. MegSolid PMA converters support these unequal phase loads in 80, 105 and 125 kW models, subject to each model’s phase-current limits.
During an outage, the converter carries those branches through the protected board. Size it for the load on each phase as well as the total kW.
MegSolid PMA080, PMA0105 and PMA0125 share a 400 V AC interface and the published 100% single-phase unbalanced-load capability. Compare their AC ratings below:
| MegSolid model | Amandla ombane we-AC amiselweyo | Umbane oqhubekayo oqikelelweyo | Maximum AC current |
|---|---|---|---|
| PMA080 | Amashumi asibhozo kwii-kilowatt | 115 A | 138 A |
| PMA0105 | 105 kW | 150 A | 180 A |
| PMA0125 | 125 kW | 180 A | 216 A |
Phase current can limit a board with spare kW
Successive bottling-line changes can leave a winery’s board with single-phase branches distributed unevenly. An electrician measuring a running line may find L1 importing, L2 near zero and L3 close to export. The aggregate power can still be on target.
The published “100% single-phase unbalanced load” capability allows PMA to operate with unequal phase demand within its electrical limits. It does not put the full 80, 105 or 125 kW on one phase. The proposed load split must stay within the total rating and permitted phase current, with suitable cable and neutral capacity and protection settings.
Record phase current before specifying a larger converter. The single-phase-to-three-phase BESS sizing method covers the branch-allocation review.
PCC measurement and the site’s export rule
Set the EMS export limits against the site’s electricity-distributor requirements.
City of Cape Town distinguishes between grid-tied SSEG with export and with no export. Export requires the City’s bi-directional AMI meter; no-export installations need reverse-power blocking. Inverters connected to the City network must appear on its NRS 097-2-1 approved list, and installation wiring follows SANS 10142-1.
Drakenstein, Stellenbosch, George, Saldanha Bay and other Western Cape municipalities run their own SSEG processes on the same NRS 097-2 series. Eskom-direct plants use Eskom’s embedded-generation route, not the City form.
Commissioning needs to establish whether the EMS controls aggregate three-phase power or reverse power on individual phases. CT location must match that boundary. With a CT on the wrong feeder, the operator may misread L3 flow while the labeling line continues to import on L1.
Incorrect control settings can explain the observed flow even when PCS power is adequate. Set up zero-export control at the PCC with CT placement, the metering boundary and the EMS target matched to the approved connection.
Cape Town’s SSEG feed-in rate sits on the current City tariff schedule and changes with the budget year. Use that schedule if export income is part of the model. Compare export revenue with avoided electricity purchases and the cost of an interrupted bottling run using the site’s bill and production records.
The protected board has to run without grid support
Load-shedding declined during 2025 and 2026, but local outages can still halt a bottling line and delay tanks and scheduled trucks during harvest. Grid-connected operation can hide a phase shortfall because the utility supplies demand beyond PCS output. Once the site separates from the grid, the converter must carry the protected loads within its own phase limits.
MegSolid publishes these PMA specifications:
- 100% single-phase unbalanced load
- 230/400 V off-grid output
- 80 / 105 / 125 kW rated AC power
- on-grid / off-grid switching below 20 ms
- 3% voltage THD with linear load
Lights and control-room circuits on L1 count towards the phase-current limit during backup. Include them and the first load step after transfer in the protected-load assessment. Compare total kW and starting demand with the converter output available at the operating temperature.
MegSolid’s below-20 ms figure covers PCS switching. The site engineer must include detection and changeover time, breaker operation and the load’s ride-through tolerance when designing the grid-tied backup path as a complete system. Testing the transfer with the protected loads connected establishes whether the filler controls and pump starters stay in operation.
Pump-start current needs a separate record from the sustained bottling load. Use the motor-starting PCS sizing method to assess inrush before increasing the converter rating.
PMA selection for running and starting demand
PMA080
Assess PMA080 for a 70–80 kW duty. It has 80 kW AC output, 115 A rated AC current and a 138 A maximum. Maximum DC power is 96 kW. Starting demand or temperature derating may require a larger model even in that load range. Check each phase against its approved current limit; all three models offer the same unbalanced-load function.
PMA0105
Sites with measured duty around 100 kW can assess PMA0105’s 105 kW and 150 A AC ratings. Maximum AC current is 180 A; maximum DC power is 126 kW. This 105 kW energy storage inverter provides more total power than PMA080. Check the most heavily loaded phase before accepting that extra power as sufficient for the site.
PMA0125
Running load or transfer demand may require the 125 kW PMA0125. Its rated AC current is 180 A, maximum AC current is 216 A, and maximum DC power is 150 kW. Apply temperature derating when checking the output available at the installation.
