Motor starter

01

Size the starter to the motor, the duty and the starting method

ABB's motor protection and control catalogue lists starter solutions for direct-on-line, reversing and star-delta starting, built from contactors, thermal or electronic overload relays and manual motor starters. It notes that its MS116, MS132, MO132, MS165 and MO165 manual motor starters suit IE3 and IE4 motors of design N/H and NE/HE, and that NE/HE motors require utilization category AC-3e. Citing IEC 60034-12, it defines designs NE and HE as having higher locked-rotor current than designs N and H. [1]

Its MS132 range gives thermal and electromagnetic protection from 0.10 to 32 A, up to 15 kW at 400 V, in a 45 mm width, with a built-in disconnect function, temperature compensation, trip-free mechanism and lockable rotary handle. The ordering table runs from 0.03 kW (0.10–0.16 A) to 11 kW (20–25 A) and beyond, with short-circuit breaking capacity Ics of 100 kA at 400 V up to the 20 A size and 50 kA at 25 A. The technical data list rated voltage 690 V AC, trip class 10 (10A for MS116), mechanical durability of 100,000 cycles and electrical durability of 50,000–100,000 cycles depending on current. [1]

For small motors with high switching rates, the catalogue lists an electronic compact starter that combines direct-on-line, reversing, overload protection and emergency stop in a 22.5 mm wide device, rated for 30 million switching cycles for motors up to 3 kW at 400 V. [1]

Editorial calculation: in ABB's MS132 table a 4 kW, 400 V motor maps to the 6.3–10 A size and a 7.5 kW motor to the 10–16 A size; the setting is then made to the motor's nameplate full-load current, not to the kW figure. [1]

Give the supplier the motor power, voltage, frequency, nameplate full-load current, efficiency class and design (N/H or NE/HE), starting method (DOL, reversing, star-delta), starts per hour, overload trip class, prospective short-circuit current at the starter, protective device and required coordination type, control voltage, enclosure and IP rating, ambient temperature, standards and approvals, and quantity.

02

Set the short-circuit protection and coordination type

ABB's catalogue states that IEC/EN 60947-4-1 and UL 60947-4-1 define two types of coordination between the branch-circuit protective device and the motor starter. Under Type 1, in short-circuit conditions the contactor or starter does not endanger persons or installations but cannot operate again without repair or replacement of parts. Under Type 2 it does not endanger persons or installations and can operate afterwards; light welding of contacts is acceptable, and the maker must state the maintenance measures. [1]

The same section says complete coordination covers a selectivity test between the overload relay and the short-circuit protective device and short-circuit tests at a prospective current r that depends on the starter's AC-3/AC-3e rated current — for example 1 kA up to 16 A, 3 kA from 16 to 63 A and 5 kA from 63 to 125 A — and at the rated conditional short-circuit current Iq, for example 50 kA. [1]

For North American panels, the catalogue notes that NEC Article 409 requires industrial control panels to be marked with a short-circuit current rating, with UL 508A Supplement SB as an accepted method, and lists combination motor controller constructions: Type A fusible, Type C inverse-time breaker, Type D instantaneous-only breaker, Type E self-protected and Type F (manual motor starter plus contactor). [1]

Editorial note: a starter's own breaking capacity is not the coordination rating; ask for the tested combination (protective device, contactor and overload relay) with its coordination type and Iq at your voltage.

03

Compare what suppliers offer

Suppliers linked to this page list motor starters; each card links to the page reviewed.

The listings reviewed include contactor-based magnetic starters rated up to 690 V AC with AC-3 duty, an integrated star-delta starter, magnetic starters for circuits up to 550 V, and motor-protection circuit breakers rated 690 V up to 63 A. Ask each for the coordination tables, trip class and approvals of the exact combination quoted. [2] [4] [6] [3] [5] [7]

04

Trace what each part of the starter does

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your motor

A motor starter quotation needs values for your motor and supply. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the motor, supply and protection data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Motor: [kW; V; Hz; FLC; IE class; design N/H/NE/HE]
Starting: [DOL; reversing; star-delta; starts/hour]
Overload: [trip class; thermal or electronic]
Short circuit: [prospective kA; fuse or breaker; Type 1 or 2]
Control: [coil voltage AC/DC]
Enclosure: [IP; mounting]
Approvals: [IEC; UL; other]
Quantity: [units]

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