Cri-Man TBM 1.5 / 6N, TBM 2.2 / 6N, TBMex 2.2/4, TBM 2.2/4, TBMex 3/4 Service And Maintenance Manual

“TBM” SERIES

SUBMERSIBLE HORIZONTAL

MIXERS

USE AND MAINTENANCE MANUAL

TYPE
SERIAL NUMBER
POWER
DATE

CRI-MAN S.R.L.

Via Costituzione, 50/F – 42015 Correggio (RE) – ITALY

Tel. [phone] - Fax [phone]

DIRECT:
TBM 1,5 / 6N

TBM 2,2 / 6N

WITH GEAR BOX:
ATEX STANDARD

TBMex 2,2/4 TBM 2,2/4
TBMex 3/4 TBM 3/4
TBMex 4/4 TBM 4/4
TBMex 5,5/4 TBM 5,5/4
TBMex 7,5/4 TBM 7,5/4
TBMex 9/4 TBM 9/4
TBMex 11/4 TBM 11/4
TBMex 15/4 TBM 15/4
TBMex 18,5/4 TBM 18,5/4

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

2

I N D E X

Page

1. General information

.................................................................................................................................4

2. Precautions

......................................................................................................................................................4

3. Prescriptions and general recommendations

................................................................5

4. Safety precautions

....................................................................................................................................5

4.1 Safety regulations for Atex version

.........................................................................................................6

5. Product description and use

...........................................................................................................8

5.1. Sectors for use

............................................................................................................................................... 8

5.2. Reception and nameplate exemplification

.........................................................................................8

5.3. Technical description

................................................................................................................................10

6. Transport and storage

......................................................................................................................... 14

7. Installation

.......................................................................................................................................................14

8. Electrical connections

......................................................................................................................... 15

8.1. Connection of electrical motor to control panel

.............................................................................15

8.2. Earth conductors connection

...............................................................................................................19

8.3. Engine protection connections

............................................................................................................19

9. Commissioning and operation

....................................................................................................19

9.1. Atex version

................................................................................................................................................. 158

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

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10. Prevention maintenance checks

............................................................................................ 20

11. Decommissioning and disposal

............................................................................................. 21

12. Guarantee

.....................................................................................................................................................22

13. Troubleshooting

.....................................................................................................................................22

13.1. Indications of problems

.......................................................................................................................... 22

13.2. Possible reasons for the problems

....................................................................................................22

14. Annexes

..........................................................................................................................................................23

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

4

1. GENERAL INFORMATION

The instructions provided in this manual and regarding safety are marked with this symbol.
Non complying with these warnings may expose the personnel to risks for their health.

The instructions marked with this symbol must be complied with as they mainly concern
electricity-related hazards.

WARNING Instructions accompanied by this word concern the correct operation, storage or
conditions of the equipment. This word indicates only the main precautions to be considered for safe,
correct and reliable operation together with all the indication provided by the manual.

The descriptions and drawings contained in this publication are to be intended as non-binding.
Subject to the essential features of the machine described, CRI-MAN reserves the right to make any
change to components, machine parts, details and accessories, as it will deem it appropriate for product
improvement purposes or for construction or commercial requirements, at any time and without any
obligation to update this publication.

2. PRECAUTIONS

Keep this manual with care for future reference. Copies of the mixer nameplates showing specifications
and technical operation details of the machine purchased are an integral part of this manual.
The mixers described in this manual are for farming or industrial use; therefore, the equipment shall only
be installed, operated, serviced and repaired by specifically trained and qualified personnel.