The 400 V board must carry the selected AC current
Upgrading from 80 or 105 kW to 125 kW raises the current the 400 V board must accommodate. Inspect the labeling-line circuits and proposed backup branches for phase current, neutral capacity and switchboard capacity. Correct misplaced CTs before using the measurements to justify a model change.
Sebenzisa i Uqhagamshelo lwe-BESS lwe-400 V kwaye interconnection readiness checks against the selected PMA current class.
PCS ratings under installed operating conditions
MegSolid specifies grid-current THD below 2% on-grid and 98.7% maximum PCS efficiency. Site power-quality measurements must account for VFDs and transformer behaviour at the agreed acceptance boundary. System efficiency also includes battery, cable and auxiliary losses. The test method is covered in the BESS power-quality acceptance test.
MegSolid lists the following overload capability:
- ≤110% continuous
- ≤120% for 2 minutes
- >120% for 200 ms
Confirm the applicable operating limits before using the ≤110% continuous allowance for sustained duty above rated power. Higher overload levels are limited to the published durations and approved conditions.
Integrators can connect the PCS to the BMS and EMS through RS485, CAN and Ethernet. Set EMS priority logic to allocate power and energy between phase demand, backup reserve and zero-export control.
MegSolid specifies an operating range of −30 to +60 °C, with derating above 45 °C, and installation up to 5,000 m, with derating above 3,000 m. The power compartment has an IP20 rating and the control compartment IP6X. Provide a suitable system enclosure for outdoor installation.
Closed containers around Worcester or Robertson can have different heat exposure from plant rooms in coastal Cape Town. Use the intake temperature during the required duty to select output, based on measurements or the site’s design conditions.
Choosing the model from the recorded load
Compare phase records from normal operation and backup against the aggregate or per-phase export target. Those records help distinguish insufficient converter power from uneven load distribution. Keep pump-start demand separate from sustained load, and reserve enough battery energy for backup when the system also shifts solar energy.
| Imeko yendawo | Imveliso kaMegSolid | Why |
|---|---|---|
| Uneven phases, total duty near 80 kW | PMA080 | Lower power class, unbalanced-load support retained |
| Duty around the 100 kW class | PMA0105 | 105 kW rating, same phase capability |
| Total PCS duty needs the higher class | PMA0125 | Rated power rises to 125 kW |
| One phase restrictive, total kW adequate | Keep PCS size under review | Correct distribution first |
| Imbalance only appears after islanding | Review protected-load board | Weak point may be the backup bus |
| Zero-export looks wrong on one phase | Review PCC metering and EMS | Phase handling and export control are separate jobs |
Imibuzo Ebuzwa Rhoqo
What usually unbalances a factory board?
Electricians may find lighting, controls, offices, heaters and small auxiliaries concentrated on one phase, even with balanced three-phase motor loads.
What does 100% single-phase unbalanced load mean on PMA?
The PCS can keep running with unequal phase demand. Total rating and phase-level electrical limits still apply.
Can PMA080 handle an unbalanced bottling hall?
Yes, provided the load meets the approved total-power and phase-current limits, including starting demand and temperature derating. MegSolid includes the unbalanced-load function in all three PMA models.
When is PMA0105 the better fit?
Assess PMA0105 for converter duty around 100 kW, with phase current and operating conditions within the approved limits.
When does PMA0125 become justified?
Select PMA0125 where the total-duty assessment requires that power class. Check L1 at its highest recorded load against phase-current and distribution limits before increasing PCS size.
Can one phase import while another exports?
Yes. An operator can record import on one phase and export on another with the three-phase total close to target.
What should be checked when phase flows look wrong at the PCC?
Check CT placement, the metering boundary and EMS target before attributing the flow to PCS size. Confirm whether City of Cape Town, another municipality or Eskom supplies the site.
Why does backup expose a phase problem that grid-tied running hides?
The utility supplies phase demand beyond PCS output during normal operation. After separation, the PCS has to carry the full load split on the protected bus.
Does PMA’s below-20 ms switching mean a below-20 ms outage at the load?
MegSolid’s figure covers PCS switching time. The installer must assess the full interruption at the load, including detection and transfer equipment.
Is 98.7% the round-trip efficiency of the complete BESS?
MegSolid specifies 98.7% as maximum PCS efficiency. Calculate complete BESS round-trip efficiency across the agreed system boundary.
Can overload replace a larger continuous rating?
Use the approved continuous limit for sustained duty. The published ≤110% entry specifies continuous operation; ≤120% has a two-minute limit and >120% a 200 ms limit.
Can PMA be installed outdoors as supplied?
The power compartment is IP20. Outdoor plant needs a suitable system enclosure.
Do City of Cape Town and Eskom use the same export rule?
No. Confirm the distributor, the SSEG or embedded-generation approval, and whether the site is export or reverse-power blocked before setting EMS limits.