On an oven line, what determines a motor's endurance is the air temperature at the point where it sits and the radiant heat reaching the frame. The rated power of IEC motors is defined for a given ambient temperature; if that limit is exceeded near the oven mouth, under a hood or inside an enclosed machine housing, the motor's location, ventilation or power margin should be reconsidered.

DRG-90S-4 1.1 kW 1500 rpm cast iron frame DRG three-phase motor – bakery oven line motor heat

Where heat concentrates on the line

  • Tunnel oven belt drive: The motor is usually at the infeed or outfeed end; hot air spilling from the oven opening can be directed straight at it.
  • Rotating rack ovens: The drive motor may be placed on the oven roof, close to the hot air outlet.
  • Cooling conveyor: Heat from product leaving the oven builds up under the belt.
  • Kneading and dough sheeting: Far from the oven, but flour dust and an enclosed housing make heat dissipation harder.

What changes in the motor as the ambient heats up?

Class F insulation sets the temperature limit the winding can withstand. As the ambient warms, the margin left for the motor's own temperature rise shrinks; the motor is then either loaded below its rated power or the next rating up is chosen. How much margin to allow cannot be stated without measuring the temperature where the motor sits. Bearing grease also ages faster at high temperature, so the relubrication interval may shorten.

Flour dust and enclosed housings

With IC411 cooling, the fan draws air from the space around the motor. If the same hot air keeps recirculating inside a closed housing, cooling suffers. Flour dust mixed with moisture sticks to the fins like dough and hinders heat removal. Leaving air inlet and outlet openings in the housing, or using an intermediate shaft or belt arrangement that moves the motor away from the heat source, are common solutions.

Information needed for the decision

  1. The highest air temperature measured around the motor
  2. The motor's distance from the oven body, the door or hot product
  3. The power and speed the machine requires
  4. Whether the housing can be ventilated

Application examples are on the industrial oven machine motors and dough kneading motors pages, and you can review models in your chosen rating in the shop.