Fareed Mohmed · Engineering

Servo Motor Sizing Calculator

Reflect · Ratio · Torque · Real motors

Reflect a rotary or linear load’s inertia back to the motor shaft, check the inertia ratio, and calculate the peak and RMS torque a servo motor must deliver over a trapezoidal move. Then shortlist real Inovance, Omron, Delta and Misumi servo motors with the matching drive, each checked with its own rotor inertia, and check any other motor by hand.

This covers inertia matching and torque sizing for a single-axis point-to-point move, which is where most sizing mistakes come from. It does not replace the maker’s sizing software, which also checks the torque-speed curve, thermal duty over a full multi-move cycle, braking energy and resonance from mechanical compliance. Motor and drive data are Inovance, Omron, Delta and Misumi catalogue figures; other brands are not loaded yet.

Start Here: Sizing a Servo Axis

A servo motor is chosen by three limits, not one: how much inertia it has to control, how hard it has to push for a short time (peak torque) and how much heat the whole cycle makes (RMS torque). These six steps give the order. Read them once, then use sections 01 to 06.

Reflect the load to the motor shaft

Gearbox, screw or belt: bring the load inertia (or mass) back to the motor shaft so that it can be compared with a rotor.

Start in section 01 →

Describe the move

Target speed, accel and decel time, run time, dwell and the external load torque (friction, gravity, process).

Enter it in section 03 →

Let the tool shortlist real motors

Choose the brand and drive family, supply voltage and whether you need a brake. The tool adds each motor’s own rotor inertia, recalculates its torques and keeps those that pass six checks.

Find a motor in section 04 →

Look at the margins

The shortlist shows how much of the rating the move uses and the inertia ratio. Try a longer accel time or a gearbox if the best fit is too tight.

Match the drive

The peak torque needs the drive’s peak current. Check the drive ratings and, for fast stops or vertical loads, the braking resistor.

See the drives in section 06 →

Confirm before you order

Check the torque-speed curve in the maker’s guide and the maker’s sizing software. This page covers one axis and one move.

Common mistakes

Sizing on kilowattsRated power is torque times speed. A 0.4 kW motor can be too weak for a heavy low-speed axis and too big for a fast light one. Size on torque and inertia.

Leaving out the rotor inertiaThe motor has to accelerate its own rotor as well as the load. Torque needed rises with the motor chosen, so the tool recalculates it for each one.

Checking only peak torqueThe motor can pass on peak and still overheat. RMS torque over the whole cycle, including the dwell, must stay under the rated torque.

Forgetting the oil sealAn oil seal adds friction, so some makers derate the motor: Inovance by 10 % on its 60 mm and larger models, Omron by 5 to 20 % on three small 1S-with-safety motors. Ask the maker for your motor.

Peak torque at high speedPeak torque is not available all the way to maximum speed. Above the rated speed the usable torque falls, so read the torque-speed curve.

Z version or R versionThe same Inovance model name has different max speed and inertia in the older MS1-Z and the newer MS1-R data. Read the last letter of the order code.

Comparing across seriesOmron 1S, 1S with safety and G5 motors of the same power differ in rotor inertia, max speed and encoder. Do not swap one for another without redoing the check.

Using the brake to stopA holding brake keeps a stopped motor still. It is not for braking a moving load. Stop with the drive, then close the brake.

A drive too small for the peakPeak torque comes from peak current. A drive whose maximum current is below the motor’s gives less peak torque than the motor sheet prints.

Brands that make this product

Outlined gold: motor and drive data loaded from the maker’s catalogue (Inovance, Omron, Delta and Misumi). Grey dashed: not loaded yet. Confirm every model against the maker’s catalogue before you order.

INOVANCEInovancemotor and drive data

Omronmotor and drive data

Deltamotor and drive data

Misumimotor and drive data

Mitsubishi Electricnot yet

Yaskawanot yet

Siemensnot yet

Panasonicnot yet

See all hardware and brand coverage

Brand names and logos are trademarks of their owners and are shown only to identify catalogues.

Reflected Load Inertia

Reflects the load's inertia (or mass, for a linear axis) back to the motor shaft so it can be compared against the motor's own rotor inertia.

Load Type

Worked example for this load type

An indexing table is driven through a 10:1 gearbox. The table, its fixture and the parts on it add up to 300 kg·cm² at the table shaft (a steel disc of 200 mm diameter and 25 mm thickness is about 308 kg·cm²: try it in the box below). The motor sees it divided by 10², so the answer is 3.00 kg·cm². A gearbox cuts the load inertia by the ratio squared, which is why a small motor can drive a heavy table.

A roller is coupled straight to the motor shaft. Its inertia is 18 kg·cm², and with no gearbox the motor sees all of it. Use this mode for a motor-mounted flywheel, a direct-drive rotary table or a coupled shaft. If you add a coupling, put its inertia in the last box.