Reading this operation and maintenance manual is absolutely necessary before transporting, installing,
commissioning, operating, adjusting, assembling, disassembling and servicing the mixer.
This manual is an integral part of the product supplied. It is the Purchaser’s responsibility to instruct all
the operating personnel who will use, handle or service the equipment to carefully read and study this
manual.
The mixers described in this manual are not intended for domestic use, or the like, and must never be
left within children’s reach or, in general, within reach of any person who has not been trained to their
use, installation or maintenance.
The content of this manual applies to the serial version of the equipment; similar mixers supplied as "job
orders” may not fully correspond to the aspects described in this manual.
The supplier of this product shall not be held liable for any damage caused to persons, animals or
objects if the instructions contained in this manual have not been fully complied with.
Supplementary nameplates supplied with the mixer shall be kept together with this operation and
maintenance manual and the electric control equipment for easy and prompt consultation.
For safety reasons and to ensure that guarantee conditions are fulfilled, do not use the equipment in
case of failure or a sudden change in the product.
It is the Purchaser’s liability to provide the mixer with appropriate alarm and protection systems, as well
as to carry out the necessary checks and maintenance to prevent any accident or damage due to
malfunction.
To request further information, please contact CRI-MAN directly or call its authorized Support Centers.

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

5

3. PRESCRIPTIONS AND GENERAL RECOMMENDATIONS

- The equipment or any of its parts must not be used or operated by personnel who has not been
expressly authorised to do so.

- It is forbidden to carry out any maintenance, repair, modification operation that is not strictly
necessary for the working cycle when the machine is on. First of all, disconnect all the power inputs
of the machine.

- Do not remove any protection guards installed on the machine.

- Do not use the equipment for any purpose other than those for which it has been intended.

- When work is over, always disconnect the equipment from electrical power.

- Any maintenance operation regarding electric or non-electric parts shall be carried out in

compliance with CEI 64-8 462.2 463.1 573.3 standards.

4. SAFETY PRECAUTIONS

Any operation shall be carried out on the mixer by specifically trained and qualified personnel with the
appropriate tools and equipment in full compliance with the instructions given in this manual.
Both in the event of a new installation or for maintenance purposes, comply with all hygiene, accident
prevention and safety standards and regulations, as well as with applicable local hazard prevention
legislation. The Purchaser is liable for complying with these regulations and safety instructions.
In particular, strictly comply with the following recommendations:
System inspections

1) Considering the nature of the fluids to be processed, wear appropriate personal protection clothes

and outwear to avoid any contact of the skin with equipment or contaminated fluids.

2) The operating personnel must receive all the vaccines against any possible disease which may be

transmitted through wounds, contact or inhalation.

3) Before performing any action on the mixer, ensure that all the power cords that feed the equipment

are disconnected from the main power supply.

4) Before displacing the equipment from its location, first disconnect the power cords from the contact

boxes of the electric drive units and disconnect feed; displace the mixer with the appropriate
equipment for the purpose.

Mixer inspections

1) The mixer or any accessory must be accurately and completely cleaned with water o specific

products before any operation;

2) If the equipment is disassembled, handle the pieces with special protection gloves;

3) Check the degree of insulation of the electric motor and the efficiency of the earth connection

before conducting any electrical power test.

4) The external surface of the motor can exceed 80°C. Use any necessary device to prevent

burnings.

The mixer cannot be used:

− Before carefully reading Use and Maintenance instructions

− During mixer maintenance and repairing operations

− During tank maintenance and repairing

− During mixer placement operations

− When mixer is damaged or there is the suspicion of possible damage

− When liquid level is less than 0.5m above propeller diameter

The design of the mixer may not be altered without the permission of the manufacturer. If there is any
change in the use to which the mixer is put or in the properties of the liquid to be agitated, please
contact the manufacturer of the mixer.

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

6

4.1 Safety regulations for Atex version

TBMex mixers are designed for places in which it is possible to have specific potential explosive
athmosphere: Cri-Man assumes no liability for installations or repairs performed by non­qualified personnel and without respecting standards regarding potentially explosive
atmosphere.

Follow this indications when installing flame-proof explosion mixers:

− TBMex mixers are built in accordance with standards EN1127-1, EN13463-1, EN 13463-5, EN

13463-8, EN13980, EN60079-0, EN60079-1, in the way to be installed in presence of specific
potential explosive atmosphere.

− The classification of potentially explosive atmosphere zone gives the indication of characteristic

the equipment has to respect: verify, referring to the marking on mixer plate, directive and
harmonized standards, that the characteristics of explosion-proof mixer meet the requirement of
the classification. If not, do not install the machine.

