DM300022 Microchip Technology, DM300022 Datasheet - Page 20

• Manufacturer Part Number: DM300022
• Description: MODULE PWR DSPICDEM MC1L LV 3PHS
• Manufacturer: Microchip Technology

Specifications of DM300022

• Main Purpose: Power Management, Motor Control
• Embedded: Yes, MCU, 16-Bit
• Utilized Ic / Part: dsPIC33FJxxxMC
• Primary Attributes: 3-Phase Low Voltage Power Module
• Secondary Attributes: Motion Sensor Inputs: Hall Sensors or Optical Encoder
• Silicon Manufacturer: Microchip
• Silicon Core Number: DsPICDEM MC1L
• Kit Application Type: Power Management - Motor Control
• Application Sub Type: 3 Phase Motor
• Silicon Family Name: Piccolo
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

dsPICDEM™ MC1L 3-Phase Low Voltage Power Module
1.3
1.4
DS70097A-page 14
DC POWER SUPPLY REQUIREMENTS
CURRENT AND POWER LIMITATIONS
1.2.9
If the user is operating a brushless permanent magnet motor using field weakening by
employing phase advance, great care should be taken. If a FAULT trip occurs, firing
will stop, and the full back EMF magnitude, due to the motor's speed, will be present
on the output terminals. Should the peak of the back EMF be above the DC bus,
sudden uncontrolled motor braking will occur. The DC bus will rise in an uncontrolled
manner possibly causing damage to the power devices, DC bus capacitors and the
DC input supply. A speed greater than that which would produce a peak back EMF of
greater than 63V, with no field weakening, should not be used. This will protect the
power module, but the user should check the rating of their DC supply.
The same care should be taken with separately excited brushed DC motors if employ-
ing field weakening at high speed. If the field current were to be increased in error, a
similar braking phenomenon will occur if the back EMF rises above the DC bus. The
effect is likely to be less severe as a DC over-voltage will occur tripping out both the
armature and field supply (assuming the field is not supplied separately). For this
reason, if using a separately excited DC motor, it is recommended that both the field
and the armature are supplied from the unit.
The user's DC power supply must be electrically isolated from the AC supply. The -DC
bus is connected to ground internally within the power module. This ensures that the
DC supply has a fixed potential with respect to ground rather than floating.
Typical DC power supplies are configured to only source current. If using such a
power supply when generating/braking, the brake chopper should be used to dissipate
the returned energy. The regulation voltage for the brake chopper will be slightly
above the DC power supply. This ensures that when braking occurs there is a
seamless transition between power being drawn from the supply and power being
dissipated by the brake chopper. The user should check that damage will not occur to
the DC power supply when this higher voltage is present on its output. If this is of
concern, then the user should fit a series diode of suitable current and voltage rating
between the DC supply and the DC input to the system. Clearly, if a battery supply is
used, energy can be returned to it by recharging. However, the user should ensure
that maximum recharge rates are not exceeded and that suitable ventilation is used.
1.4.1
The maximum power and current capability of the system is dictated by the allowable
temperature rise of the different components. Establishing maximum limits is not
simple given the host of different ways the user may use the system. The voltage and
the nature of the electrical load used both affects the dissipation that occurs. In
determining the allowable limits for the power semiconductors, the following
assumptions have been made:
• Heat sink is at 70°C (worst case over temperature trip point)
• Thermal resistance of the insulating thermal pad is 4°C/W
Note that the maximum output power of the system will always be the lower value due
to the DC input stage or the inverter output stage.
Field Weakening
Introduction
© 2003 Microchip Technology Inc.