A carriage and workpiece weigh 40 kg on a ball screw with a 10 mm lead. The screw (about 25 mm × 500 mm, steel) plus coupling weigh in at roughly 1.5 kg·cm²: calculate the screw in the box below as a solid cylinder and put the result in the last box. The moving mass gives only about 1.0 kg·cm² at the motor (a long lead reflects very little), so the total is about 2.5 kg·cm²: here the screw matters more than the load. Take the mass and lead from your design and the catalogue; the lead is the travel per screw turn.

A carriage and load weigh 3 kg on a belt driven by a 40.7 mm pitch-diameter pulley (16 teeth, 8 mm pitch). The pulley is aluminium, about 0.3 kg·cm²: calculate it below and put it in the last box. The mass gives about 12.4 kg·cm², so the total is about 12.7 kg·cm². A belt reflects the mass at the pulley radius, so it is far heavier for the motor than a ball screw of the same mass. Heavy belt axes normally use a gearbox, which is not in this mode: work out the load inertia at the gearbox output and divide it by the ratio squared yourself. If you only know teeth and pitch, use the helper below: D = teeth × pitch ÷ π.

Load Inertia at the Load, J_L kg·cm²

Gear Reduction Ratio, N (motor : load) e.g. 5 = 5:1 reducer

Load Inertia, J_L kg·cm², already at motor speed

Moving Mass, m kg — carriage + workpiece

Screw Lead, L mm per revolution

Moving Mass, m kg — carriage + workpiece

Pulley Pitch Diameter, D mm

Coupling / Screw / Pulley Inertia (optional) kg·cm², reflected inertia of the coupling and any screw/pulley itself — leave 0 if unknown/negligible

Don’t know the inertia? Calculate it from the part

Pick the shape, enter the sizes in millimetres, and choose the material, or type the mass if you know it. Then send the result to the field above. Use Add to build up several parts one at a time (a disc, then a hub, then a fixture). The inertia must be taken about the axis the part turns on.

Shape

MaterialDensity. Ignored if you type a mass below.

Diameter, Dmm

Thickness or length, Lmm, along the axis

Outer diametermm

Inner diametermm

Lengthmm

Side amm

Side bmm, the two sides seen along the axis

Thicknessmm, along the axis

Axis offset from centremm, 0 if the axis passes through the centre

Distance from the axismm, to the centre of the mass

Masskg. Treated as a point, so it is slightly low for a bulky payload.

Known mass (optional)kg. If you type it, it replaces the mass worked out from size and material.

Mass—

Inertia about the axis—

Pulley teeth

Belt pitchmm (T10 = 10, HTD 5M = 5, 8M = 8)

Pitch diameter

—

Reflected Load Inertia, J_L'—

Gearbox: J_L' = J_L / N² + J_c. Ball screw: J_L' = m·(L / 2π)² + J_c (L converted to metres per revolution). Belt & pulley: J_L' = m·r² + J_c, r = pulley pitch radius. Carries down to section 02 automatically.

Inertia Ratio Check

Ratio = Reflected Load Inertia / Motor Rotor Inertia — a quick check on how well the motor and load are matched for dynamic response and tuning.

Reflected Load Inertia, J_L' kg·cm², auto-filled from section 01

Motor Rotor Inertia, J_M kg·cm², from the motor datasheet

Inertia Ratio, J_L' / J_M—

Assessment—

Where do I get J_M? From the motor’s datasheet, or let section 04 do it: pick a motor in the “Pick a motor” list there and this box fills with that motor’s own rotor inertia. If you have no motor yet, leave it as it is and use the section 04 shortlist, which tests each motor with its own inertia. As a rule of thumb, ratios up to 5 : 1 are comfortable for most axes. Many makers allow more, up to 10 : 1 or beyond for slow, smooth moves. Check the limit printed for the motor you buy.

Peak & RMS Torque — Trapezoidal Move

A standard accelerate / run / decelerate / dwell move cycle. T = J·α + T_load during acceleration and deceleration; only T_load applies at constant speed and during the dwell.

Total Inertia at Motor Shaft, J_total kg·cm² — J_L' + J_M, auto-filled

Target Speed, n RPM, at the motor

External Load Torque, T_load N·m at motor shaft — friction, gravity, process load

Accel Time, t_a s

Run Time, t_c s, at constant speed

Decel Time, t_d s

Dwell Time, t_dw s, stopped between moves

Don’t know the speed or the load torque? Work them out

These helpers use the load type, lead and pulley size you set in section 01, so fill that section first.

