Motor Starting Methods: DOL vs Star-Delta vs Soft Starter vs VFD (with Parts & Prices)

DOL is the simplest and cheapest starter but draws about 6–8 times full-load current; star-delta cuts that to roughly one-third for delta-rated motors; a soft starter ramps the voltage; a VFD starts at about full-load current and also controls speed. For a 10 HP motor, the DOL contactor and overload relay cost about ₹3,230 on Voltkart, and a 10 HP Delta VFD ₹28,500.

By Team Voltkart · Reviewed by Amit, Voltkart · Last updated 6 October 2026 · Prices checked 6 October 2026

The four starting methods compared

What is a DOL starter and when is it enough?

A direct-on-line (DOL) starter connects the motor straight to the full supply through a contactor, with an overload relay or an MPCB for protection. It is the simplest, cheapest and most reliable method and gives the motor its full starting torque. The drawback is inrush: the motor typically draws about six to eight times its full-load current for a few seconds, which can dip the supply, trip upstream breakers or shock belts and couplings. DOL is the normal choice for small motors and wherever the supply is strong enough to take the inrush. Many sites and utilities expect a reduced-current starting method above a certain motor size, so check the local requirement for larger motors. For a typical 10 HP (7.5 kW) motor at 415 V with a full-load current of about 15.5 A, a DOL starter needs an 18 A contactor such as the LC1E1810 (₹1,400) or LC1D18 (₹1,857) and a 12–18 A overload relay (LRE21 ₹1,830 or LRD21 ₹2,200), or a GV2ME20 MPCB (₹5,850).

How does a star-delta starter work?

A star-delta starter starts the motor with its windings connected in star, so each winding sees the phase voltage (about 58% of line voltage) instead of the full line voltage. Starting current and starting torque both fall to roughly one-third of their DOL values. After a set time, a star-delta timer switches the windings into delta and the motor runs at full voltage. It needs a motor designed to run in delta at the supply voltage (in India, a 415 V delta motor with six terminals), three contactors (main, delta and star), an overload relay and a star-delta timer. Because torque is reduced to about one-third, it suits loads that start lightly, such as centrifugal pumps, fans and unloaded compressors, but not loads that must start under full load. There is also a short current peak at the star-to-delta changeover, which a correctly set timer keeps small.

How do you size a star-delta starter?

In a star-delta starter, the main and delta contactors carry the winding current, which is about 58% (1/√3) of the motor's full-load current, and the star contactor carries about 33%. The overload relay is usually placed in the main (winding) circuit and set to about 58% of the full-load current. For a 10 HP motor with 15.5 A full-load current that means about 9 A for the main and delta contactors, about 5 A for the star contactor and an overload relay set to about 9 A. Three 9 A contactors such as the LC1E0910 (₹1,056 each), a 7–10 A LRE14 relay (₹1,650) and a Selec 800SD-2-415 star-delta timer (₹810) cost about ₹5,628 together, before the enclosure, MCB and push buttons. Other timers: Selec 800SD-2-230 (₹680) for a 230 V control circuit and EAPL B1DS (₹1,590).

Soft starter vs star-delta: which is better?

A soft starter gives a smooth, stepless start and a soft stop, works with any motor connection and lets you adjust the starting current, so it avoids the changeover current peak of star-delta and the water hammer that a sudden stop can cause in pumps. A star-delta starter is cheaper, made from standard contactors that any electrician can service, and adds no electronics, but it needs a six-terminal delta motor and gives only about one-third starting torque in a single fixed step. For a fixed-speed pump or fan with a delta motor, star-delta is the economical choice; where the start must be smoother, or the motor cannot be wired star-delta, a soft starter or a VFD is better. Voltkart stocks star-delta parts and Delta VFDs but not soft starters; the full comparison is in VFD vs soft starter.

When is a VFD the right starter?

A VFD is the right choice when the load benefits from speed control, needs high torque at a low starting current, or must run a three-phase motor from a single-phase supply. It starts the motor with current close to full-load current, so it suits weak supplies and generator sets, and on pumps and fans it saves energy whenever the speed can be reduced. A 1 HP single-phase input Delta drive starts at ₹8,180 (VFD007EL21W-1), a 5 HP three-phase drive at ₹19,900 (VFD9A0MS43ANSAA) and a 10 HP three-phase drive at ₹28,500 (VFD17AMS43ANSAA). The drive replaces the starter's contactor and overload relay because it has its own motor overload protection, but it still needs the input protection the manual specifies. See how to size a VFD and the VFD price list.

Which starter for a 10 HP motor?

For a 10 HP (7.5 kW) motor at 415 V: if the supply can take the inrush and the load is simple, DOL is fine; if the motor is a six-terminal delta motor driving a pump, fan or light-start compressor and you want lower starting current, use star-delta; if you need speed control or energy saving, use a VFD. Add single-phasing protection such as the Minilec VSP D1 (₹1,185) on three-phase pump motors. The free motor starter & VFD calculator suggests the contactor, overload relay, MPCB and VFD for your motor, and the overload relay sizing guide explains the settings. Browse contactors, star-delta timers and AC drives.

Why buy from Voltkart

• Genuine Delta drives and genuine Schneider contactors, overload relays and MPCBs from stock, with a GST invoice on every order.
• Authorised distributor of Selec and EAPL (star-delta timers) and Minilec (single-phase preventors).
• Pan-India dispatch; typically 2–3 days to Delhi NCR, UP and Haryana and 5–6 days elsewhere.
• Send the motor nameplate on WhatsApp +91 8800754881 (Mon–Sat, 12:30–7 pm) and we will suggest the starter or drive.

Frequently asked questions

Which is better, DOL or star-delta?

DOL gives full starting torque and is simpler and cheaper, but draws about 6 to 8 times full-load current. Star-delta cuts starting current and torque to about one-third, so it suits delta motors driving light-start loads such as pumps and fans.

What size contactors does a star-delta starter need?

The main and delta contactors carry about 58% of the motor full-load current and the star contactor about 33%. For a 10 HP motor with 15.5 A full-load current, 9 A contactors are typical.

Where is the overload relay set in a star-delta starter?

When the relay is in the main (winding) circuit, set it to about 58% of the motor full-load current, for example about 9 A for a 15.5 A motor.

Can any motor be started in star-delta?

No. The motor must be designed to run in delta at the supply voltage and have six terminals, for example a 415 V delta motor on a 415 V supply.

Is a VFD better than a star-delta starter?

A VFD gives a smoother start at lower current and adds speed control and energy saving, but costs more. For a fixed-speed delta motor that starts lightly, star-delta is the economical choice.