− Install accessories in accordance with applicable standards (EN 60079-14).

− During installation and maintenance, check that the power supply is turned off and that it is not

possible to reinsert it before starting to use the mixer.

− Do not perform any maintenance before shutting down power supply or in presence of

potentially explosive atmosphere.

− Do not replace any component in the electric motor: this type of maintenance can be carried out

by Cri-Man or authorized personnel.

− The user must be aware of the chemical and physical properties of gases and/or vapors present

in explosion-protected zones, as well as the risks posed by the presence of electrical
components.

− Maintenance work on electrical equipment must be carried out in accordance with applicable

standards (EN 60079-17).

− Do not start a mixer if not totally immersed in

liquid to be processed. Starting without load for

maintenance or inspection have to be carried out in a zone not classified as potentially
explosive.

Cri-Man mixers TBMex are marked as follows:

II 2 G Ex d IIB T5 (reference EN 60079-0, EN 60079-1)
II 2 G c k T5 (reference EN 13463-1, EN 13463-5, EN 13463-8)

Legenda:

Symbol Description Note
II

Group II equipment Except from mines

2

Category 2 High level of protection

G

Presence of gas vapors or fogs

Ex

Protection in accordance with harmonized
standards

d

Flame-proof explosion protection Referred to electrical motor

IIB

For gas type B All gas except from H

2

, C2H2, CS2

T5

Temperature class Maximum surface temperature 100°C

c

Protection by constructional safety Non electrical components

k

Protection by liquid immersion Non electrical components

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

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Here below a table of correspondence between the dangerous areas for potentially explosive
atmospheres (94/9/CE), the categories (94/9/CE) and the protection level of equipment EPL (EN 60079-

0).
Before the installation of an Atex mixer, ensure that it is suitable for that zone.

Dangerous Zone Atmosphere

Cathegory

(G= gas, D= dust)

Zone 0

Continuous presence or
for long periods

1G

Zone 1

Probable arising

1G or 2G

Zone 2

Presence of gas,
vapors potentially
explosive

Non probable arising

1G, 2G or 3G

Zone 20

Continuous presence or
for long periods

1D

Zone 21

Probable arising

1D or 2D

Zone 22

Presence of clouds of
combustible dust in the
air

Non probable arising

1D, 2D or 3D

In all areas in which potential explosive atmosphere can arise, must be installed equipment in
compliance with categories identified from directive 94/9/CE (Atex).

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

8

5. PRODUCT DESCRIPTION AND USE

5.1. Sectors for use

Mixers manufactured by Cri-Man S.r.l. are ideally suited to applications involving the mixing, i.e. the
homogenizing and suspending of liquids of low to medium viscosity.

Please contact Cri-Man S.r.l. for further information on other applications, such as the mixing of viscous
media or explosive materials.

5.2. Reception and nameplate exemplification

In the event of damage, please contact the nearest service center or the manufacturer.
Check that the received material correspond to what indicated in transport document and that it is not
damaged.

WARNING This machine may not be operated under conditions which exceed either the threshold
values stated on the factory specification plate, or any other instruction

s contained in the operating

regulations or the contractual documentation. All prescribed electrical connection figures, as well as all
installation and servicing instructions, must be adhered to without exception. Any use of the machine
which exceeds the conditions contained in the operating manual can result in the failure of the machine.
Non-compliance with this warning can result in personal injury and material damage.

Note :

All descriptions and instructions in this guide are based on standard models. These operating
regulations do not take into account all details and variations in design and construction nor any
possible eventualities or events that may occur during erection, operation or servicing.

These operating regulations do not take any local safety regulations into account. The operator of this
installation is responsible for ensuring that such regulations are adhered to and that they are followed by
the installation personnel who install the mixer.

The type plate on the casing identifies the type of mixer, the most important operating data and the
machine number or serial number respectively. These details must always be given when information is
required, when reordering machines or spare parts.

In the event of damage, please contact the nearest service center or the manufacturer.

The factory plate on the casing identifies the type of mixer, the most important operating data and the
machine number or serial number respectively. These details must always be given when information is
required, when ordering machines or spare parts.