Motor speed from the speed of the load

Load speedmm/s

Motor speed

—

Load torque at the motor shaft

Moving masskg, carriage plus workpiece

Friction coefficientabout 0.01 to 0.02 for linear guides, 0.1 to 0.2 for sliding ways (assumed values, confirm for yours)

Slope angledegrees: 0 flat, 90 vertical lift

Process forceN, e.g. a cutting, pressing or pushing force

Torque needed at the load shaftN·m, friction plus process torque at the load

Efficiency of the drive%. About 90 for a ball screw, 95 for a belt, 85 to 95 for a gearbox (typical, confirm for yours)

Load torque, T_load

—

Choosing the times

The four times come from your machine’s required cycle. For a move of distance s that must finish in time t, with equal acceleration and deceleration times, the run time is t_c = s ÷ v − t_a, where v is the top speed. A shorter t_a means a higher peak torque, because the acceleration torque is inversely proportional to it. Start with an acceleration time of about a fifth to a third of the move time, then see how the peak and RMS torques change. Dwell is the stopped time before the next move, and it lowers the RMS torque, so enter the true figure.

Accel-Phase Torque—

Run-Phase Torque—

Decel-Phase Torque—

Peak Torque Required—

RMS Torque Required—

Cycle Time—

A negative decel-phase torque means the load is decelerating faster than the external load alone would slow it — the motor is absorbing (regenerating) energy rather than driving. RMS torque assumes this one move repeats back-to-back; for a mixed cycle of different moves, extend the same sum-of-(T²·t) / total-time formula across all of them.

Find a Motor from Supplier Data

Shortlists real motors from the Inovance, Omron, Delta and Misumi catalogues. For each motor the tool adds its rotor inertia to the load inertia from section 01, recalculates peak and RMS torque for your move in section 03, and checks voltage, brake, speed, peak torque, RMS torque and inertia ratio. Passing motors are listed smallest first.

Brand and drive familyEach family has its own motors and limits, so choose the drive you will buy

SupplyVoltage class of the motor and drive

Holding brakeNeeded for vertical axes and for holding on power loss

Inertia ratio limitLoad : rotor

Torque marginAdded to the peak and RMS torque you need

Oil-seal deratingAssumes an oil seal is fitted. Used only where the maker prints a derating (Inovance 10 %, three Omron 1SA motors)

Check Against a Candidate Motor

Pick a motor from the supplier data (optional)Fills the two torque boxes here and the rotor inertia in section 02. The list follows the drive family you chose in section 04.

Candidate Motor — Continuous Rated Torque N·m, from the datasheet

Candidate Motor — Peak (Instantaneous Max) Torque N·m, from the datasheet

RMS vs. Continuous Rating—

Peak vs. Peak Rating—

Passing both checks with zero margin is not a safety margin — see the notes below on why headroom matters before finalizing a motor.

Drives and Braking Resistors

Inovance first, then Omron. The three Inovance SV660 drive families use the same power stage. Only the command interface differs, so the ratings below are the same for N, P and F. The model name is SV660 + N, P or F + the code + I, for example SV660NS012I.

Inovance drive ratings

Drive	Frame	Power	Supply	Rated A	Max A	Built-in braking resistor	Min. external resistor
S1R6	A	0.2 kW	Single-phase 220 V	1.6	5.8	None built in	40 Ω
S2R8	A	0.4 kW	Single-phase 220 V	2.8	10.1	None built in	45 Ω
S5R5	B	0.75 kW	Single-phase 220 V	5.5	16.9	50 Ω, 50 W	40 Ω
S7R6	C	1 kW	Single or three-phase 220 V	7.6	23	25 Ω, 80 W	20 Ω
S012	D	1.5 kW	Single or three-phase 220 V	11.6	32	25 Ω, 80 W	15 Ω
T3R5	C	1 kW	Three-phase 380 to 440 V	3.5	11	100 Ω, 80 W	80 Ω
T5R4	C	1.5 kW	Three-phase 380 to 440 V	5.4	14	100 Ω, 80 W	60 Ω
T8R4	D	2 kW	Three-phase 380 to 440 V	8.4	20	50 Ω, 80 W	45 Ω
T012	D	3 kW	Three-phase 380 to 440 V	11.9	29.75	50 Ω, 80 W	40 Ω
T017	E	5 kW	Three-phase 380 to 440 V	16.5	41.25	35 Ω, 100 W	35 Ω
T021	E	6 kW	Three-phase 380 to 440 V	20.8	52.12	35 Ω, 100 W	25 Ω
T026	E	7.5 kW	Three-phase 380 to 440 V	25.7	64.25	35 Ω, 100 W	25 Ω

The built-in resistor is the one fitted as standard. The two smallest drives have none, so use an external resistor. An external resistor must not be below the minimum value. Choose its power from the real braking duty, not from the table.

