The most common problem in electric motor orders is motors whose power and speed were stated correctly but whose frame size was never discussed, and which then do not seat in place when they reach the facility. The shaft height differs, the foot holes are shifted, the shaft diameter does not match the coupling; the motor is right, the machine is right, but the match is wrong. As a manufacturer, in our cast iron motor sales we make sure the frame number is written on the order form together with the power and speed, because this single line of information prevents return shipments and lost production days from the start. In this guide we explain the relationship between frame size and power from a purchasing perspective, gathering everything you need to select the right motor from stock the first time onto a single page.

As HEM Motor, we manufacture our cast iron framed motors from frame 63 up to frame 355L, in all standard sizes including 315HT. The information below comes directly from our own production and stock practice; speaking in these terms when you ask for a quote visibly speeds up the process.

What Is the Frame Number (Frame Size), and Where Is It on the Nameplate?

According to the IEC standard, the frame number is the value, in millimetres, of the height from the motor's foot mounting surface to the centre of the shaft axis. In a frame 90 motor the shaft axis is 90 mm above the floor, in frame 160 it is 160 mm, and in frame 355 it is 355 mm. The letters S, M, L next to the number indicate the short, medium or long package length of the frame at the same shaft height; for example, in 132S and 132M motors the shaft height is the same, but the distance between the foot holes differs.

This value appears within the type code on the motor nameplate. If you see an expression such as 112M, 160L, 250M, 315HT or 355L in the type text on the nameplate, that is your frame number. Adding this code to your quote request in a like-for-like replacement is the shortest way to guarantee that the motor you receive seats onto the existing base, coupling and pulley without any modification.

Frame number and shaft axis height measurement on a cast iron electric motor

Power, Speed and Frame Size Are Determined Together

Frame size depends not on power alone; power and speed determine the frame together. The rule is simple: at the same power, as the speed drops the torque the motor produces rises, so the frame grows. A 1000 rpm motor of the same kW value as one running at 1500 rpm is usually wound on a frame one size larger. That is why there is no single answer to the question "what frame is a motor of so many kW"; the correct form of the question is "what frame does this kW, at this speed, correspond to".

On the manufacturer side, this matching is managed with standard tables, and our stocks are also arranged according to those tables. In practice, the table you need to remember is not the chart but this trio: power (kW) + speed (rpm) + frame number. When you give this trio, our quote firms up within minutes; if one of the three is missing, our sales team has to ask anyway.

Large Power Example: Frame 355 and a Diameter 100 mm Shaft

The most concrete example of the power-frame relationship is the top end of the series: at 315 kW and 355 kW, at 1500 rpm, the common application in the Turkiye market is frame 355 with a diameter 100 mm shaft. An industrial electric motor of this class reaches several tons in weight; its coupling, pulley and base connection are also machined to this shaft diameter. At large powers, an order placed without frame and shaft information also leaves crane and installation planning uncertain. We also recommend you look at our high power motor supply guide, where we explain in detail the lead time, transport and commissioning plan of purchases above 90 kW.

Frame Ranges by Mounting Type

The frame number also determines which mounting types the motor can be manufactured in. The ranges in our own production program are as follows:

  • B3 (foot-mounted): Frame 63 - 355L, including 315HT. Connected by its feet to a chassis, platform or motor base; the standard for belt-pulley and coupled drives.
  • B5 (large flange, footless): Frame 63 - 355L. Bolted to a pump, gearbox or fan body via the front flange.
  • B14 (small flange, footless): Frame 56 - 160L. Due to the small flange structure, it is manufactured only in the lower and medium sizes; there is no B14 option above 160L.
  • B35 (foot + large flange): Frame 63 - 355L, including 315HT. For applications wanting both chassis and flange connection.
  • B34 (foot + small flange): Frame 63 - 160L.

As you can see, you cannot request a B14 flange on a motor of frame 200 and above; we catch such incompatibilities at the quote stage and offer you the correct alternative. If you are undecided about flange type, our B5 or B14 selection guide covers the subject in detail for machine builders. If you are looking for a foot-mounted motor, you can find all frame options from 63 to 355L on our B3 mounted electric motors page.

