How to Choose a Generator for Your Workshop — 7 Steps for NE India

Written by the counter team at Multi Trade Combines — 33 years supplying NE workshops.

Power outages strike at the worst moments — mid-weld, mid-cut, mid-pour. This checklist is what our counter team works through with every workshop owner who walks in asking about generators. Follow each step in order.

Step 1 — List Every Load You Need to Power

1. Write down every machine and appliance that may run simultaneously: welding machine, angle grinder, drill, concrete mixer motor, lighting, fan, battery charger.
2. Note the rated wattage (W) or kVA of each item. This is on the nameplate or in the manual. For motors, use the kW figure — not the HP rating alone (1 HP = 0.746 kW).
3. Identify which loads run at the same time and which are used one at a time. A welding machine and an angle grinder are rarely running simultaneously; a workshop light and a fan always are.
4. Add a 25% safety margin to your total simultaneous load. This headroom protects the generator from overload and extends engine life.

Example — a typical fabrication workshop in Guwahati: 200A inverter welder (4 kVA) + angle grinder (1 kVA) + 4 tube lights (0.2 kVA) + fan (0.1 kVA) = 5.3 kVA running load. With 25% margin: 6.6 kVA. Choose a 7.5 kVA generator.

Step 2 — Account for Starting Surge (Motor Starting kVA)

1. Electric motors (concrete mixer, pump, compressor) draw 3 to 6 times their running current for the first 2–3 seconds on start-up. This starting surge is the most common cause of generator overload and engine stall.
2. For a 1 HP (0.75 kW) motor with a 5× starting surge: peak demand = 3.75 kW during starting. Your generator must handle this peak even if the running load is low.
3. If your workshop runs a concrete mixer or air compressor alongside a welder, size the generator to the starting surge of the largest motor — not just running wattage.
4. Inverter welders have very low starting surge — they are the easiest load for a generator. Resistive loads (heaters, lights) have no surge. Induction motors have the highest surge.

Step 3 — Choose Petrol or Diesel

Step 4 — Confirm AVR and Voltage Regulation

1. Always choose a generator with AVR (Automatic Voltage Regulator). Without AVR, voltage swings with load changes — damaging inverter welders, VFDs, electronics and UPS systems.
2. Look for a stated voltage regulation of ±5% at rated load. Better generators achieve ±3%.
3. For sensitive equipment (digital measuring instruments, CNC controllers, computer-controlled welders), a pure sine wave inverter generator is preferable over a conventional AVR generator — it produces cleaner power with lower total harmonic distortion (THD).
4. NE India tip: voltage from the grid in many areas swings between 180 V and 250 V. Your generator output should be steadier than the grid. If your generator's AVR is not maintaining 220–230 V, pair it with a servo voltage stabiliser for critical equipment.

Step 5 — Check Generator–Welder Compatibility

1. Only use IGBT inverter welding machines with generators. Older thyristor (SCR) or transformer welding machines are sensitive to generator frequency variation and may produce erratic arcs or trip the generator on starting surge.
2. Size the generator at a minimum of 2× the welder's kVA draw — and preferably 2.5× for comfortable operation. Running a generator near 100% load continuously shortens engine life.
3. The Alpha A2200 petrol generator (2.2 kVA) is suited for running power tools and lighting on remote sites — it is not sized for welding machines. The Swift Pro SW3600 (3.6 kVA) can run a small 140–160A inverter welder for light work. For a full 200A welder, a 5–7.5 kVA unit is the minimum.
4. Do not run multiple power tools and a welder from one small generator simultaneously. The combined starting surge will stall the engine.

Step 6 — Evaluate Runtime and Fuel Tank Capacity

1. Calculate fuel consumption: petrol generators typically consume 0.4–0.6 litres per hour per kVA of load. A 5 kVA generator running at 70% load consumes roughly 1.5–2 litres/hour.
2. Match tank capacity to your working shift. A 15-litre tank at 2 litres/hour gives 7.5 hours — a full working shift without refuelling.
3. For remote sites in the Northeast (hill districts, forest areas, border areas), factor in fuel availability. Diesel stations are fewer and farther in Arunachal, Nagaland and Mizoram — plan your fuel carry.
4. For standby use in Guwahati (power cuts of 2–4 hours), a 5-litre tank on a petrol generator suffices. For full-shift standby at a fabrication workshop, diesel with a 25–50 litre tank is practical.

Step 7 — Plan for Maintenance and Spare Parts

1. Service intervals for petrol generators: oil change every 50–100 hours, spark plug every 200 hours, air filter cleaning every 50 hours. Diesel: oil change every 150–200 hours, fuel filter every 500 hours.
2. Source your generator from a dealer with spare parts availability in NE India. Obscure brands may be cheap but have no service network — the nearest spare may be in Delhi.
3. Keep at minimum: spare spark plug(s) (petrol), spare engine oil (correct grade), spare air filter element, and spare fuses for the panel. These can mean the difference between a 5-minute fix and a lost workday on a remote site.
4. Check the generators catalogue for models we stock with available local support.

Related Products

• Alpha A2200 Petrol Generator
• Swift Pro SW3600 Generator
• Generators Catalogue

Frequently Asked Questions