The three drive families

	SV660N	SV660P	SV660F
Command interface	EtherCAT (CiA 402)	Pulse and analog, Modbus RS485 (CANopen and CANlink variants are also offered)	Profinet RT and IRT
Control modes	Position (CSP, PP, homing), speed (CSV, PV), torque (CST, PT)	Position by pulse (up to 4 Mpps differential), speed, torque, 16 internal positions	Position, speed and torque over Profinet
Digital I/O	5 inputs, 2 outputs	7 inputs, 5 outputs	See the SV660F guide
Motors in the guide	MS1-R	MS1 (R and Z)	MS1 (R and Z)
Power range	0.05 to 7.5 kW	0.05 to 7.5 kW	0.05 to 7.5 kW

All three have a 23-bit multi-turn absolute encoder input (a battery keeps the position when power is off), a 1 : 6000 speed range, inertia auto-tuning and five notch filters. Safe torque off (STO) is listed for SV660N in its guide; check the guide of the drive you order for the safety options.

Omron drives paired with the loaded motors

Family	Drive	Supply	Rated A	Max A	Motors paired in the catalogue
1S	R88D-1SN01H-ECT	Single or three-phase 200 to 240 V	0.8	3.1	0.05 to 0.1 kW
1S	R88D-1SN02H-ECT	Single or three-phase 200 to 240 V	1.5	5.6	0.2 kW
1S	R88D-1SN04H-ECT	Single or three-phase 200 to 240 V	2.5	9.1	0.4 kW
1S	R88D-1SN08H-ECT	Single or three-phase 200 to 240 V	4.6	16.9	0.75 kW
1S	R88D-1SN15H-ECT	Single or three-phase 200 to 240 V	9.7	28.4	0.9 to 1.5 kW
1S	R88D-1SN06F-ECT	Three-phase 380 to 480 V	1.8	5.5	0.4 to 0.6 kW
1S	R88D-1SN10F-ECT	Three-phase 380 to 480 V	4.1	9.6	0.75 to 1 kW
1S	R88D-1SN15F-ECT	Three-phase 380 to 480 V	4.7	14.1	1.5 kW
1S	R88D-1SN20F-ECT	Three-phase 380 to 480 V	7.8	19.8	2 kW
1S	R88D-1SN30F-ECT	Three-phase 380 to 480 V	11.3	28.3	3 kW
1S	R88D-1SN55F-ECT	Three-phase 380 to 480 V	14.5	42.4	4 to 5.5 kW
1S	R88D-1SN75F-ECT	Three-phase 380 to 480 V	22.6	56.5	7.5 kW
1S	R88D-1SN150F-ECT	Three-phase 380 to 480 V	33.9	84.8	11 to 15 kW
1S with safety	R88D-1SAN02H-ECT	Single or three-phase 200 to 240 V	1.5	5.6	0.2 kW
1S with safety	R88D-1SAN04H-ECT	Single or three-phase 200 to 240 V	2.5	9.1	0.4 kW
1S with safety	R88D-1SAN08H-ECT	Single or three-phase 200 to 240 V	4.6	16.9	0.75 kW
1S with safety	R88D-1SAN10H-ECT	Three-phase 200 to 240 V	7.7	16.9	1 kW
1S with safety	R88D-1SAN15H-ECT	Single or three-phase 200 to 240 V	9.7	28.4	1.5 kW
1S with safety	R88D-1SAN20H-ECT	Three-phase 200 to 240 V	16.2	41	2 kW
1S with safety	R88D-1SAN30H-ECT	Three-phase 200 to 240 V	22.3	54.7	2.6 to 2.7 kW
1S with safety	R88D-1SAN10F-ECT	Three-phase 380 to 480 V	4.1	9.6	0.75 to 1 kW
1S with safety	R88D-1SAN15F-ECT	Three-phase 380 to 480 V	4.7	14.1	1.5 kW
1S with safety	R88D-1SAN20F-ECT	Three-phase 380 to 480 V	7.8	19.8	2 kW
1S with safety	R88D-1SAN30F-ECT	Three-phase 380 to 480 V	11.3	28.3	3 kW
G5	R88D-KTA5L / KNA5L-ECT	Single-phase 100 to 120 V	1.2	not in the loaded pages	0.05 kW
G5	R88D-KT01L / KN01L-ECT	Single-phase 100 to 120 V	1.7	not in the loaded pages	0.1 kW
G5	R88D-KT02L / KN02L-ECT	Single-phase 100 to 120 V	2.5	not in the loaded pages	0.2 kW
G5	R88D-KT04L / KN04L-ECT	Single-phase 100 to 120 V	4.6	not in the loaded pages	0.4 kW
G5	R88D-KT01H / KN01H-ECT	Single or three-phase 200 to 240 V	1.2	not in the loaded pages	0.05 to 0.1 kW
G5	R88D-KT02H / KN02H-ECT	Single or three-phase 200 to 240 V	1.6	not in the loaded pages	0.2 kW
G5	R88D-KT04H / KN04H-ECT	Single or three-phase 200 to 240 V	2.6	not in the loaded pages	0.4 kW
G5	R88D-KT08H / KN08H-ECT	Single or three-phase 200 to 240 V	4.1	not in the loaded pages	0.75 kW
G5	R88D-KT10H / KN10H-ECT	Single or three-phase 200 to 240 V	5.9	not in the loaded pages	1 kW
G5	R88D-KT15H / KN15H-ECT	Single or three-phase 200 to 240 V	9.4	not in the loaded pages	0.9 to 1.5 kW
G5	R88D-KT20H / KN20H-ECT	Three-phase 200 to 230 V	13.4	not in the loaded pages	2 kW
G5	R88D-KT30H / KN30H-ECT	Three-phase 200 to 230 V	18.7	not in the loaded pages	2 to 3 kW
G5	R88D-KT50H / KN50H-ECT	Three-phase 200 to 230 V	33	not in the loaded pages	3 to 5 kW
G5	R88D-KT75H / KN75H-ECT	Three-phase 200 to 230 V	44	not in the loaded pages	6 to 7.5 kW
G5	R88D-KT150H / KN150H-ECT	Three-phase 200 to 230 V	66.1	not in the loaded pages	11 to 15 kW
G5	R88D-KT06F / KN06F-ECT	Three-phase 380 to 480 V	1.5	not in the loaded pages	0.4 to 0.6 kW
G5	R88D-KT10F / KN10F-ECT	Three-phase 380 to 480 V	2.9	not in the loaded pages	0.75 to 1 kW
G5	R88D-KT15F / KN15F-ECT	Three-phase 380 to 480 V	4.7	not in the loaded pages	0.9 to 1.5 kW
G5	R88D-KT20F / KN20F-ECT	Three-phase 380 to 480 V	6.7	not in the loaded pages	2 kW
G5	R88D-KT30F / KN30F-ECT	Three-phase 380 to 480 V	9.4	not in the loaded pages	2 to 3 kW
G5	R88D-KT50F / KN50F-ECT	Three-phase 380 to 480 V	16.5	not in the loaded pages	3 to 5 kW
G5	R88D-KT75F / KN75F-ECT	Three-phase 380 to 480 V	22	not in the loaded pages	6 to 7.5 kW
G5	R88D-KT150F / KN150F-ECT	Three-phase 380 to 480 V	33.4	not in the loaded pages	11 to 15 kW