The Technical Framework of Our Cast Iron Frame Series

Talking about frame size cannot be separated from the frame material. Our cast iron framed electric motors are manufactured in the 0.55 kW - 355 kW power range, with 1000 / 1500 / 3000 rpm speed options, and in the IE3 Premium and IE4 Super Premium efficiency classes. IP55 protection class, F insulation class and 100% copper winding are standard across the series. The cast iron frame is especially important in large frame sizes: as the motor grows heavier, the mechanical load and vibration the frame carries increase, and the rigidity of the cast frame directly extends bearing life.

When buying an asynchronous motor, we recommend you also clarify the efficiency class in the same discussion; the IE3 and IE4 options on the same frame are kept together in our stocks. You can examine all of the high-efficiency series in our efficient electric motors category.

Cast iron electric motors of different frame sizes on a stock shelf

The Practical Field Equivalents of Frame Groups

When planning a purchase, you can think of frame sizes in three practical groups:

  • Small frames (63-112): Workshop machines, small pumps, fans and gearbox drives are in this group. The motors are light enough for one person to carry, are shipped by courier, and their installation does not require a crane. What speeds up the buying decision in this group is the abundance of stock; when you state the correct frame, it is usually on the courier the same day.
  • Medium frames (132-225): The group that carries the load of industry; conveyors, medium pumps, compressors and mixers turn in this range. The motors are shipped on pallets by freight. In this group, a frame error is the most expensive mistake, because the motor has passed the "can be adjusted by hand" size; the return logistics of a wrong product are a cost in themselves.
  • Large frames (250-355L): Crushers, large fans, mills and main drive applications. Shipment is by special vehicle, with unloading by crane or forklift. In this group, an order is not just a product but also a logistics and installation plan; the plan cannot be made without frame and shaft information.

Frame Size, Weight and Transport Planning

The frame number also tells you the motor's approximate weight class, and this information determines the shipment method. Small frames are carried in a courier box, medium frames by palletized freight, and frames 250 and above mostly by special vehicle organization. When we clarify the frame at the quote stage, we can also write the transport cost and delivery method in the same quote; this way, how the motor reaching the facility will be unloaded stops being a last-minute surprise.

Especially for large motors such as frame 355, we share details such as lifting eyes, sling points and forklift entry before shipment. If your facility has no crane, it is enough to say so when ordering; we plan the vehicle type as a truck-mounted crane and lower the motor next to its base.

Why Is Stating the Frame in the Order So Important?

A motor ordered without the frame number given can cause problems at three points:

  • Foot holes and chassis: If the frame changes, the foot hole spacing changes too. For a motor that does not fit the existing chassis, either new holes are drilled or an adapter plate is fabricated; both mean time and labour.
  • Shaft height: In belt-pulley systems, if the shaft axis height changes, the pulley alignment is thrown off; in coupled systems, the motor-pump axis alignment has to be redone.
  • Shaft diameter and key: As the frame grows, the shaft diameter grows too. If the existing coupling hub or pulley bore does not fit the new shaft, the part needs turning or a new one is bought.

The common feature of these three problems is that there is no fault whatsoever in the motor itself; the fault is in the incomplete definition of the match. What is more, these problems are often noticed on installation day, the worst possible moment: the crane is on site, the maintenance team is on overtime, the line is stopped and waiting while the motor's feet will not seat on the chassis. You can zero out these risks by sharing the type code on the nameplate before ordering. To read the nameplate data fully and transfer it correctly to the order form, you can use the checklist in our like-for-like matching with nameplate data article.

The Effect of Frame Size on Lead Time in From-Stock Delivery

Our stock management is built around frame sizes. Frames from 63 to 160 are the fastest-moving group, always on the shelf; in medium frames between 180 and 250, common power-speed combinations are kept in stock; in frames 280, 315, 315HT and 355, stock waits ready in certain combinations, while special combinations are produced on a short lead time. When you give the frame number while requesting a quote, we can tell you not just a price but a firm lead time: you learn at the moment of ordering the difference between "in stock, shipping today" and "three weeks' lead time".