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

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Mixer plate

TBM standard

Via Costituzione, 50F
42015 Correggio (RE) Italy
Tel. [phone]

x

II 2 G Ex d IIB T5 Gb

II 2 G c k T5

0948

Matricola / N°

non aprire se in tensione / do not open when energized

ISSeP 13 ATEX034

TBMex

Tipo : Complete electric mixer code
Atex : Complete Atex code
Matricola : Serial Number: first numbers indicate year of production

PN [kW]

: Electrical motor Power

: Alternate current
Hz : Frequency
Cos Ø : Power factor
avv. : Type of starting allowed
S1 : Continuous service
V : Electrical motor voltage
IP68 : Motor protection level
I

N

[A] : Rated absorption
cl. F : Insulation class
Q [l/se] : Capacity

N°

poli

: Numbers of poles

g/min : RPM propeller

For safe and proper operation, must not be exceeded maximum performance
characteristics described on mixer’s plate.

[A]

I

N

P

N

[kW]

Tipo

avv.

V

Matricola

Hz

cosØ

n

°

poli

g/min

Q [l/sec]

H [m]

Via Costituzione, 50F
42015 Correggio (RE) Italy
Tel. [phone]

RoHS

2002/95/EG

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

10

5.3. Technical description
General information

Manifacturer: Cri-Man S.r.l.
Type of mixer: Submersible horizontal mixer direct and with gear box, standard and

Atex version
Type designation: (TBM .../6) (TBM .../4) (TBMex …/4)
Power cable: 10.0 meters (standard length, suitable for basins up to

7 meters depth)
Corrosion protection mixer: Painted with two component epoxy resin with substrate with zinc

phosphate

Motor

Manifacturer: Cri-Man S.r.l.
Protective system: IP 68 a 20 m
Insulation class: F
Sealing: Radial mechanical seal
Motor casing material: Cast iron, EN GJL 250

Gearbox

Manifacturer: Cri-Man S.r.l.
Type: Planetary gearbox
Gears: Hardened and ground
External sealing: 2 radial shaft sealig rings
Internal sealing: Mechanical seal
Shaft bearings: 2 taper roller bearings
Gearbox casing: Cast iron, EN GJL 250

Propeller

Number of blades: 2 - 3
Propeller diameter 290 - 780 mm
Material: Stainless steel

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

11

Mixers type TBM .../6N

Type TBM…/6 mixers are available in following configurations:

Mixer type: TBM 1.5/6N TBM 2.2/6N

Motor:

Motor size 100 100
Mech. nom. rating 1.5 [kW] 2.2 [kW]
Electr. actual power [kW] 1.97 2.90
Nominal speed [rpm] 925 940
Rated current

1)

[A] 4.2 5.9

Power Factor [cos Ø]

0.75 0.73
Operating mode S1, Y S1, Y
Mains voltage [V] 3 x 400 3 x 400
Permissible motor voltage [V] 230/400 230/400
Mains frequency required [Hz] 50 50
Starting type Y Y

Propeller:
Number of blades 3 3
Diameter [mm] 297 347
Capacity

1)

[m3/h] 643 876

Propeller speed [rpm] 925 940

General data:
Axial thrust force

1)

[N] 230 313

Output torque

1)

[Nm] 15.2 22.4

Weight with console [in kg] 54 57

1)

in clean water. Values obtained in accordance with ISO 21630.

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

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Mixers type TBM .../4, TBMex…/4

Type TBM .../4, TBMex…/4 mixers are available in the following configurations:

Mixer type: TBM 2.2/4 TBM 3/4 TBM 4/4 TBM 5.5/4N TBM 7.5/4N
TBMex 2.2/4 TBMex 3/4 TBMex 4/4 TBMex 5.5/4 TBMex 7.5/4

Motor:

Motor size 100 100 100 132 132
Mech. nom. rating 2.2 [kW] 3.0 [kW] 4.0 [kW] 5.5 [kW] 7.5 [kW]
Electr. actual power [kW] 2.80 3.60 4.85 6.50 8.80
Nominal speed [rpm] 1420 1420 1405 1430 1440
Rated current

