November 2019

Two key factors are critical when using mobile equipment: on the one hand, the available power must be enough for the task, and on the other hand the on-board energy supply must be sufficiently dimensioned for the job to be performed and it must be possible to “top it up” quickly. In the case of autonomous electric mobility with a power supply based on batteries, this is a demanding task. Durable, maintenance-free drives specially designed for battery-powered mobile drive solutions, such as off-road motorbikes or smooth running road sweepers, represent a challenge for engineers.

These days, electric systems are the most environmentally friendly technology for drives. New magnet materials allied to sophisticated computer-based simulation enable power densities and torque curves to be achieved that significantly surpass those of combustion engines with the same weight and space. Where achieving the highest possible torque with a low height and a high efficiency is important, modern synchronous disc-type motors are the ideal solution. However, mobile machines have demanding requirements in terms of the drive technology. As well as offering a long operation time and range, the drives need to be powerful and compact. HEINZMANN has responded to this challenge with its PMS 212 and PMS 215 synchronous motors, which offer a 30 % reduction in size and an increased torque, along with improved efficiency. These are features that often deliver crucial benefits in practical use. Depending on the inverter used, 4-quadrant operation with regeneration is also possible, further increasing the range.

Brushless sweeping and movement

With their excellent performance values, the new motors provide significant improvements, e.g. for mobile use in a wide range of different areas. The advantages for municipal vehicles, i.e. urban road sweepers, lie more in the greater efficiency, the very low operating noise and the higher degree of protection. In the case of a fully electric, battery-powered road sweeper with 2 m³ waste tank with 1.5 t load, in practice this means a 10 dB or around 75 % reduction in noise compared to a diesel engine drive. In addition, the frequency range is more comfortable for human hearing. The average CO2 savings are around 26 t per year compared to a conventional diesel drive and there is no unpleasant smell. The EC disc-type motors allow up to eight hours of operating time and can move the vehicle over gradients of up to 30 % with no problems. In pure driving mode, a speed of around 40 km/h can be achieved, more than enough for use in urban areas to get to more distant areas of use without losing time. Incidentally, the maintenance-free drives reduce operating costs by around 75 % compared to more maintenance-intensive diesel models.

Mobile EC drive technology

What is the basis for these application-dedicated optimised drives? For moving systems, the general rule is that the less mass has to be moved, the lower the energy required to do so. At the same time, the dynamics improve with the same energy input, i.e. faster acceleration and braking are possible. Of course, this fact also applies to the motors themselves, e.g. the lighter the rotor the more agile the drive’s acceleration. Double-acting disc-type motors are particularly well suited for dynamic movement sequences, as firstly they have low mass - i.e. they have a very compact construction - and secondly, depending on type, the comparatively large rotor diameter provides a high torque with excellent material utilisation. The two-sided coil arrangement allows efficient utilisation of the magnets, resulting in a correspondingly high power density with good cooling potential. The patented rotor design, with features including high-performance permanent magnets, reduces the inertia and detent torque. This makes the motors the first choice for dynamic drive solutions, particularly because they can tolerate significant transient overloads up to 400 %. The synchronous machines provide a broad speed and power range with very good control options. For mobile operation with batteries, the high efficiency guarantees a long running time, while in stationary use it reduces the CO2 footprint of the application.

Well cooled for great power and efficiency

Losses in electric motors generate heat. In turn, the increased temperatures cause both the insulating lacquer on the coil and the lifetime grease filling of the ball bearings to age more quickly; as a result electric motors must be able to dissipate their waste heat as effectively as possible. In addition, as the temperature rises the resistance of the copper coil increases, leading to greater power loss and lower efficiency. So there were numerous good reasons for the motor manufacturer to optimise the air cooling. As a result, the bearing covers on the two synchronous motors have been completely redesigned. Reinforcing bars have significantly improved cooling and stability and the motor width has been reduced by around 30 mm. In turn, the better cooling provides a power increase of around 30 % at the same temperature level. For the near future, a further increase in power is planned by raising the motor speed from 6,000 to between 8,000 and 10,000 rpm. If peak power is not required, the lower overall operating temperature improves the service life of the coil and bearings.

Suitable for everyday use, robust even off-road

In electric motors, the service life of the bearings depends on more than just the temperature; sealing against liquid and dust - in other words protection against ambient conditions - also plays a significant role. Thanks to a completely redeveloped seal, the rotor bearings are now protected against the effects of even extreme dirt. Particularly off-road or in stirred up road dust, this considerably increases the operating time. In conjunction with the redesigned connection box, the motors now meet the requirements for the IP6K9K degree of protection, which means they are equipped for harsh mobile applications. As a consequence, e-vehicles in off-road use benefit from the better seal. The bearings are dust proof and protected against both contact and ingress of water during high pressure or steam jet cleaning after use. In addition, this mobile application calls for a high torque, dynamic behaviour and, last but not least, high efficiency; the PMS 212 and PMS 215 synchronous motors meet these requirements optimally.

The improved seal does not change anything for the designer - all connection dimensions are identical to previous models. The new housing covers even allow simple customer-specific adaptation. If the connection diameter of the centring flange or the threaded attachment holes differs from the standard, pitch circles from 55 to 83 mm for the flange and between 105 and 190 mm for the threaded holes can now be produced. The redesigned connection box also provides internal wiring for a star/delta switch and is now only fitted with three power cable connections (U, V, W) and one sensor cable connection externally. The possible power cable cross-section has been increased to minimise the power loss due to high currents (up to 250 A permanent current at 48 V / 10 kW, transient starting current up to 1,200 A).

The evolutionary improvements mean that the two new powerful compact drives offer continuous power of 9 or 15.5 kW on the shaft with a diameter of 230 or 274 mm and a width of 117 or 154 mm (PMS 212 and PMS 215 respectively). Depending on the application or choice of battery, the supply voltage can be between 48 and 560 VDC. If required, the relevant batteries for mobile operation can quickly be recharged with a high power, considerably reducing interruptions in operation. Modern EC disc-type motors allow a wide range of applications to switch to environmentally friendly, zero emission drives. Thanks to their robust construction, high efficiency, high starting torque and good overload capability, they get mechanical systems moving even in very demanding applications.

 

PMS 212

The new generation of motors features a strongly ribbed housing with excellent heat dissipation.

(Source: Heinzmann GmbH & Co. KG)

PMS 212 SeitenansichtThe new connection box complies with IP6K9K degree of protection and allows larger copper cross-sections for a low-loss power supply.

(Source: Heinzmann GmbH & Co. KG)

Kommunalfahrzeug

Advantages for municipal vehicles driven by PMS 2nd generation lie in greater efficiency, the very low operating noise and the higher degree of protection.

 

(Source: Heinzmann GmbH & Co. KG)

PMS Water-AttackIn conjunction with the redesigned connection box the motors now meet the requirements for the IP6K9K degree of protection.

(Source: Heinzmann GmbH & Co. KG)


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