Delta drives paired with the loaded motors

Family	Drive	Supply	Rated A	Max A	Motors paired by the tool
ASDA-B3	ASD-B3-0121-x	Single or three-phase 200 to 230 V	0.9	3.88	0.05 to 0.1 kW
ASDA-B3	ASD-B3-0221-x	Single or three-phase 200 to 230 V	1.55	7.07	0.2 kW
ASDA-B3	ASD-B3-0421-x	Single or three-phase 200 to 230 V	2.65	10.6	0.4 kW
ASDA-B3	ASD-B3-0721-x	Single or three-phase 200 to 230 V	5.1	16.4	0.75 kW
ASDA-B3	ASD-B3-1021-x	Single or three-phase 200 to 230 V	7.3	21.21	1 kW
ASDA-B3	ASD-B3-1521-x	Three-phase 200 to 230 V	8.3	27	1.5 kW
ASDA-B3	ASD-B3-2023-x	Three-phase 200 to 230 V	13.4	38.3	2 kW
ASDA-B3	ASD-B3-3023-x	Three-phase 200 to 230 V	19.4	58.9	3 kW
ASDA-A3-EP	ASD-A3x-0443-EP	Three-phase 380 to 480 V	1.6	5.4	0.4 kW
ASDA-A3-EP	ASD-A3x-0743-EP	Three-phase 380 to 480 V	3.12	9.7	0.75 to 1 kW
ASDA-A3-EP	ASD-A3x-1043-EP	Three-phase 380 to 480 V	3.52	10.54	0.85 to 1 kW
ASDA-A3-EP	ASD-A3x-1543-EP	Three-phase 380 to 480 V	5.06	16.35	1.3 to 2 kW
ASDA-A3-EP	ASD-A3x-2043-EP	Three-phase 380 to 480 V	6.6	19.88	1.8 to 2 kW
ASDA-A3-EP	ASD-A3x-3043-EP	Three-phase 380 to 480 V	9.11	29.45	3 kW
ASDA-A3-EP	ASD-A3x-4543-EP	Three-phase 380 to 480 V	13.3	35.35	4.5 kW
ASDA-A3-EP	ASD-A3x-5543-EP	Three-phase 380 to 480 V	15.34	49.29	5.5 kW
ASDA-A3-EP	ASD-A3x-7543-EP	Three-phase 380 to 480 V	22.4	56.68	7.5 kW
ASDA-A3-EP	ASD-A3x-1B43-EP	Three-phase 380 to 480 V	27.3	68.25	11 kW
ASDA-A3-EP	ASD-A3x-1F43-EP	Three-phase 380 to 480 V	31	80.2	15 kW