1)

[A] 5.3 6.8 9.1 12.5 15.8

Power Factor [cos Ø]

0.78 0.78 0.78 0.85 0.85
Operating mode S1, Y S1, Y S1, ∆ S1, ∆ S1, ∆
Mains voltage [V] 3 x 400 3 x 400 3 x 400 3 x 400 3 x 400
Permissible motor voltage [V] 230/400 230/400 400/690 400/690 400/690
Mains frequency required [Hz] 50 50 50 50 50
Starting type Y Y Y∆ Y∆ Y∆

Gearbox :
Reduction 4.39 4.39 4.39 4.39 4.39
Output speed [g/min] 323 323 320 326 328

Propeller:
Number of blades 2 2 2 2 2
Diameter [mm] 445 460 515 535 585
Capacity

1)

[m3/h] 1333 1581 2146 2391 3254

General data:
Axial thrust force

1)

[N] 441 580 853 981 1520

Output torque

1)

[Nm] 65 87 119 161 218
TBM weight [kg] 75 78 81 109 115
TBMex weight [kg] 77 80 83 112 118

1)

in clean water. Values obtained in accordance with ISO 21630.

Mixers in Atex version (TBMex…) are manifactured in accordante with standards:
EN60079-0 and EN 60079-1. Type: II 2G Ex d IIB T5 Gb
EN13463-1, EN13463-5, EN13463-8. Type II 2G c k T5

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

13

Mixer type

: TBM 9/4N TBM 11/4 TBM15/4N TBM 18.5/4N

TBMex 9/4 TBMex 11/4 TBMex 15/4 TBMex 18.5/4

Motor:

Motor size 132 160 160 160
Mech. nom. rating 9 [kW] 11 [kW] 15 [kW] 18.5 [kW]
Electr. actual power [kW] 10.8 12.5 16.8 20.0
Nominal speed [rpm] 1440 1450 1450 1450
Rated current

1)

[A] 19.0 23.5 30.0 36.0
Power Factor [cos ϕ] 0.83 0.81 0.83 0.83
Operating mode S1, ∆ S1, ∆ S1, ∆ S1, ∆
Mains voltage [V] 3 x 400 3 x 400 3 x 400 3 x 400
Permissible motor voltage [V] 400/690 400/690 400/690 400/690
Mains frequency required [Hz] 50 50 50 50
Starting type Y∆ Y∆ Y∆ Y∆

Gearbox :
Reduction [-] 4.39 4.13 4.13 4.13
Output speed [g/min] 328 351 351 351

Propeller:
Number of blades [-] 2 2 2 2
Diameter [mm] 595 600 720 780
Capacity

1)

[m3/h] 3628 3977 5335 6884

General data:
Axial thrust force

1)

[N] 1826 2158 2697 3826

Output torque

1)

[Nm] 261 299 408 503
TBM weight [kg] 123 183 193 203
TBMex weight [kg] 126 187 197 207

1)

in clean water. Values obtained in accordance with ISO 21630.

Mixers in Atex version (TBMex…) are manifactured in accordante with standards:
EN60079-0 and EN 60079-1. Type: II 2G Ex d IIB T5 Gb
EN13463-1, EN13463-5, EN13463-8. Type II 2G c k T5

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

14

6. TRANSPORT AND STORAGE

The mixer may only be lifted using the suspension points provided.
The winch or lifting tackle supplied incl. the chain or cable to raise and lower the mixer in the basin may not
be used as a universal form of lifting equipment.

Never hang the motor cable to handle the mixer!

ATTENTION During transport and storage, keep the machine fixed on its base support; be sure that it is
well fixed in order to avoid falls that could cause damage to things, people or to the machine.

Receipt of goods

The shipment must be inspected for damage immediately on arrival. If necessary, a damage claim form must
be completed in the presence of the haulage operator/driver since remedying any damage free of charge is
otherwise impossible.

Storage

If the mixer has to be stored, it is essential to select a storage area that is free from oscillations and vibration
in order to prevent the roller bearings from being damaged. The machine must also be stored on dry
premises in which the ambient temperature is not subject to major fluctuations.