Electric motor prices rise with frame size, because a growing frame means more casting, more lamination and more copper. When comparing prices, make sure both quotes reference the same frame; two sellers quoting different frames for the same kW will naturally come out at different prices. You can reach general information about our manufacturer identity and our product range covering the whole frame span from our hemmotor.com homepage; our other purchasing guides on cast iron framed motors are compiled in our cast iron framed motors blog category.

The 60-Second Pre-Order Checklist

Before sending your quote request, fill in these five lines:

  • Power: ... kW
  • Speed: 1000 / 1500 / 3000 rpm (or the value on the nameplate)
  • Frame: the number in the type code on the nameplate (e.g. 132M, 250M, 355L)
  • Mounting type: B3 / B5 / B14 / B35 / B34
  • Efficiency class: IE3 / IE4

When these five pieces of information are complete, the chance of a three-phase motor order arriving wrong is practically eliminated. If you are missing information, no problem; send the nameplate photo and let us do the matching.

For Machine Builders: Frame Standardization in Series Production

We have a special note for OEM firms producing series machines. Gathering the machines in your product range into as few frame sizes as possible makes stock management easier on both your side and ours. For example, if instead of using frames 100, 112 and 132 across three different machine models you can consolidate the design to 112 and 132, your spare parts shelves simplify, your hand strengthens in bulk purchase negotiations, and in emergency replacement scenarios you can rescue more than one machine with a single frame. On annual-volume purchases, we make frame-based framework agreements and hold reserved stock for you in the agreed frames.

The same approach applies to maintenance teams: if you draw up your facility's motor inventory by frame number, how many spares of which frame you need to keep becomes clear by itself. In the inventory exercise, our sales team can support you with a ready template.

Frequently Asked Questions

Does choosing one frame size larger at the same power make the motor more durable?

No, an unnecessarily large frame brings you cost, not durability. The motor's frame is already correctly sized for the thermal and mechanical load of the power-speed combination it is made for. Requesting one size larger is meaningful only in special cases (fit to an existing chassis, customer specification, special cooling condition). In standard applications, a correctly matched frame is the most efficient choice in terms of both price and layout.

What is the 315HT frame, and how does it differ from a normal 315?

315HT is the extended-reinforced variant of the frame at 315 shaft height for high torque/power needs, and it features in our production program in the B3 and B35 mounting types. It often comes up in high-power crusher, mill and fan drives; most of our customers ordering in this class are facilities making like-for-like replacements. If your existing motor's nameplate says 315HT, state it exactly so when ordering; the foot and package dimensions may differ from a standard 315 frame. In case of doubt, we confirm over a nameplate photo.

My old motor is a different brand; is its frame number compatible with your motors?

Yes. Because the frame number is based on the IEC standard, it is brand-independent: any brand's 160M B3 motor and our 160M B3 motor have their shaft height, foot hole layout and shaft diameter machined to the same standard. Thanks to this, you can replace your old-brand motor with a from-stock HEM Motor product without making any change to your chassis. All you need to do is give us the type code on the nameplate.

Get a Quote: The Correctly Framed Motor, First Time

Send us your frame number, your power and your speed; let us price your cast iron framed motor according to stock availability the same day and plan the shipment. You can reach our sales team at +90 (532) 345 49 86 or send your quote request through our contact us page. For motors whose nameplate is unreadable and frame is unknown, we also do the matching with a photo and a few measurements; let your motor arrive right the first time, and your production not wait.

For project-based purchases, we gather complete motor lists made up of different frame sizes into a single quote: small frames are brought forward by courier, large frames are scheduled according to production-stock status, and the shipment calendar is ordered according to your installation plan. Write the frame number on every line of your list; we will come back with a clear table including price, lead time and transport. The difference of working directly with the manufacturer shows itself precisely at this point.