Misumi drives paired with the loaded motors

Motor series	Drive	Supply	Rated A	Max A	Motors paired
E-MASH1 (economy)	E-DFAS01P / E-DFAS01E	Single-phase 200 to 240 V	1.2	3.4	0.1 kW
E-MASH1 (economy)	E-DFAS04P / E-DFAS04E	Single-phase 200 to 240 V	3.5	9.5	0.2 to 0.4 kW
E-MASH1 (economy)	E-DFAS08P / E-DFAS08E	Single-phase 200 to 240 V	5.5	16.6	0.75 kW
E-MASH1 (economy)	E-DFAS10P / E-DFAS10E	Single-phase 200 to 240 V	7	21	1 kW
E-MASH2 (full function)	E-DHAS01P-F / E-DHAS01E-F	Single or three-phase 200 to 240 V	1.2	4.8	0.1 kW
E-MASH2 (full function)	E-DHAS04P-F / E-DHAS04E-F	Single or three-phase 200 to 240 V	2.8	9.3	0.2 to 0.4 kW
E-MASH2 (full function)	E-DHAS08P-F / E-DHAS08E-F	Single or three-phase 200 to 240 V	5.5	16.9	0.75 kW
E-MASH2 (full function)	E-DHAS10P-F / E-DHAS10E-F	Single or three-phase 200 to 240 V	7	21	1 kW
E-MASS2 (full function)	E-DHAS01P-F / E-DHAS01E-F	Single or three-phase 200 to 240 V	1.2	4.8	0.1 kW
E-MASS2 (full function)	E-DHAS04P-F / E-DHAS04E-F	Single or three-phase 200 to 240 V	2.8	9.3	0.2 to 0.4 kW
E-MASS2 (full function)	E-DHAS08P-F / E-DHAS08E-F	Single or three-phase 200 to 240 V	5.5	16.9	0.75 kW
E-MASS2 (full function)	E-DHAS10P-F / E-DHAS10E-F	Single or three-phase 200 to 240 V	7	21	1 kW

The P and E in a Misumi drive name are the pulse (with RS485) and EtherCAT versions. The two versions have the same rated current. Where their maximum current differs (E-DFAS), the table and the tool show the lower figure. The 200 W motors are paired with the 400 W drive, as Misumi prints. E-DFAS is the economy range and E-DHAS the full-function range. Braking resistors for the Misumi drives are not loaded.

Delta’s catalogue lists the 400 V drive for each motor, and the tool uses it. For the 200 V motors the tool pairs the drive of the same power rating (for example 0.4 kW with the 400 W drive), which is the usual match; check the maker’s combination table before ordering. The last letter of an ASD-B3 name stands for the interface: L pulse, M CANopen, F DMCNET, E EtherCAT. The “x” in ASD-A3x stands for the same choice. Braking resistors for the Delta drives are not loaded.

Each motor in section 04 is shown with the drive Omron pairs it with in its catalogue. Some pairings are marked by Omron as a larger or smaller drive than the motor’s power (for example G5 50 W, 1 kW, 4 kW and 11 kW, and all G5 1,000 rpm motors), so use the pairing as printed. The G5 pages loaded give the drive’s continuous current only, so the maximum current shows as not loaded. 1S is the EtherCAT series with a 23-bit encoder. 1S with safety adds the STO, SS1, SS2, SOS, SLS, SLP, SDI and SBC functions (SIL 3, PL e) and has a 20-bit encoder. G5 comes as the KT (pulse or analog) and KN (EtherCAT or MECHATROLINK-II) drives, which share one power stage. Braking resistors for the Omron drives are not loaded.

Reference Tables

Inertia Ratio (Load : Rotor)	Typical Assessment
≤ 1 : 1	Excellent — highest achievable dynamic response and tuning stability
1 : 1 – 5 : 1	Good — the comfortable range for most general machine building
5 : 1 – 10 : 1	Acceptable — tunable on most modern drives, verify with autotune
> 10 : 1	High — increase the gear reduction, add a gearbox, or step up motor frame size

A widely used rule-of-thumb across servo drive manufacturers, not a hard physical limit — some modern drives with advanced tuning tolerate ratios well past 10:1. Always confirm against your specific drive's tuning guide.