If the mixer has had to be stored for more than one year, the gearbox oil must be replaced. This must also
be done even if the machine has never been in use previously. (Natural aging of mineral oil lubricants).

7. INSTALLATION

All stainless steel threads must be greased in advance with a suitable paste.
Always ensure that installation and fitting tools (cutoff disks, open-ended wrenches, screwdrivers,

files, etc.) are strictly separated for use with stainless steel parts and normal steel parts. If this is
not done, microscopic rust particles on these tools can be pressed into the stainless steel parts where they
will trigger off a corrosive reaction that can lead to their destruction in time.

Installation must be in accordance with all local safety regulations. CRI-MAN cannot accept any

liability due to improper mounting of the machine.

The fully assembled machine must be positioned and rigidly fixed using its fixing holes. In case
(recommended) use of Cri-Man equipment, refer to installation instructions.

Use and Maintenance instructions

Submersible horizontal mixers

“ TBM “ series

Release 03 / 2014

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8. ELECTRICAL CONNECTIONS

8.1. Connection of electrical motor to control panel

DANGER!

The voltage-carrying and rotating parts of electric machines can cause severe or fatal injuries.
Installation, connection, commissioning as well as servicing and repair work may only be carried out by
qualified technicians with due regard for:

− these instructions

− all other project documentation relating to the drive, commissioning instructions and electrical

− all currently valid national and local regulations relating to safety and accident prevention

As a principle all electrical connections must be carried out by a qualified electrician.
All electrical connection necessary to operate the mixer are responsibility of the installer, who also has the
responsibility to ensure that the control panel is in accordance with National rules, and that it has an
adequate degree of protection with respect to installation area. Install electrical equipment in dry area.
Otherwise make use of special equipment.

Electrical motor characteristics are indicated on data plate.
The mixer is supplied complete of connection to mains. The core code numbers are indicated along the
corresponding cores (s. connection diagram in 8.3.4).

Before connecting the motor, the actual operating voltage must be compared with the voltage data on the
motor specification plate and with the motor windings. Please refer to Fig. 8.3.

WARNING After ensuring the electric connection, ensure that the direction of rotation is correct: watching
the mixer from the back side of the motor, the propeller must rotate clockwise. In order to reverse the
direction of rotation, exchange two phases.
Three phases conductor (L1, L2, L3) must not be confused with neutral conductor (N) or earth conductor
(yellow-green).
Do not change the position of cables coming from the electrical motor to the terminal board (U1, V1, W1, or
U2, V2, W2) to avoid errors in Y-∆ starting system.

WARNING Undersized or poor-quality electrical equipment may undergo rapid contact deterioration and
consequently power the motor incorrectly, which may damage the equipment. In order to ensure safe
operation, install good-quality electrical equipment.

WARNING The use of inverters or soft-starters, if not correctly planned and implemented, could damage
the mixer, not only in its electrical components but also the mechanical elements.
If the associated problems are not fully understood, request assistance from the Cri-

Man

Technical Offices.
Operation with Inverters or Soft-starters:

The structure and motor insulation used are suitable for use with Inverters and Soft-starters but some
essential operating conditions must be satisfied:

- Comply with the electromagnetic compatibility directives.

- The lower threshold frequency must be regulated so that the machine does not operate below 30 Hz.

- The upper frequency threshold must be regulated so that the nominal motor power is not exceeded

(max frequency 50 Hz).

The most recent inverters operate at high repetition frequencies and with sharp increases in voltage ramp.
This reduces power losses and motor noise but generates sharp voltage peaks in the motor coil. These
voltage peaks negatively influence the duration of transmission, relative to the operating voltage and the
cable length between the motor and inverter. The voltage ramp dU / dt, typical of a PWM inverters, must be
lower than 1 kV / µs. In general this value does not affect traditional asynchronous motors, like those used in
the TBM series mixers, if the cable has a length less than 40 to 50m. In any case it is good practice to fit at
least three sinusoidal filters between the motor and inverter and if the cable is longer than stipulated above
other types of filters are required.