Three-Phase Electric Motor and Gearbox Compatibility on a Dough Kneading Machine

On a dough kneading machine, the spiral or fork arm folds the dough with a slow but powerful movement; on most models the bowl also turns about its own axis. This need for low speed and high torque means the motor almost always works through a gearbox or a belt-and-pulley stage. When replacing the motor, you therefore have to look not only at the motor itself, but also at how it connects to the gearbox, at the resistance of the dough at start-up and at the humidity of the bakery environment. In this article we explain, step by step, how to match a three-phase motor and gearbox on a dough kneading machine.

Power flow in a kneading machine

Kneading machines used in commercial bakeries and pastry shops have two drive groups: the main drive that turns the kneading arm and the second drive that turns the bowl. On some machines both are fed from the same motor through belt and gear stages; on others each group has its own motor.

• Motor: Usually a 4-pole three-phase motor in the 1,500 rpm class; its nameplate speed under load is around 1,450 rpm.
• Gearbox or belt stage: Reduces the motor speed to the low speed the arm needs and increases torque by the same ratio.
• Kneading arm and bowl: They carry the resistance of the dough; this resistance varies with dough stiffness, water content and how full the bowl is.

In a replacement, the motor's place in this chain must be kept: the same speed, the same connection and the torque the gearbox expects.

Three checks when connecting a motor to a gearbox

On geared kneading machines, the motor usually sits directly on the gearbox input flange. For this connection to work without problems, the following three dimensions must be the same as on the old motor:

• Flange: The spigot diameter, pitch circle and number of holes at the gearbox input must match the motor flange. A B5 flange has large through holes, a B14 flange small tapped holes; having the same name does not mean having the same dimensions.
• Shaft: The diameter, length and keyway of the motor shaft must fit the gearbox input bore.
• Frame size: If the old motor's IEC frame size (such as 100L, 112M) is the same as the new motor's, the flange and shaft dimensions are also expected to be the same; this must still be confirmed with the technical drawing.

If this connection follows standard IEC dimensions, a standard three-phase motor can be used directly. If the machine builder made the motor integrated with the gearbox, on a non-standard shaft or flange, a special motor is needed; in that case the right way is to ask with the nameplate and photos of the shaft and flange. More information on gearbox input flange compatibility is on the motors for gearboxes page.

HEM Motor models do not list the mounting arrangement per model. Foot, flange, combined and vertical options are provided according to frame size, and the flange size is verified during the order. You can compare dimensions in the 2D technical drawings and the 2026 technical catalogue.

Starting load and two speeds

A kneading machine is often started with a full bowl. Cold, stiff dough puts high resistance on the motor in the first seconds. That is why starting behaviour matters:

• Direct-on-line starting: Starting torque is high; common at small powers. Motors with a 230/400 V (Δ/Y) nameplate are connected in star on a 400 V supply.
• Star-delta starting: It lowers the starting current but also reduces the starting torque. It can strain the motor when starting with a full bowl. Motors with a 400/690 V (Δ/Y) nameplate are suitable for this method.
• Starting with a drive: Provides soft starting and speed adjustment. Our three-phase series are suitable for speed adjustment with a frequency inverter; if the motor will run at low speed with full torque for long periods, an external fan may be needed, and if the drive cable is long, a dv/dt or sine filter is considered. State these conditions in the order; details in the inverter question.

Many kneading machines have two speeds: slow mixing and fast kneading. If these two speeds are provided by a drive or by a two-stage gearbox, a standard motor is suitable. If the speeds are obtained with two separate windings inside the motor, that is, if the motor nameplate shows two powers and two speeds, it is a two-speed motor and is not treated as the same as a standard motor. For such a motor, a special motor should be enquired about with a nameplate photo.

Bakery environment: flour dust, humidity and cleaning

In bakeries there is fine flour dust in the air, humidity rises from the proofing area and machines are frequently wiped clean. All HEM Motor models on sale have IP55 protection; they are protected against harmful dust build-up and light water spray from different directions. Washing the motor directly with pressurised water or a hose is outside the scope of this class; for cleaning, wiping the motor with a damp cloth and regularly removing flour build-up from the fan cover is enough.

The motor of a kneading machine is usually inside the body, in a compartment that does not come into contact with the dough. The motor has no surface in direct contact with food; for this reason the article makes no claim of suitability for food contact. If a stainless frame or a special surface is required, discuss this separately with the machine builder and with us. For general information on food and packaging machines, see the packaging and wrapping machine motors page.

Power selection and example models

Without knowing the bowl capacity, dough type, arm type and daily operating time, an exact power cannot be stated for a kneading machine. In a replacement, the most reliable reference is the nameplate of the old motor that has worked without problems on the machine. The following 1,500 rpm models are examples of power classes often seen on commercial kneading machines:

• 2.2 kW aluminium 100L1-4: 4 poles, 1,450 rpm, IEC 100L, 230/400 V (Δ/Y), 4.52 A, 14.5 Nm.
• 3 kW aluminium 100L2-4: 4 poles, 1,450 rpm, IEC 100L, 230/400 V (Δ/Y), 6.02 A, 19.8 Nm.
• 4 kW aluminium 112M-4: 4 poles, 1,450 rpm, IEC 112M, 400/690 V (Δ/Y), 7.95 A, 26.3 Nm.

In an enclosed and clean bakery environment, an aluminium frame is a light and practical option; in layouts where the motor hangs on the gearbox by its flange, lightness also makes mounting easier. All models have class F insulation. The current price is shown on each model's own product page.

Example: replacing the motor on a spiral mixer

This scenario is hypothetical and does not describe a real customer application. On a kneading machine with a spiral arm, the motor is connected to the gearbox input flange; the old motor's nameplate reads 3 kW, 1,450 rpm, 100L frame and 230/400 V. The two speeds of the machine are provided by a drive in the panel.

• As the nameplate shows a single power and a single speed, the motor is not a two-speed motor; a standard motor can be considered.
• The values match the aluminium frame 100L2-4 model.
• The spigot diameter and pitch circle of the gearbox input flange are compared with the 100L flange on the technical drawing; the shaft bore and keyway are measured.
• On a 400 V supply the motor is connected in star; the drive parameters are entered according to the new motor's nameplate values.
• At the first start, the direction of rotation of the arm is checked; a short test is run with the bowl empty.

If the flange size had not matched, or if the shaft had been integrated with the gearbox, a special solution would have been enquired about with the nameplate and photos instead of proceeding with a standard motor.

Information you need to send us

• A photo of the old motor's nameplate; power, speed, voltage, current and frame size must be readable
• Photos of the gearbox input and the motor flange
• Mounting arrangement (flange, foot, vertical) and mains voltage
• Starting method; whether the two speeds come from a drive or from the motor windings
• Bowl capacity and the humidity and dust conditions in the bakery

You can see three-phase models that may suit a dough kneading machine and their prices on the buy electric motors page. To determine the equivalent of your old motor together, send the nameplate photo; for other questions, visit our contact page.