Load Type	Reflected Inertia Formula
Rotary, through a gearbox	J_L' = J_L / N²
Rotary, direct-coupled	J_L' = J_L
Linear, ball screw	J_L' = m · (L / 2π)² (L = lead, m/rev)
Linear, belt & pulley	J_L' = m · r² (r = pulley pitch radius)

Explanatory Notes

How the motor shortlist works

For each motor the tool takes your reflected load inertia and adds that motor’s rotor inertia (the braked figure if you need a brake). It then recalculates the acceleration torque, T = J_total × α + T_load, with the speed and times from section 03, and gets the peak and the RMS torque over the whole cycle including the dwell. A motor passes if the peak (plus margin) is under its maximum torque, the RMS (plus margin) is under its rated torque, the speed is under its maximum speed, the inertia ratio is under your limit, and the voltage and brake choices match.

Two guides, two sets of limits

The SV660N guide documents the newer MS1-R motors. The SV660P and SV660F guides (identical for motors) document MS1 motors whose maximum speed and torque are lower for some sizes, for example 3,000 rpm instead of 4,500 rpm for the 130 and 180 mm medium-inertia motors. The maker states that the maximum speed and torque of a motor vary slightly with the drive series. So the tool keeps the two sets apart: choose the family of the drive you will buy. The 40 mm models in the P and F guides are the older Z version.

What the tool leaves out

The printed torque-speed curves (the continuous and intermittent zones, and the heatsink derating curve) are not loaded. The tool checks rated and peak torque, and warns when your speed is above the rated speed. It does not apply ambient or altitude derating: the maker derates above 40 °C ambient and above 1,000 m. It does not check the drive’s maximum output current against the motor except as printed, braking energy or the regeneration limit. The MS1 motors with flying leads (“-S”) and the T-series variants are not listed separately.

Catalogue points to know

In the SV660N guide, MS1H2-20C30CB is printed with 19.1 N·m peak at 42 A, but the drive it is paired with (S012) has 32 A maximum. The P and F guides print 15.5 N·m for the same motor, and the tool uses 15.5. For a few other motors the motor’s maximum current is within about 4 % above the drive’s, which the tool ignores. Four 220 V motors of 2.5 to 5 kW and two 220 V MS1H3 motors appear in the data pages of the P and F guides, but have no drive in that guide’s selection table, so they are not loaded.

Omron: three series, three sets of limits

Omron’s 1S (R88M-1), 1S with safety (R88M-1A) and G5 (R88M-K) are kept apart because the same power does not mean the same motor. For example the 750 W, 3,000 rpm motors have rotor inertias of 1.82, 1.83 and 0.87 kg·cm² in 1S, 1S with safety and G5. Pick the series of the drive you will buy. Each motor is listed with the 24 V holding brake version and the key-and-tap shaft (S2). The order code shows the absolute-encoder, no-oil-seal model; Omron also sells incremental-encoder versions and an oil-seal version of each.

Omron: what to know about the data

The 1S motor datasheet prints no oil-seal derating, so none is applied to 1S or G5. The 1S with safety guide prints 95 %, 80 % and 90 % for the 200, 400 and 750 W motors with an oil seal, and the tool applies those. The G5 maximum speed and the 2,000 and 1,500 rpm groups were read from grouped table cells, so confirm the maximum speed of a 4 kW and larger G5 motor in the maker’s sheet. G5 15 kW prints 95.0 N·m for 200 V and 95.9 N·m for 400 V (the physical value is 95.5). Omron also prints a maximum applicable load inertia: 10 to 30 times the rotor inertia for G5, and about 10 to 22 times for the 1S with safety 200 to 750 W motors. Keep the ratio limit you choose below the maker’s. G5 flange sizes are shown for the 3,000 rpm motors only, because the other flange sizes are not in the pages loaded.

Delta: what to know about the data

The Delta B3 catalogue covers the ECM-B3 and ECM-A3 200 V motors; the ASDA-A3-EP catalogue covers the ECM-B3 400 V motors. The ASDA-A3-EP manual has no motor tables and was not used for motor data. The order code shown is a typical build (absolute encoder, keyway with oil seal, standard connector); Delta also sells other encoder, shaft and connector variants, so confirm the letters on the maker’s ordering page. The oil-seal derating is applied as printed in the rated-torque footnotes. The 400 V tables do not print the brake rotor inertia, so it is taken from the combination table, and the weight with brake for 400 V motors is not loaded. The rated and maximum speeds of four 200 V motors (ECM-B3M-C0807 and E1310, E1315, E1320) were read by hand because the table cells were merged. Motors with a 100 V supply are not loaded.

Misumi: what to know about the data

Misumi sells its own E-MASH1, E-MASH2 and E-MASS2 motors in five sizes (100 W to 1 kW, 220 V, 3,000 rpm rated). The E-MASH1 maximum speed is 6,000 rpm and the E-MASH2 and E-MASS2 figure is 6,500 rpm. The E-MASS2 has about half the rotor inertia of the E-MASH2 at the same torque, so it suits fast, light axes better. The catalogue does not print the brake holding torque, so the tool leaves it out and shows only that a brake version exists (order code with B). It also prints no oil-seal derating. The catalogue lists Mitsubishi, Panasonic and Yaskawa motors as options for Misumi actuators, but gives only model names and power for them, so they are not loaded here. They will come with those makers’ own catalogues. The E-MASH1 1 kW peak torque is printed as 11.4 N·m, against 11.14 N·m for the same-size E-MASH2, and the tool uses the printed figure for each.

Not loaded

The older Inovance ISMH motors with IS620 drives (same ratings as the MS1-Z), the ISMG servo-pump motors, the Omron 1S motors on 100 V drives, the G5 flat-type, linear and decelerator combinations, and the other brands in the strip above (Mitsubishi, Yaskawa, Siemens, Panasonic). They will be added as their catalogues are provided.

Why the inertia ratio matters before torque even enters the picture

A servo drive's tuning loop is trying to control the combined motor-plus-load inertia through the motor's own encoder — the load's inertia is invisible to the drive except through how the whole system responds. A high inertia ratio means the "tail wags the dog": the load dominates the system's dynamics, making it easy to excite mechanical resonance and hard to tune for both stiffness and stability. Fixing this after the fact (by re-gearing or changing motor frame size) is far more disruptive than sizing it right the first time.

RMS torque, not peak torque, sizes the motor's continuous rating

A motor's continuous torque rating is a thermal limit — how much heat its windings can shed indefinitely without overheating. Peak torque is only needed for the short acceleration bursts; if the RMS torque exceeds the continuous rating, the motor cooks even though it may never see the peak torque limit at any single instant. Both numbers matter, and they're sized against different limits in the datasheet.

Zero margin is not a design point

A candidate motor that just barely passes both checks above leaves nothing for an underestimated friction coefficient, a heavier-than-spec workpiece, a faster future cycle time, or winding resistance rising with temperature. A common practice is to keep continuous torque demand under roughly 70–80% of the motor's rated continuous torque, leaving headroom for exactly this kind of real-world variance — confirm the margin convention your own organization uses.

Related tools

For the shaft or coupling carrying this load, see the Shaft Design Calculator and Coupling Selection Calculator. For gear-driven axes more broadly, see the Motor & Gearbox Selector and Motor & Gearbox Output Calculator.

Sources

All motor and drive figures were read from these Inovance, Omron, Delta and Misumi documents in October 2026. They are the maker’s figures at an armature temperature of 20 °C with the maker’s heatsink, so confirm the order code and the current revision with Inovance before you order.

Motors

SV660N Series Servo Drive Selection Guide, EN-C01 (MS1-R motor data, selection table, drive ratings). SV660P Series Servo Drive Selection Guide, EN-C00, and SV660F Series Servo Drive Selection Guide, EN-A02 (MS1 motor data for the P and F drives). The MS1 series motor brochure (V0.0) and the IS620 brochure (V4.1) show the older MS1-Z data and were used only to cross-check.

Drives

The same three guides for the drive ratings, braking resistors and specifications, with the SV660 series brochure and the SV660P product overview for the family description. The IS620N and ISMH user guide (A04) covers the older IS620 drives and ISMH motors and is not loaded.

Omron motors

R88M-1 1S Series servo motor datasheet (I189E) for the 1S motor ratings, selection tables and drive pairings. AC Servo System 1S-series with Safety Functionality, R88M-1A / R88D-1SAN-ECT (I842) for the 1S with safety motors and drives. R88M-K, R88D-KT, R88D-KN catalogue pages (I816) for the G5 motor ratings and drive currents, and the G5 Series catalogue (I815) for the combination tables.

Delta

ASDA-B3 catalogue (document dated 2021-10-01) for the 200 V ECM-B3 and ECM-A3 motor ratings and ASD-B3 / ASD-A3 drive ratings. ASDA-A3-EP catalogue for the 400 V ECM-B3 motor ratings, combination table and ASD-A3-EP drive ratings. ASDA-A3-EP manual: checked, no motor data used.

Misumi

Misumi catalogue, section 06 (Stepper Motors and Servo Motors): E-MASH1 motor specifications (page 06-017), E-MASH2 and E-MASS2 motor specifications (page 06-021), and the E-DFAS and E-DHAS drive specifications (pages 06-018 to 06-024).

Omron drives

AC Servo System 1S-series catalogue (I821) for the R88D-1SN drive ratings. The 1S, 1S with safety and 1S-51 (SS1/SLS) brochures were used to cross-check the safety functions and the product range.